PolyORB User's Guide
********************

   PolyORB User's Guide

   Version GPL 2012-20120509 (rev. 189588)

   $Date: 2012-02-10 09:19:19 -0500 (Fri, 10 Feb 2012) $

   Robert Duff, Je'ro^me Hugues, Laurent Pautet, Thomas Quinot, Samuel
Tardieu

   Copyright (C) 2003-2012, Free Software Foundation

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU Free Documentation License", with the
Front-Cover Texts being "PolyORB User's Guide", and with no Back-Cover
Texts.  A copy of the license is included in the section entitled "GNU
Free Documentation License".

Table of Contents
*****************

PolyORB User's Guide
About This Guide
  What This Guide Contains
  Conventions
1 Introduction to PolyORB
  1.1 Introduction to distributed systems
    1.1.1 Using OS Network Services
    1.1.2 Using a Middleware Environment
    1.1.3 Using a Distributed Language
  1.2 Distribution models and middleware standards
  1.3 The PolyORB generic middleware
2 Installation
  2.1 Supported Platforms
  2.2 Build requirements
  2.3 Build instructions
  2.4 Additional instructions for cross platforms
  2.5 Building the documentation and PolyORB's examples
  2.6 Build Options
  2.7 Compiler, Tools and Run-Time libraries Options
  2.8 Platform notes
3 Overview of PolyORB personalities
  3.1 Application personalities
    3.1.1 CORBA
    3.1.2 Distributed Systems Annex of Ada (DSA)
    3.1.3 Message Oriented Middleware for Ada (MOMA)
    3.1.4 Ada Web Server (AWS)
  3.2 Protocol personalities
    3.2.1 GIOP
    3.2.2 SOAP
4 Building an application with PolyORB
  4.1 Compile-time configuration
    4.1.1 Tasking runtimes
    4.1.2 Middleware tasking policies
    4.1.3 Sample files
  4.2 Run-time configuration
    4.2.1 Using a configuration file
    4.2.2 Using environment variables
    4.2.3 Using the command line
    4.2.4 Using a source file
  4.3 Setting up protocol personalities
    4.3.1 Activating/Deactivating protocol personalities
    4.3.2 Configuring protocol personality preferences
  4.4 Activating debugging traces
  4.5 Tracing exceptions
  4.6 `polyorb.gpr'
  4.7 `polyorb-config'
5 Tasking model in PolyORB
  5.1 PolyORB Tasking runtimes
    5.1.1 Full tasking runtime
    5.1.2 No tasking runtime
    5.1.3 Ravenscar tasking runtime
  5.2 PolyORB ORB Tasking policies
    5.2.1 No Tasking
    5.2.2 Thread Pool
    5.2.3 Thread Per Session
    5.2.4 Thread Per Request
  5.3 PolyORB Tasking configuration
  5.4 PolyORB ORB Controller policies
    5.4.1 No Tasking
    5.4.2 Workers
    5.4.3 Half Sync/Half Async
    5.4.4 Leader/Followers
  5.5 PolyORB ORB Controller configuration
6 CORBA
  6.1 What you should know before Reading this section
  6.2 Installing CORBA application personality
  6.3 IDL-to-Ada compiler
    6.3.1 Usage of `iac'
    6.3.2 Usage of `idlac'
    6.3.3 Difference between idlac and iac
  6.4 Resolving names in a CORBA application
    6.4.1 `po_cos_naming'
    6.4.2 Registering the reference to the COS Naming server
    6.4.3 Using the COS Naming
  6.5 The CORBA Interface Repository
    6.5.1 `po_ir'
    6.5.2 Using the Interface Repository
  6.6 Building a CORBA application with PolyORB
    6.6.1 `echo' example
      6.6.1.1 IDL definition of an `echo' object
      6.6.1.2 Implementation code for the `echo' object
      6.6.1.3 Test code for client and server nodes
      6.6.1.4 Compilation and execution
    6.6.2 Other examples
  6.7 Configuring a CORBA application
    6.7.1 Configuring PolyORB
    6.7.2 Configuring GIOP protocol stack for PolyORB
    6.7.3 Configuring Security services for PolyORB
      6.7.3.1 Supported mechasnisms
      6.7.3.2 Compile-time configuration
      6.7.3.3 Run-time configuration
    6.7.4 Command line arguments
  6.8 Implementation Notes
    6.8.1 Tasking
    6.8.2 Implementation of CORBA specifications
    6.8.3 Additions to the CORBA specifications
    6.8.4 Interface repository
    6.8.5 Policy Domain Managers
    6.8.6 Mapping of exceptions
    6.8.7 Additional information to `CORBA::Unknown'
    6.8.8 Internals packages
  6.9 PolyORB's specific APIs
    6.9.1 `PolyORB.CORBA_P.CORBALOC'
    6.9.2 `PolyORB.CORBA_P.Naming_Tools'
    6.9.3 `PolyORB.CORBA_P.Server_Tools'
7 RT-CORBA
  7.1 What you should know before Reading this section
  7.2 Installing RT-CORBA
  7.3 Configuring RT-CORBA
    7.3.1 `PolyORB.RTCORBA_P.Setup'
  7.4 `RTCORBA.PriorityMapping'
  7.5 RTCosScheduling Service
    7.5.1 Overview
    7.5.2 `RTCosScheduling::ClientScheduler'
    7.5.3 `RTCosScheduling::ServerScheduler'
8 Ada Distributed Systems Annex (DSA)
  8.1 Introduction to the Ada DSA
    8.1.1 Architecture of a Distributed Ada Application
    8.1.2 Categorization Pragmas
    8.1.3 Pragma Declared Pure
    8.1.4 Pragma Remote_Call_Interface
      8.1.4.1 Overview of Pragma Remote_Call_Interface
      8.1.4.2 Regular Remote Subprograms (RCI)
      8.1.4.3 Remote Access to Subprograms (RAS)
      8.1.4.4 Remote Access to Class Wide Types (RACW)
      8.1.4.5 Summary of Pragma Remote_Call_Interface
    8.1.5 Pragma Remote_Types
      8.1.5.1 Overview of Pragma Remote_Types
      8.1.5.2 Distributed Object
      8.1.5.3 Transmitting Dynamic Structure
      8.1.5.4 Summary of Remote Types Units
    8.1.6 Pragma Shared_Passive
      8.1.6.1 Overview of Pragma Shared_Passive
      8.1.6.2 Shared and Protected Objects
      8.1.6.3 Summary of Pragma Shared_Passive
    8.1.7 More About Categorization Pragmas
      8.1.7.1 Variables and Non-Remote Access Types
      8.1.7.2 RPC Failures
      8.1.7.3 Exceptions
      8.1.7.4 Pragma Asynchronous
      8.1.7.5 Pragma All_Calls_Remote
      8.1.7.6 Generic Categorized Units
      8.1.7.7 Categorization Unit Dependencies
  8.2 Partition Communication Subsystem
    8.2.1 Marshalling and Unmarshalling Operations
    8.2.2 Incorrect Remote Dispatching
    8.2.3 Partition Ids
    8.2.4 Concurrent Remote Calls
    8.2.5 Consistency and Elaboration
    8.2.6 Abortion and Termination
  8.3 Most Features in One Example
  8.4 A small example of a DSA application
  8.5 Building a DSA application with PolyORB
    8.5.1 Introduction to PolyORB/DSA
    8.5.2 How to Configure a Distributed Application
    8.5.3 Gnatdist Command Line Options
    8.5.4 The Configuration Language
      8.5.4.1 Language Keywords
      8.5.4.2 Pragmas and Representation Clauses
      8.5.4.3 Configuration Declaration
      8.5.4.4 Partition Declaration
      8.5.4.5 Location Declaration
      8.5.4.6 Partition Attribute Main
      8.5.4.7 Pragma Starter
      8.5.4.8 Pragma Remote_Shell
      8.5.4.9 Pragma Name_Server
      8.5.4.10 Pragma Boot_Location
      8.5.4.11 Partition Attribute Self_Location
      8.5.4.12 Partition Attribute Passive
      8.5.4.13 Partition Attribute Data_Location
      8.5.4.14 Partition Attribute Allow_Light_PCS
      8.5.4.15 Pragma Priority
      8.5.4.16 Partition Attribute Priority
      8.5.4.17 Partition Attribute Host
      8.5.4.18 Pragma Import
      8.5.4.19 Partition Attribute Directory
      8.5.4.20 Partition Attribute Command_Line
      8.5.4.21 Partition Attribute Environment_Variables
      8.5.4.22 Partition Attribute Termination
      8.5.4.23 Partition Attribute Reconnection
      8.5.4.24 Pragma Version
      8.5.4.25 Partition Attribute Task_Pool
      8.5.4.26 Partition Attribute ORB_Tasking_Policy
      8.5.4.27 A Complete Example
    8.5.5 Partition Runtime Parameters
    8.5.6 Gnatdist Internals
    8.5.7 PolyORB PCS Internals
      8.5.7.1 Application Startup
      8.5.7.2 Heterogeneous System
      8.5.7.3 Allocating Partition Ids
      8.5.7.4 Executing Concurrent Remote Calls
      8.5.7.5 Priority Inheritance
      8.5.7.6 Remote Call Abortion
  8.6 Running a DSA application
9 MOMA
  9.1 What you should know before Reading this section
  9.2 Installing MOMA application personality
  9.3 Package hierarchy
10 Ada Web Server (AWS)
11 GIOP
  11.1 Installing GIOP protocol personality
  11.2 GIOP Instances
    11.2.1 IIOP
    11.2.2 SSLIOP
    11.2.3 DIOP
    11.2.4 MIOP
  11.3 Configuring the GIOP personality
    11.3.1 Common configuration parameters
    11.3.2 IIOP Configuration Parameters
    11.3.3 SSLIOP Configuration Parameters
      11.3.3.1 Ciphers name
      11.3.3.2 SSLIOP Parameters
    11.3.4 DIOP Configuration Parameters
    11.3.5 MIOP Configuration Parameters
  11.4 Code sets
    11.4.1 Supported code sets
    11.4.2 Incompatibility in code set support
    11.4.3 Adding support for new code sets
    11.4.4 Character data Converter
    11.4.5 Converters factories
    11.4.6 Registering new code sets
12 SOAP
  12.1 Installing SOAP protocol personality
  12.2 Configuring the SOAP personality
13 Tools
  13.1 `po_catref'
  13.2 `po_dumpir'
  13.3 `po_names'
Appendix A Performance considerations
Appendix B Conformance to standards
  B.1 CORBA standards conformance
    B.1.1 CORBA IDL-to-Ada mapping
    B.1.2 CORBA Core
    B.1.3 CORBA Interoperability
    B.1.4 CORBA Interworking
    B.1.5 CORBA Quality Of Service
    B.1.6 CORBA COS Services
    B.1.7 CORBA Specialized services
  B.2 RT-CORBA standards conformance
  B.3 CSIv2 standards conformance
  B.4 CORBA/GIOP standards conformance
  B.5 SOAP standards conformance
Appendix C References
Appendix D GNU Free Documentation License
Index


About This Guide
****************

This guide describes the use of PolyORB, a middleware that enables the
construction of distributed Ada applications.

   It describes the features of the middleware and related APIs and
tools, and details how to use them to build Ada applications.

What This Guide Contains
========================

This guide contains the following chapters:
   * *note Introduction to PolyORB:: provides a brief description of
     middleware and PolyORB's architecture.

   * *note Installation:: details how to configure and install PolyORB
     on your system.

   * *note Overview of PolyORB personalities:: enumerates the different
     personalities, or distribution mechanisms, PolyORB provides.

   * *note Building an application with PolyORB:: presents the
     different steps to build a distributed application using PolyORB.

   * *note Tasking model in PolyORB:: details the use of tasking
     constructs within PolyORB.

   * *note CORBA:: describes PolyORB's implementation of OMG's CORBA.

   * *note RT-CORBA:: describes PolyORB's implementation of RT-CORBA,
     the real-time extensions of OMG's CORBA.

   * *note DSA:: describes PolyORB's implementation of the Ada
     Distributed Systems Annex.

   * *note MOMA:: describes PolyORB's implementation of MOMA, the
     Message Oriented Middleware for Ada.

   * *note AWS:: describes the integration of the Ada Web Server (AWS)
     framework into PolyORB.

   * *note GIOP:: describes PolyORB's implementation of GIOP, the
     protocol defined as part of CORBA.

   * *note SOAP:: describes PolyORB's implementation of SOAP.

   * *note Tools:: describes PolyORB's tools.

   * *note Conformance to standards:: discusses the conformance of the
     PolyORB's personalities to the CORBA and SOAP standards.

   * *note References:: provides a list of useful references to
     complete this documentation.

   * *note GNU Free Documentation License:: contains the text of the
     license under which this document is being distributed.

Conventions
===========

Following are examples of the typographical and graphic conventions used
in this guide:

   * `Functions', `utility program names', `standard names', and
     `classes'.

   * `Option flags'

   * `File Names', `button names', and `field names'.

   * VARIABLES.

   * _Emphasis_.

   * [optional information or parameters]

   * Examples are described by text
          and then shown this way.

Commands that are entered by the user are preceded in this manual by
the characters "`$ '" (dollar sign followed by space). If your system
uses this sequence as a prompt, then the commands will appear exactly
as you see them in the manual. If your system uses some other prompt,
then the command will appear with the `$' replaced by whatever prompt
you are using.

   Full file names are shown with the "`/'" character as the directory
separator; e.g., `parent-dir/subdir/myfile.adb'.  If you are using GNAT
on a Windows platform, please note that the "`\'" character should be
used instead.

1 Introduction to PolyORB
*************************

1.1 Introduction to distributed systems
=======================================

A distributed system architecture comprises a network of computers and
the software components that execute on those computers. Such
architectures are commonly used to improve the performance,
reliability, and reusability of complex applications. Typically, there
is no shared address space available to remotely-located components
(that is to say, components running on different nodes of the network),
and therefore these components must communicate using some form of
message-passing.

1.1.1 Using OS Network Services
-------------------------------

There are several programming techniques for developing distributed
applications. These applications have traditionally been developed
using network programming interfaces such as sockets. Programmers have
to perform explicit calls to operating system services, a task that can
be tedious and error-prone. This includes initializing socket
connections and determining peer location, marshalling and unmarshalling
data structures, sending and receiving messages, debugging and testing
several programs at the same time, and porting the application to
several platforms to uncover subtle differences between various network
interfaces.

   Of course, this communication code can be encapsulated in wrappers
to reduce its complexity, but it is clear that most of it can be
automatically generated. Message passing diverts developer's attention
from the application domain. The query and reply scenario is a
classical scheme in distributed applications; using message passing for
such a scheme can be compared to only using the "goto" mechanism in a
non-distributed application.  This is considered unacceptable
methodology in modern software engineering. A cleaner and more
structured approach consists in using subprograms.

   In some respects, network programming can be compared to parallel
programming.  The user can decide to split his code into several pieces
and to multiplex the execution of threads himself, using a table-driven
model. The scheduling code ends up embedded in the user code. This
solution is error-prone and fragile in regard to any future
modification. Relying on an implementation of threads such as provided
in a POSIX operating environment is a better solution. Relying on
language primitives that support concurrency, such as Ada tasks, is
best, as the underlying parallelism support is thus entirely abstracted.

1.1.2 Using a Middleware Environment
------------------------------------

A middleware environment is intended to provide high level abstractions
in order to easily develop user applications.  Environments like CORBA
or Distributed Computing Environment (DCE) provide a framework to
develop client/server applications based on the Remote Procedure Call
model (RPC). The RPC model is inspired by the query and reply scheme.
In rough analogy to a regular procedure call, arguments are pushed onto
a stream, along with some data specifying the remote procedure to be
executed. The stream is transmitted over the network to the server. The
server decodes the stream, performs the regular subprogram call
locally, and then puts the output parameters into another stream, along
with the exception (if any) raised by the subprogram execution. The
server then sends this stream back to the caller. The caller decodes
the stream and raises the exception locally if needed.

   CORBA provides the same enhancements to the remote procedure model
that object-oriented languages provide to classical procedural
languages.  These enhancements include encapsulation, inheritance, type
checking, and exceptions. These features are offered through an
Interface Definition Language (IDL).

   The middleware communication framework provides all the machinery to
perform, somewhat transparently, remote procedure calls or remote object
method invocations. For instance, each CORBA interface communicates
through an Object Request Broker (ORB). A communication subsystem such
as an ORB is intended to allow applications to use objects without being
aware of their underlying message-passing implementation. In addition.
the user may also require a number of more complex services to develop
his distributed application. Some of these services are indispensable,
for example a location service that allows clients to reference remote
services via high level names (as opposed to a low level addressing
scheme involving transport-specific endpoint addresses such as IP
addresses and port numbers).  Other services provide domain-independent
interfaces that are frequently used by distributed applications.

   If we return to the multi-threaded programming comparison, the
middleware solution is close to what a POSIX library or a language like
Esterel(1) would provide for developing concurrent applications. A
middleware framework like DCE is close to a POSIX library in terms of
abstraction levels. Functionalities are very low-level and very
complex. CORBA is closer to Esterel in terms of development process.
The control part of the application can be specified in a description
language. The developer then has to fill in automatically generated
source code templates (stubs and skeletons) to build the computational
part of the application. The distribution is a pre-compilation process
and the distributed boundaries are always explicit. Using CORBA, the
distributed part is written in IDL and the core of the application is
written in a host language such as C++.

   ---------- Footnotes ----------

   (1) Esterel is an imperative synchronous language designed for the
specification and the development of reactive systems.

1.1.3 Using a Distributed Language
----------------------------------

Rather than defining a new language like the CORBA IDL, an alternative
is to extend an existing programming language with distributed
features. The distributed object paradigm provides a more
object-oriented approach to programming distributed systems. The notion
of a distributed object is an extension to the abstract data type that
allows the services provided in the type interface to be called
independently of where the actual service is executed. When combined
with object-oriented features such as inheritance and polymorphism,
distributed objects offer a more dynamic and structured computational
environment for distributed applications.

   The Distributed Systems Annex (DSA) of Ada defines several
extensions that allow the user to write a distributed system entirely in
Ada.  The types of distributed objects, the services they provide, and
the bodies of the remote methods to be executed are all defined in
conventional Ada packages. The Ada model is analogous to the Java/RMI
model.  In both languages, the IDL is replaced by well-defined language
constructs.  Therefore, the language supports both remote procedure
calls and remote object method invocations transparently, and the
semantics of distribution are consistent with the rest of the language.

   A program written in such a language is intended to communicate with
a program written in the same language, but this apparent restriction
has several useful consequences. The language can provide more powerful
features because it is not constrained by the common features available
in all host languages. In Ada, the user will define a specification of
remote services and implement them exactly as he would for ordinary,
non-distributed services. His Ada environment will compile them to
produce a stub file (on the caller side) and a skeleton file that
automatically includes the body of the services (on the receiver side).
Creating objects, obtaining or registering object references or
adapting the object skeleton to the user object implementation are made
transparent because the language environment has a full control over the
development process.

   Comparing with multi-threaded programming once again, the language
extension solution is equivalent to the solution adopted for tasking
facilities in Ada.  Writing a distributed application is as simple as
writing a concurrent application: there is no binding consideration and
no code to wrap.  The language and its run-time system take care of
most issues that would divert the programmer's attention from the
application domain.

1.2 Distribution models and middleware standards
================================================

Middleware provides a framework that hides the complex issues of
distribution, and offers the programmer high-level abstractions that
allow easy and transparent construction of distributed applications.  A
number of different standards exist for creating object-oriented
distributed applications. These standards define two subsystems that
enable interaction between application partitions:

   * the API seen by the developer's applicative objects;

   * the protocol used by the middleware environment to interact with
     other nodes in the distributed application.


Middleware implementations also offer programming guidelines and
development tools to ease the construction of large heterogeneous
distributed systems. Many issues typical to distributed programming may
still arise: application architectural choice, configuration or
deployment. Since there is no "one size fits all" architecture,
choosing the adequate distribution middleware in its most appropriate
configuration is a key design point that dramatically impacts the
design and performance of an application.

   Consequently, applications need to rapidly tailor middleware to the
specific distribution model they require. A distribution model is
defined by the combination of distribution mechanisms made available to
the application. Common examples of such mechanisms are Remote
Procedure Call (RPC), Distributed Objects or Message Passing. A
distribution infrastructure or middleware refers to software that
supports one distribution model (or several), e.g.: OMG CORBA, Java
Remote Method Invocation (RMI), the Distributed Systems Annex of Ada,
Java Message Service (MOM).

1.3 The PolyORB generic middleware
==================================

Typical middleware implementations for one platform support only one
set of such interfaces, predefined configuration capabilities and
cannot interoperate with other platforms. In addition to traditional
middleware implementations, PolyORB provides an original architecture
to enable support for multiple interoperating distribution models in a
uniform canvas.

   PolyORB is a polymorphic, reusable infrastructure for building or
prototyping new middleware adapted to specific application needs. It
provides a set of components on top of which various instances can be
elaborated. These instances (or personalities) are views on PolyORB
facilities that are compliant to existing standards, either at the API
level (application personality) or at the protocol level (protocol
personality). These personalities are mutually exclusive views of the
same architecture.

   The decoupling of application and protocol personalities, and the
support for multiple simultaneous personalities within the same running
middleware, are key features required for the construction of
interoperable distributed applications. This allows PolyORB to
communicate with middleware that implements different distribution
standards: PolyORB provides middleware-to-middleware interoperability
(M2M).

   PolyORB's modularity allows for easy extension and replacement of its
core and personality components, in order to meet specific requirements.
In this way, standard or application-specific personalities can be
created in a streamlined process, from early stage prototyping to
full-featured implementation. The PolyORB architecture also allows the
automatic, just-in-time creation of proxies between incompatible
environments.

   You may find additional technical literature on PolyORB, including
research papers and implementation notes, on the project websites:
`http://libre.adacore.com/libre/tools/polyorb/' and
`http://polyorb.objectweb.org/'.

   Note: PolyORB is the project formerly known as DROOPI, a Distributed
Reusable Object-Oriented Polymorphic Infrastructure

2 Installation
**************

2.1 Supported Platforms
=======================

PolyORB has been compiled and successfully tested on the following
platforms:

   * AIX

   * FreeBSD

   * HP-UX

   * Linux

   * MacOS X

   * Solaris

   * Tru64

   * VxWorks

   * Windows

_Note: PolyORB should compile and run on every target for which GNAT
and the `GNAT.Sockets' package are available._

2.2 Build requirements
======================

GNU tar is required to unpack PolyORB source packages.

   Ada compiler:
   * GNAT Pro 6.2.* or later

   * GNAT GPL 2009 or later

   * FSF GCC 4.4 or later

   For builds for cross targets, both a native and a cross compiler are
required, as some tools (like an IDL-to-Ada compiler) are meant for use
on the build host.

   A Python interpreter is required for installation.

   Optional:

   * (Only for older versions of GNAT, and only if you want to build
     the CORBA application personality): A C++ compiler. The OMG IDL
     specification mandates that IDL source files be preprocessed
     according   to standard C++ preprocessing rules. Newer versions of
     GNAT provide an   integrated IDL preprocessor. This feature is
     detected and used   automatically. However, for older versions of
     GNAT, PolyORB relies on   an external preprocessor provided by a
     suitable C++ compiler. Please   refer to the documentation of your
     particular version of GNAT to know   if it supports this feature.

   * XML/Ada (`http://libre.adacore.com/libre/tools/xmlada/') if you
     want to build the SOAP protocol personality.

Note: per construction, the macro `configure' used to find your GNAT
compiler looks first for the executable `gnatgcc', then `adagcc' and
finally `gcc' to find out which Ada compiler to use. You should be very
careful with your path and executables if you have multiple GNAT
versions installed. See the explanation below on the ADA environment
variable if you need to override the default guess.

2.3 Build instructions
======================

To compile and install PolyORB, execute:

       $ ./configure [some options]
       $ make
       $ make install

This will install files in standard locations.  If you want to choose a
prefix other than `/usr/local', give configure a
`--prefix=whereveryouwant' argument.

   NOTE: you must use GNU make (version 3.80 or later) to build PolyORB.

2.4 Additional instructions for cross platforms
===============================================

The `RANLIB' environment variable must be set to the path of the cross
`ranlib' prior to running `configure' with the appropriate `--target'
option.

   For example, for VxWorks 5 execute:
       $ export RANLIB=ranlibppc
       $ ./configure --target=powerpc-wrs-vxworks [some options]
       $ make
       $ make install

   Only one PolyORB installation (native or cross) is currently possible
with a given `--prefix'. If both a native and a cross installation are
needed on the same machine, distinct prefixes must be used.

   Use `./configure --help' for a full list of available configuration
switches.

2.5 Building the documentation and PolyORB's examples
=====================================================

PolyORB's documentation and examples are built separately.

   To build the examples, run `make examples' in the root directory.
The build process will only build examples that correspond to the
personalities you configured. Note that some examples require the CORBA
COS Naming and IR services to be enabled (using
`--enable-corba-services="naming ir"' on the `configure' command line).

   Similarly, to build the documentation, run `make docs'.

   You may install PolyORB's documentation in a standard location using
`make install'.

2.6 Build Options
=================

Available options for the 'configure' script include:

   * `--with-appli-perso="..."': application personalities to build

     Available personalities: AWS, CORBA, DSA, MOMA

     e.g.   `--with-appli-perso="corba moma"' to build both the CORBA
               and MOMA personalities

   * `--with-proto-perso="..."': protocol personalities to build

     Available personalities: GIOP, SOAP

     e.g.   `--with-proto-perso="giop soap"' to build both the GIOP
             and SOAP personalities

   * `--with-idl-compiler="..."': select IDL compiler

     Available IDL compilers: iac (default), idlac

     e.g.  `--with-idl-compiler=''iac''' to build iac

   * `--with-corba-services="..."': CORBA COS services to build

     Available services: event, ir, naming, notification, time

     e.g.  `--with-corba-services="event naming"' to build only
     COS Event and COS Naming.


By default, only the CORBA and GIOP personalities are built, and no
CORBA Services are built.

   * `--with-openssl': build SSL support and SSL dependent features,
     including the IIOP/SSLIOP personality

   * `--help': list all options available

   * `--enable-shared': build shared libraries.

   * `--enable-debug':  enable debugging information generation and
     supplementary runtime checks. Note that this option has a
     significant space and time cost, and is not recommended for
     production use.


2.7 Compiler, Tools and Run-Time libraries Options
==================================================

The following environment variables can be used to override configure's
guess at what compilers to use:

   * `CC':  the C compiler

   * `ADA': the Ada compiler (e.g. gcc, gnatgcc or adagcc)

   * `CXXCPP', `CXXCPPFLAGS': the preprocessor used by the IDL-to-Ada
     compiler (only when setting up the CORBA application personality).
     CORBA specifications require this preprocessor to be compatible
     with the preprocessing rules defined in the C++ programming
     language specifications.


For example, if you have two versions of GNAT installed and available
in your `PATH', and configure picks the wrong one, you can indicate
what compiler should be used with the following (assuming Bourne shell
syntax):

       $ ADA=/path/to/good/compiler/gcc ./configure [options]

   PolyORB will be compiled with GNAT build host's configuration,
including run-time library. You may override this setting using
`ADA_INCLUDE_PATH' and `ADA_OBJECTS_PATH' environment variables. See
GNAT User's Guide for more details.

   You can add specific build options to GNAT using the
`EXTRA_GNATMAKE_FLAGS' variable:

       $ EXTRA_GNATMAKE_FLAGS=--RTS=rts-sjlj ./configure [options]

   You can also pass compiler-only flags using the `ADAFLAGS' variable.

   NOTE: Developers building PolyORB from the version control repository
will need to rebuild the configure script and other files. To do so,
from the top-level source directory, run the support/reconfig script
after each update from the repository. In addition to the requirements
above, developers will need autoconf 2.57 or newer, automake 1.6.3 or
newer, and libtool 1.5.8 or newer.

2.8 Platform notes
==================

Solaris (all versions):

   /usr/ucb/tr is not suitable to build PolyORB. Your PATH must be set
to that tr(1) is /usr/bin/tr, /use/xpg4/bin/tr or GNU tr.

Tru64 5.1A:

   The default maximal data segment size may not be sufficient to
compile PolyORB. If a GNAT heap exhausted error message occurs during
build, try raising this limit using:
     ulimit -d unlimited

AIX 5.2:

   PolyORB must be compiled with the -mminimal-toc compiler switch.
This is taken care of automatically by the PolyORB configure script.

   The 'ulimit' command may be needed as for Tru64 (see above).

HP-UX 11.00:

   The version of install(1) from /opt/imake/bin on HP-UX is not
suitable for installing PolyORB. Make sure that /opt/imake/bin is not
on the PATH when building and installing PolyORB.

3 Overview of PolyORB personalities
***********************************

A personality is an instantiation of specific PolyORB components. It
provides the mechanisms specified by a distribution model, e.g. an API,
a code generator or a protocol stack.

   This section provides a brief overview of existing personalities.

   _Note: some of these personalities are available only through
PolyORB's repository._

3.1 Application personalities
=============================

Application personalities constitute the adaptation layer between
application components and middleware. They provide APIs and/or a code
generator to register application entities with PolyORB's core, and
interoperate with the core to allow the exchange of requests with
remote entities.

3.1.1 CORBA
-----------

CORBA is the OMG specification of a Distributed Object Computing (DOC)
distribution model (`[OMG04]'). It is now a well-known and
well-established specification, used in a wide range of industrial
applications.

   PolyORB provides a CORBA-compatible implementation based on a
mapping of the IDL language version 1.2 described in `[OMG01]' and CORBA
core specifications. PolyORB also provides an implementation of various
additional specifications described by the OMG, including `COS
Services: COS Naming, Notification, Event, Time', and additional
specifications: `RT-CORBA', `PortableInterceptors', `DynamicAny'.

3.1.2 Distributed Systems Annex of Ada (DSA)
--------------------------------------------

The Distributed Systems Annex of Ada (DSA) `[ISO06]' is a normative
part of the language specification. It was first introduced in the "Ada
95" revision of the language (`[ISO95]'). It describes remote
invocation schemes applied to most language constructs.

3.1.3 Message Oriented Middleware for Ada (MOMA)
------------------------------------------------

MOMA (Message Oriented Middleware for Ada) provides message passing
mechanisms. It is an Ada adaptation of Sun's Java Message Service (JMS)
`[SUN99]', a standardized API for common message passing models.

3.1.4 Ada Web Server (AWS)
--------------------------

The Web Server personality provides the same API as the Ada Web Server
project (AWS) `[Obr03]'. It allows for the implementation of web
services, web server applications, or classical web pages. AWS-based
servers allow the programmer to directly interact with incoming or
outgoing `HTTP' and `SOAP' requests.

3.2 Protocol personalities
==========================

Protocol personalities handle the mapping of requests (representing
interactions between application entities) onto messages exchanged
through a communication network, according to a specific protocol.

3.2.1 GIOP
----------

GIOP is the transport layer of the CORBA specifications. GIOP is a
generic protocol. This personality implements GIOP versions from 1.0 to
1.2 along with the CDR representation scheme to map data types between
the neutral core layer and CDR streams. It also provides the following
dedicated instances:

   * IIOP supports synchronous request semantics over TCP/IP, 

   * IIOP/SSIOP supports synchronous request semantics using SSL
     sockets, 

   * MIOP instantiation of GIOP enables group communication over IP
     multicast, 

   * DIOP relies on UDP/IP communications to transmit one-way requests
     only.  


3.2.2 SOAP
----------

The SOAP protocol `[W3C03]' enables the exchange of structured and
typed information between peers. It is a self-describing XML document
`[W3C03]' that defines both its data and semantics. Basically, SOAP
with `HTTP' bindings is used as a communication protocol for Web
Services.

4 Building an application with PolyORB
**************************************

4.1 Compile-time configuration
==============================

The user may configure some elements of a PolyORB application at
compile-time.

4.1.1 Tasking runtimes
----------------------

PolyORB provides several tasking runtimes. The user may select the most
appropriate one, depending on application requirements. The tasking
runtimes determine the constructs PolyORB may use for its internal
synchronizations.

   * `No_Tasking': There is no dependency on the Ada tasking runtime,
     middleware is mono-task.

   * `Full_Tasking': Middleware uses Ada tasking constructs, middleware
     can be configured for multi-tasking.

   * `Ravenscar' : Middleware uses Ada tasking constructs, with the
     limitations of the Ravenscar profile `[DB98]'.  Middleware can be
     configured for multi-tasking.  

See *note Tasking model in PolyORB:: for more information on this point.

4.1.2 Middleware tasking policies
---------------------------------

PolyORB provides several tasking policies. A tasking policy defines how
tasks are used by the middleware to process incoming requests.

   * `No_Tasking': There is only one task in middleware, processing all
     requests.

   * `Thread_Per_Session': One task monitors communication entities.
     One task is spawned for each active connection. This task handles
     all incoming requests on this connection.

   * `Thread_Per_Request': One task monitors communication entities.
     One task is spawned for each incoming request.

   * `Thread_Pool': A set of tasks cooperate to handle all incoming
     requests.


See *note Tasking model in PolyORB:: for more information on this point.

4.1.3 Sample files
------------------

PolyORB provides a set of predefined setup packages. You must `with'
one of them in your application node to activate the corresponding
setup.

   * `PolyORB.Setup.No_Tasking_Client': a client node, without any
     tasking support, configured to use all protocol personalities
     built with PolyORB. Note that this configuration should not be
     used with multiple application tasks.

   * `PolyORB.Setup.Thread_Pool_Client': a client node, with tasking
     enabled, configured to use all protocol personalities built with
     PolyORB.  This configuration places no restriction on the use of
     tasking by application code. Middleware tasking policy is
     `Thread_Pool'.

   * `PolyORB.Setup.Ravenscar_TP_Server': a server node, with tasking
     enabled, configured to use all protocol personalities built with
     PolyORB. Middleware tasking runtime follows Ravenscar's profile
     restrictions. Middleware tasking policy is `Thread_Pool'.

   * `PolyORB.Setup.Thread_Per_Request_Server': a server node, with
     tasking enabled, configured to use all protocol personalities
     built with PolyORB. Middleware tasking policy is
     `Thread_Per_Request'.

   * `PolyORB.Setup.Thread_Per_Session_Server': a server node, with
     tasking enabled, configured to use all protocol personalities
     built with PolyORB. Middleware tasking policy is
     `Thread_Per_Session'.

   * `PolyORB.Setup.Thread_Pool_Server': a server node, with tasking
     enabled, configured to use all protocol personalities built with
     PolyORB. Middleware tasking policy is `Thread_Pool'.


To use one of these configurations, add a dependency on one of these
packages, for example, `with PolyORB.Setup.Thread_Pool_Server;'. The
elaboration of the application (based on Ada rules) and the
initialization of the partition (based on the application personalities
mechanisms) will properly set up your application.

4.2 Run-time configuration
==========================

The user may configure some elements of a PolyORB application at run
time.

   Using the default configurations provided by PolyORB, the parameters
are read in the following order: command line, environment variables,
configuration file. PolyORB will use the first value that matches the
searched parameter.

4.2.1 Using a configuration file
--------------------------------

A configuration file may be used to configure a PolyORB node. A sample
configuration file may be found in `src/polyorb.conf'.

   The syntax of the configuration file is:
   * empty lines and lines that have a '#' in column 1 are ignored;

   * sections can be started by lines of the form     `[ SECTION-NAME
     ]';

   * variable assignments can be performed by lines of the form
     `VARIABLE-NAME = VALUE'.

     Any variable assignment is local to a section.

     Assignments that occur before the first section declaration are
     relative to section [environment].  Section and variable names are
     case sensitive.

     Furthermore, each time a value starts with `"file:"', the contents
     of the file are used instead.

Default search path for `polyorb.conf' is current directory.
Environment variable `POLYORB_CONF' may be used to set up information
on configuration file.

   PolyORB's configuration file allows the user to
  1. enable/disable the output of debug information

  2. set up default reference on naming service

  3. select the default protocol personality

  4. set up each protocol personality

The configuration file is read once when running a node, during
initialization. Look in the sample configuration file
`src/polyorb.conf' to see the available sections and variables.

4.2.2 Using environment variables
---------------------------------

A variable `Var.Iable' in section `[Sec]' can be overridden by setting
environment variable `"POLYORB_SEC_VAR_IABLE"'.

4.2.3 Using the command line
----------------------------

PolyORB allows to set up configuration variables on the command line.
The syntax is close to the one described in configuration files.  A
variable `Var.Iable' in section `[Sec]' can be overridden with flag
`--polyorb-<sec>-<var>-<iable>[=<value>]'.

4.2.4 Using a source file
-------------------------

Many embedded systems do not have a filesystem or a shell, so the
previous run-time configuration methods cannot be used on these targets.
On these platforms, a PolyORB node can also be configured using the API
of package `PolyORB.Parameters.Static'. An example configuration file
may be found in `examples/static/po_static_conf.ads'.

   An array of PolyORB parameters of type `Static_Parameters_Array' is
first declared containing a list of pairs of Variable and Value strings.
The syntax is close to the one described in configuration files.  A
variable `Var.Iable' in section `[Sec]' is specified as the pair of
strings `"[sec]var.iable", "<value>"'.

   There is no need to with this `po_static_conf.ads' in the application
source code, the only requirement is that the array is exported with the
external name "`__polyorbconf_optional'". This allows to modify PolyORB
parameters without recompiling the application, just relinking it. For
example:

       $ gnatmake -c po_static_conf.ads `polyorb-config`
       $ gnatmake -b -l server.adb `polyorb-config` -largs po_static_conf.o

   Note the `-l' flag to gnatmake for linking only, and the need to
specify to the linker the object file with the array using `-largs' if
no package withs it.

   It should be noticed that this static array of parameters is read at
elaboration time only, this API cannot be used to modify the PolyORB
configuration at run-time.

4.3 Setting up protocol personalities
=====================================

PolyORB allows the user to activate some of the available protocol
personalities and to set up the preferred protocol. Protocol-specific
parameters are defined in their respective sections.

4.3.1 Activating/Deactivating protocol personalities
----------------------------------------------------

Protocol activation is controlled by PolyORB's configuration file.

   The section `[access_points]' controls the initialization of _access
points_. An access point is a node entry point that may serve incoming
requests.

     [access_points]
     soap=enable
     iiop=enable
     diop=disable
     uipmc=disable

This example activates SOAP and IIOP, but deactivates DIOP and MIOP.

   The section `[modules]' controls the activation/deactivation of some
modules within PolyORB. It is used to enable _bindings_ to remote
entities.

     [modules]
     binding_data.soap=enable
     binding_data.iiop=enable
     binding_data.diop=disable
     binding_data.uipmc=disable

This example enables the creation of bindings to remote objects using
SOAP or IIOP. Objects cannot be reached using DIOP or UIPMC.

   _Note: by default, all configured personalities are activated._

4.3.2 Configuring protocol personality preferences
--------------------------------------------------

The user may affect a _preference_ to each protocol personality. The
protocol with the higher preference will be selected among possible
protocols to send a request to a remote node.

   See `polyorb.binding_data.<protocol>.preference' in section
`[protocol]' to set up protocol's preference.

   Possible protocols are defined as the protocols available on the
remote node, as advertised in its _object reference_.  `IOR' or
`corbaloc' references may support multiple protocols; `URI' references
support only one protocol.

   Each protocol supports a variety of configuration parameters, please
refer to the protocols' sections for more details.

4.4 Activating debugging traces
===============================

To activate the output of debug information, you must first configure
and compile PolyORB with debugging traces activated (which is the
default, unless your build is configured with
`--enable-debug-policy=ignore').

   To output debugging traces on a selected package, create a
configuration file with a `[log]' section and the name of the packages
for which you want debug information:

     # Sample configuration file, output debug for PolyORB.A_Package
     [log]
     polyorb.a_package=debug

   Note that some packages may not provide such information. See the
sample configuration file `src/polyorb.conf' for the complete list of
packages that provide traces.

   A default logging level may be specified using a line of the form
     default=<level>

   Time stamps may optionally be prepended to every generated trace.
This is enabled using:
     timestamp=true

4.5 Tracing exceptions
======================

To trace exception propagation in PolyORB's source code, activate
debugging traces for package `PolyORB.Exceptions'.

4.6 `polyorb.gpr'
=================

This section describes how to build your program using project files.
An alternative method, using `polyorb-config', is described in the
following section. `polyorb-config' is intended primarily for Unix-like
systems. The project-file method will work on all supported systems.

   To build your application, create a project file as usual.  Import
the `polyorb.gpr' project by putting `with "polyorb";' in your project
file.

   Set the ADA_PROJECT_PATH environment variable to point to the
directory containing `polyorb.gpr', which is `<prefix>/lib/gnat'.  If
SOAP is being used, ADA_PROJECT_PATH must also be set so we can find
`xmlada.gpr'.

   If your project file is `my_proj.gpr', you can build it by saying:

       $ gnatmake -P my_proj

   See the GNAT User's Guide and the GNAT Reference Manual for more
information on project files.

4.7 `polyorb-config'
====================

`polyorb-config' returns path and library information on PolyORB's
installation.  It can be used on the `gnatmake' command line, like this:

       $ gnatmake my_program.adb `polyorb-config`



     NAME
            polyorb-config  - script to get information about the installed version
            of PolyORB.

     SYNOPSIS
            polyorb-config [--prefix[=DIR]] [--exec-prefix[=DIR]] [--version|-v]
            [--config] [--libs] [--cflags] [--idls] [--help]

     DESCRIPTION
            polyorb-config  is  a  tool  that is used to determine the compiler and
            linker flags that should be used to compile and link programs that  use
            PolyORB.

     OPTIONS
            polyorb-config accepts the following options:

            --prefix[=DIR]
                     Output the directory in which PolyORB architecture-independent
                    files are installed, or set this directory to DIR.

            --exec-prefix[=DIR]
                     Output the directory in which  PolyORB  architecture-dependent
                    files are installed, or set this directory to DIR.

            --version
                    Print  the  currently installed version of PolyORB on the stan-
                    dard output.

            --config
                    Print the configuration of the currently installed  version  of
                    PolyORB on the standard output.

            --libs  Print  the  linker  flags  that are necessary to link a PolyORB
                    program.

            --cflags
                    Print the compiler flags that are necessary to compile a  Poly-
                    ORB program.

            --idls
                    Output flags to set up path to CORBA's IDL for idlac.

            --with-appli-perso=P,P,P
                    Restrict output to only those flags relevant to the listed
                    applicative personalities.

            --with-proto-perso=P,P,P
                    Restrict output to only those flags relevant to the listed
                    protocol personalities.

            --with-corba-services=S,S,S
                   Restrict output to only those flags relevant to the listed
                   services.

            --help  Print help message.

5 Tasking model in PolyORB
**************************

5.1 PolyORB Tasking runtimes
============================

PolyORB may use any of three different tasking runtimes to manage and
synchronize tasks, if any. Tasking runtime capabilities are defined in
the Ada Reference Manual `[ISO06]'.

   The choice of a specific tasking runtime is a compile-time parameter,
*note Tasking runtimes:: for more details on their configuration.

5.1.1 Full tasking runtime
--------------------------

Full tasking runtime refers to the configuration in which there are
dependencies on the tasking constructs defined in chapter 9 of
`[ISO06]'. It makes use of all capabilities defined in this section to
manage and synchronize tasks.

   In this configuration, a PolyORB application must be compiled and
linked with a tasking-capable Ada runtime.

5.1.2 No tasking runtime
------------------------

No tasking runtime refers to the configuration in which there is no
dependency on tasking constructs. Thus, no tasking is required.

   In this configuration, a PolyORB application may be compiled and
linked with a tasking-capable Ada runtime or a no-tasking Ada runtime.

5.1.3 Ravenscar tasking runtime
-------------------------------

Ravenscar tasking runtime refers to the configuration in which tasking
constructs are compliant with the _Ravenscar tasking restricted
profile_.

   In this configuration, a PolyORB application may be compiled and
linked with a tasking-capable Ada runtime or a Ravenscar Ada runtime.

   To configure tasking constructs used by PolyORB, one must instantiate
the `PolyORB.Setup.Tasking.Ravenscar' generic package shown below to
set up tasks and protected objects used by PolyORB core.


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --      P O L Y O R B . S E T U P . T A S K I N G . R A V E N S C A R       --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- As a special exception under Section 7 of GPL version 3, you are granted --
     -- additional permissions described in the GCC Runtime Library Exception,   --
     -- version 3.1, as published by the Free Software Foundation.               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     --  You should instantiate this package to set up a ravenscar profile.

     with System;

     with PolyORB.Tasking.Profiles.Ravenscar.Threads.Annotations;

     with PolyORB.Tasking.Profiles.Ravenscar.Threads;
     with PolyORB.Tasking.Profiles.Ravenscar.Mutexes;
     with PolyORB.Tasking.Profiles.Ravenscar.Condition_Variables;

     generic
        Number_Of_Application_Tasks    : Integer;
        --  Number of tasks created by the user.

        Number_Of_System_Tasks         : Integer;
        --  Number of tasks created by the PolyORB run-time library.

        Number_Of_Conditions           : Integer;
        --  Number of preallocated conditions.

        Number_Of_Mutexes              : Integer;
        --  Number of preallocated mutexes.

        Task_Priority                  : System.Priority;
        --  Priority of the tasks of the pool.

        Storage_Size                   : Natural;
        --  Stack size of the system tasks.

     package PolyORB.Setup.Tasking.Ravenscar is

        package Threads_Package is
           new PolyORB.Tasking.Profiles.Ravenscar.Threads
          (Number_Of_Application_Tasks,
           Number_Of_System_Tasks,
           Task_Priority,
           Storage_Size);

        package Thread_Annotations_Package is new Threads_Package.Annotations;

        package Conditions_Package is
           new PolyORB.Tasking.Profiles.Ravenscar.Condition_Variables
          (Threads_Package,
           Number_Of_Conditions);

        package Mutexes_Package is
           new PolyORB.Tasking.Profiles.Ravenscar.Mutexes
          (Threads_Package,
           Number_Of_Mutexes);

     end PolyORB.Setup.Tasking.Ravenscar;

5.2 PolyORB ORB Tasking policies
================================

PolyORB ORB Tasking policies control the creation of tasks to process
all middleware internal jobs, e.g. request processing, I/O monitoring.

Note: there is a dependency between ORB Tasking policies, and the
runtime used, as detailed below.

5.2.1 No Tasking
----------------

Under the No Tasking ORB policy, no tasks are created within the
middleware instance: it uses the environment task to process all jobs.
Note that this policy is not thread safe and is compatible with the No
tasking runtime only.

5.2.2 Thread Pool
-----------------

Under the Thread Pool ORB policy, the middleware creates a pool of
threads during initialization of PolyORB. This pool processes all jobs.
The number of tasks in the thread pool can be configured by three
parameters in the `[tasking]' configuration section.

   * `min_spare_threads' indicates the number of tasks created at
     startup.

   * `max_spare_threads' is a ceiling. When a remote subprogram call is
     completed, its anonymous task is deallocated if the number of
     unused tasks already in the pool is greater than the ceiling. If
     not, then the task is queued in the pool.

   * `max_threads' indicates the maximum number of tasks in the pool.


   *Note PolyORB Tasking configuration::, for more information on how to
configure the number of tasks in the thread pool.

5.2.3 Thread Per Session
------------------------

Under the Thread Per Session ORB policy, the middleware creates one
task when a new session (one active connection) is opened. The task
terminates when the session is closed.

5.2.4 Thread Per Request
------------------------

Under the Thread Per Request ORB policy, the middleware creates one
task per incoming request. The task terminates when the request is
completed.

5.3 PolyORB Tasking configuration
=================================

The following parameters allow the user to set up some of the tasking
parameters.


     ###############################################################################
     # Parameters for tasking
     #

     [tasking]
     # Default storage size for all threads spawned by PolyORB
     #storage_size=262144

     # Number of threads by Thread Pool tasking policy
     #min_spare_threads=4
     #max_spare_threads=4
     #max_threads=4

5.4 PolyORB ORB Controller policies
===================================

The PolyORB ORB Controller policies are responsible for the management
of the global state of the middleware: they assign middleware internal
jobs, or I/Os monitoring to middleware tasks.

   ORB Controller policies grant access to middleware internals and
affect one action for each middleware task. They ensure that all tasks
work concurrently in a thread-safe manner.

5.4.1 No Tasking
----------------

The No Tasking ORB Controller policy is dedicated to no-tasking
middleware configurations; the middleware task executes the following
loop: process internal jobs, then monitor I/Os.

5.4.2 Workers
-------------

The Workers ORB Controller policy is a simple controller policy: all
tasks are equal, they may alternatively and randomly process requests
or wait for I/O sources.

   Note: this is the default configuration provided by PolyORB sample
setup files, *Note Sample files::.

5.4.3 Half Sync/Half Async
--------------------------

The Half Sync/Half Async ORB Controller policy implements the "Half
Sync/Half Async" design pattern: it discriminates between one thread
dedicated to I/O monitoring that queue middleware jobs; another pool of
threads dequeue jobs and process them.

   Note: this pattern is well-suited to process computation-intensive
requests.

5.4.4 Leader/Followers
----------------------

The Leader/Followers ORB Controller policy implements the
"Leader/Followers " design pattern: multiple tasks take turns to
monitor I/O sources and then process requests that occur on the event
sources.

   Note: this pattern is adapted to process a lot of light requests.

5.5 PolyORB ORB Controller configuration
========================================

The following parameters allow the user to set up parameters for ORB
Controllers.


     ###############################################################################
     # Parameters for ORB Controllers
     #

     [orb_controller]
     # Interval between two polling actions on one monitor
     #polyorb.orb_controller.polling_interval=0

     # Timeout when polling on one monitor
     #polyorb.orb_controller.polling_timeout=0

6 CORBA
*******

6.1 What you should know before Reading this section
====================================================

This section assumes that the reader is familiar with the CORBA
specifications described in `[OMG04]' and the _IDL-to-Ada_ mapping
defined in `[OMG01]'.

6.2 Installing CORBA application personality
============================================

Ensure PolyORB has been configured and then compiled with the CORBA
application personality. See *note Building an application with
PolyORB:: for more details on how to check installed personalities.

   To build the CORBA application personality, *note Installation::.

6.3 IDL-to-Ada compiler
=======================

PolyORB provides two IDL-to-Ada compilers:

  1. `iac' is the new, optimized PolyORB IDL-to-Ada compiler.

  2. `idlac' is the legacy PolyORB IDL-to-Ada compiler,

6.3.1 Usage of `iac'
--------------------

`iac' is PolyORB's new IDL-to-Ada compiler. It supports many command
line parameters to control code generation optimizations such as use of
static hashing for deterministic request dispatching, and optimized
GIOP marshalling for CORBA applications.



     NAME
            iac - PolyORB's IDL-to-Ada compiler

     SYNOPSIS
            iac [options] file [-cppargs args...]

     DESCRIPTION
            iac is an IDL-to-Ada compiler, compliant with version 1.2 of the
            ``Ada Language Mapping Specification'' produced by the OMG.

     OPTIONS
            iac accepts the following options:


       -h       Print this help message, and do nothing else

       file is the name of the .idl file (.idl suffix optional)

       -E       Preprocess only
       -k       Keep temporary files
       -o DIR   Output directory (DIR must exist)
       -p       Produce source on standard output
       -q       Quiet mode

       -dm      Generate debug messages when analyzing scopes

       -df      Dump the frontend tree (the IDL tree)

       -cppargs Pass arguments to the C++ preprocessor
       -I <dir> Shortcut -cppargs -I directory. Use this flag
                for the imported entities
       -nocpp   Do not preprocess input

       -gnatW8  Use UTF-8 character encoding in Ada output.
                (Default is Latin-1.)

       -<lang>  Generate code for one of the following languages:

        types   Generate a list of all types present in the IDL file
                -p       Print the list generated

        ada     (default) Generate Ada source code
                -i       Generate implementation packages
                -c       Generate code for client side only
                -s       Generate code for server side only
                -d       Generate delegation package (defunct)
                -ir      Generate code for interface repository
                -noir    Do not generate code for interface repository (default)
                -hc      Minimize CPU time in perfect hash tables in skels
                -hm      Minimize memory use in perfect hash tables in skels
                         This is the default.
                -rs      Use the SII/SSI to handle requests
                -rd      Use the DII/DSI to handle requests (default)
                -da      Dump the Ada tree
                -db      Generate only the package bodies
                -ds      Generate only the package specs
                -dw      Output the withed entities
                -dt      Output tree warnings
                -di      Generate code for imported entities

        idl     Dump parsed IDL file
                -b n     Base to output integer literals
                         As a default (zero) use base from input
                -e       Expand IDL Tree
                -df      Dump IDL Tree (may be used in conjunction with -e
                         to dump the expanded IDL tree)
                -di      Output IDL code of imported entities  (may be
                         used in conjunction with -e to output the
                         expanded IDL code)

     EXIT STATUS
            iac returns one of the following values upon exit:

            0      Successful completion

            1      Usage error

            2      Illegal IDL specification

`iac' creates several files :

   * `myinterface.ads', `myinterface.adb' : these files contain   the
     mapping for user defined types (client and server side).

   * `myinterface-impl.ads', `myinterface-impl.adb' :   these files are
     to be filled in by the user. They contain the implementation of
     the server. They are generated only if the -i flag is specified.

   * `myinterface.ads', `myinterface.adb' : these files   contain the
     client stubs for the interface.

   * `myinterface-skel.ads', `myinterface-skel.adb' : these files
     contain the server-side skeletons for the interface.

   * `myinterface-helper.ads', `myinterface-helper.adb' : these   files
     contain subprograms to marshal data into CORBA Any containers.

   * `myinterface-ir_info.ads', `myinterface-ir_info.adb' : these
     files contain code for registering IDL definitions in the CORBA
     Interface Repository. They are generated only if the `'-ir'' flag
     is specified.

   * `myinterface-cdr.ads', `myinterface-cdr.adb' : these   files
     contain code for optimized CDR marshalling of GIOP messages. They
     are generated only if the `'-rs'' flag is specified.


6.3.2 Usage of `idlac'
----------------------

`idlac' is PolyORB's IDL-to-Ada compiler.



     NAME
            idlac - PolyORB's IDL-to-Ada compiler

     SYNOPSIS
            idlac [-Edikpqv] [-[no]ir] [-gnatW8] [-o DIR] idl_file [-cppargs ...]

     DESCRIPTION
            idlac is an IDL-to-Ada compiler, compliant with version 1.2 of the
            ``Ada Language Mapping Specification'' produced by the OMG.

     OPTIONS
            idlac accepts the following options:

            -E      Preprocess only.

            -d      Generate delegation package.

            -i      Generate implementation template.

            -s      Generate server side code.

            -c      Generate client side code.

            -k      Keep temporary files.

            -p      Produce source on standard output.

            -q      Be quiet (default).

            -v      Be verbose.

            -ir     Generate code for interface repository.

            -noir   Don't generate code for interface repository (default).

            -gnatW8
                    Use UTF8 character encoding

            -o DIR Specify output directory

            -cppargs ARGS
                    Pass ARGS to the C++ preprocessor.

            -I dir  Shortcut for -cppargs -I dir.

     EXIT STATUS
            idlac returns one of the following values upon exit:

            0      Successful completion

            1      Usage error

            2      Illegal IDL specification

`idlac' creates several files :

   * `myinterface.ads', `myinterface.adb' : these files contain   the
     mapping for user defined types (client and server side).

   * `myinterface-impl.ads', `myinterface-impl.adb' :   these files are
     to be filled in by the user. They contain the   implementation of
     the server. They are generated only if the -i flag   is specified.

   * `myinterface.ads', `myinterface.adb' : these files   contain the
     client stubs for the interface.

   * `myinterface-skel.ads', `myinterface-skel.adb' : these files
     contain the server-side skeletons for the interface.

   * `myinterface-helper.ads', `myinterface-helper.adb' : these   files
     contain subprograms to marshal data into CORBA Any containers.

   * `myinterface-ir_info.ads', `myinterface-ir_info.adb' : these
     files contain code for registering IDL definitions in the CORBA
     Interface   Repository. They are generated only if the `'-ir''
     flag is specified.


6.3.3 Difference between idlac and iac
--------------------------------------

This section lists the main differences between `idlac' and `iac'

   * `iac' is backward compatible with `idlac', but lacks the following
     feature:
       1. generation of delegation files.

   `iac' implements additional name clash resolution rules.  When the
name of an IDL operation clashes with a primitive operation of
Ada.Finalization.Controlled (of which CORBA.Object.Ref is a derived
type), it is prefixed with "IDL_" in generated sources.

6.4 Resolving names in a CORBA application
==========================================

PolyORB implements the CORBA COS Naming service.

6.4.1 `po_cos_naming'
---------------------

`po_cos_naming' is a standalone server that supports the CORBA COS
Naming specification. When launched, it returns its `IOR' and
`corbaloc', which can then be used by other CORBA applications.

   If you want `po_cos_naming' to return the same `IOR' or `corbaloc'
at each startup, you must set a default listen port for the protocol
personalities you use. See *note Configuring protocol personality
preferences:: for more details.

   `po_cos_naming' can output its `IOR' directly to a file using the
`-file <filename>' flag.  This, in conjonction with the `'file://''
naming scheme provided by `CORBA', provides a convenient way to store
initial references to the Naming Service.

     Usage: po_cos_naming
      -file <filename> : output COS Naming IOR to 'filename'
      -help : print this help
      [PolyORB command line configuration variables]

6.4.2 Registering the reference to the COS Naming server
--------------------------------------------------------

You have two ways to register the reference to the root context of the
COS Naming server the application will use:

   * Setting up the `name_service' entry in the `[corba]' section in
     your configuration file, `name_service' is the `IOR' or `corbaloc'
     of the COS Naming server to use. See *note Using a configuration
     file:: for more details.

   * Registering an initial reference using the `-ORBInitRef
     NamingService=<IOR>' or `-ORBInitRef NamingService=<corbaloc>'
     command-line argument. See the CORBA specifications for more
     details.

   * Registering an initial reference for `NamingService' using the
     `CORBA.ORB.Register_Initial_Reference' function. See the CORBA
     specifications for more details.


6.4.3 Using the COS Naming
--------------------------

PolyORB provides a helper package to manipulate the COS Naming in your
applications. See *note PolyORB specific APIs:: for more details.

6.5 The CORBA Interface Repository
==================================

PolyORB implements the CORBA Interface Repository.

6.5.1 `po_ir'
-------------

`po_ir' is a standalone server that supports the CORBA Interface
Repository. When launched, it returns its `IOR' and `corbaloc', which
can then be used by other CORBA applications.

   If you want `po_ir' to return the same `IOR' or `corbaloc' at each
startup, you must set a default listen port for the protocol
personalities you use. See *note Configuring protocol personality
preferences:: for more details.

6.5.2 Using the Interface Repository
------------------------------------

The IDL-to-Ada compiler generates a helper package that allows you to
register all entities defined in your IDL specification in the
Interface Repository.

6.6 Building a CORBA application with PolyORB
=============================================

6.6.1 `echo' example
--------------------

We consider building a simple "Echo" CORBA server and client. This
application echoes a string. The source code for this example is
located in the `examples/corba/echo' directory in the PolyORB
distribution. This applications uses only basic elements of CORBA.

   To build this application, you need the following pieces of code:

  1. IDL definition of an `echo' object

  2. Implementation code for the `echo' object

  3. Code for client and server nodes

6.6.1.1 IDL definition of an `echo' object
..........................................

This interface defines an `echo' object with a unique method
`echoString'. Per construction, this method returns its argument.


     interface Echo {
       string echoString (in string Mesg);
     };

6.6.1.2 Implementation code for the `echo' object
.................................................

Package `Echo.Impl' is an implementation of this interface. This
implementation follows the _IDL-to-Ada_ mapping.


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --                            E C H O . I M P L                             --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     with CORBA;
     with PortableServer;

     package Echo.Impl is

        --  My own implementation of echo object.
        --  This is simply used to define the operations.

        type Object is new PortableServer.Servant_Base with null record;

        type Object_Acc is access Object;

        function EchoString
          (Self : access Object;
           Mesg : CORBA.String)
          return CORBA.String;

     end Echo.Impl;


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --                            E C H O . I M P L                             --
     --                                                                          --
     --                                 B o d y                                  --
     --                                                                          --
     --         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     with Ada.Text_IO;

     with Echo.Skel;
     pragma Warnings (Off, Echo.Skel);
     --  No entity from Echo.Skel is referenced.

     package body Echo.Impl is

        ----------------
        -- EchoString --
        ----------------

        function EchoString
          (Self : access Object;
           Mesg : CORBA.String)
          return CORBA.String
        is
           pragma Warnings (Off);
           pragma Unreferenced (Self);
           pragma Warnings (On);

           S : String := CORBA.To_Standard_String (Mesg);
           L : Natural := S'Last;
        begin
           if S'Length > 13 then
              L := S'First + 12;
              S (L - 2 .. L) := (others => '.');
           end if;
           Ada.Text_IO.Put_Line
             ("Echoing string: « " & S (S'First .. L) & " »");
           return Mesg;
        end EchoString;

     end Echo.Impl;

Note: `Echo.Impl' body requires a dependency on `Echo.Skel' to ensure
the elaboration of skeleton code and the correct setup of PolyORB's
internals.

6.6.1.3 Test code for client and server nodes
.............................................

Client and server code demonstrate how to make a remote invocation on a
CORBA object, and how to set up an object on a server node.

   _Note: the dependency on `PolyORB.Setup.Client' or
`PolyORB.Setup.No_Tasking_Server' enforces compile-time configuration,
*note Sample files::._

   * Client code tests a simple remote invocation on an object. It is a
     no-tasking client. A reference to the object is built from a
     stringified reference (or `IOR'), which is passed on command line.


          ------------------------------------------------------------------------------
          --                                                                          --
          --                           POLYORB COMPONENTS                             --
          --                                                                          --
          --                               C L I E N T                                --
          --                                                                          --
          --                                 B o d y                                  --
          --                                                                          --
          --         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
          --                                                                          --
          -- This is free software;  you can redistribute it  and/or modify it  under --
          -- terms of the  GNU General Public License as published  by the Free Soft- --
          -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
          -- sion.  This software is distributed in the hope  that it will be useful, --
          -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
          -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
          -- License for  more details.                                               --
          --                                                                          --
          -- As a special exception under Section 7 of GPL version 3, you are granted --
          -- additional permissions described in the GCC Runtime Library Exception,   --
          -- version 3.1, as published by the Free Software Foundation.               --
          --                                                                          --
          -- You should have received a copy of the GNU General Public License and    --
          -- a copy of the GCC Runtime Library Exception along with this program;     --
          -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
          -- <http://www.gnu.org/licenses/>.                                          --
          --                                                                          --
          --                  PolyORB is maintained by AdaCore                        --
          --                     (email: sales@adacore.com)                           --
          --                                                                          --
          ------------------------------------------------------------------------------

          --   echo client.

          with Ada.Command_Line;
          with Ada.Text_IO;
          with CORBA.ORB;

          with Echo;

          with PolyORB.Setup.Client;
          pragma Warnings (Off, PolyORB.Setup.Client);

          with PolyORB.Utils.Report;

          procedure Client is
             use Ada.Command_Line;
             use Ada.Text_IO;
             use PolyORB.Utils.Report;

             Sent_Msg, Rcvd_Msg : CORBA.String;
             myecho : Echo.Ref;

          begin
             New_Test ("Echo client");

             CORBA.ORB.Initialize ("ORB");
             if Argument_Count /= 1 then
                Put_Line ("usage : client <IOR_string_from_server>|-i");
                return;
             end if;

             --  Getting the CORBA.Object

             CORBA.ORB.String_To_Object
               (CORBA.To_CORBA_String (Ada.Command_Line.Argument (1)), myecho);

             --  Checking if it worked

             if Echo.Is_Nil (myecho) then
                Put_Line ("main : cannot invoke on a nil reference");
                return;
             end if;

             --  Sending message

             Sent_Msg := CORBA.To_CORBA_String (Standard.String'("Hello Ada !"));
             Rcvd_Msg := Echo.echoString (myecho, Sent_Msg);

             --  Printing result

             Put_Line ("I said : " & CORBA.To_Standard_String (Sent_Msg));
             Put_Line ("The object answered : " & CORBA.To_Standard_String (Rcvd_Msg));

             End_Report;

          exception
             when E : CORBA.Transient =>
                declare
                   Memb : CORBA.System_Exception_Members;
                begin
                   CORBA.Get_Members (E, Memb);
                   Put ("received exception transient, minor");
                   Put (CORBA.Unsigned_Long'Image (Memb.Minor));
                   Put (", completion status: ");
                   Put_Line (CORBA.Completion_Status'Image (Memb.Completed));

                   End_Report;
                end;
          end Client;

   * The server code sets up a no-tasking node. The object is
     registered to the `RootPOA'. Then an `IOR' reference is built to
     enable interaction with other nodes.


          ------------------------------------------------------------------------------
          --                                                                          --
          --                           POLYORB COMPONENTS                             --
          --                                                                          --
          --                               S E R V E R                                --
          --                                                                          --
          --                                 B o d y                                  --
          --                                                                          --
          --         Copyright (C) 2002-2012, Free Software Foundation, Inc.          --
          --                                                                          --
          -- This is free software;  you can redistribute it  and/or modify it  under --
          -- terms of the  GNU General Public License as published  by the Free Soft- --
          -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
          -- sion.  This software is distributed in the hope  that it will be useful, --
          -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
          -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
          -- License for  more details.                                               --
          --                                                                          --
          -- As a special exception under Section 7 of GPL version 3, you are granted --
          -- additional permissions described in the GCC Runtime Library Exception,   --
          -- version 3.1, as published by the Free Software Foundation.               --
          --                                                                          --
          -- You should have received a copy of the GNU General Public License and    --
          -- a copy of the GCC Runtime Library Exception along with this program;     --
          -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
          -- <http://www.gnu.org/licenses/>.                                          --
          --                                                                          --
          --                  PolyORB is maintained by AdaCore                        --
          --                     (email: sales@adacore.com)                           --
          --                                                                          --
          ------------------------------------------------------------------------------

          with Ada.Text_IO;

          with CORBA.Impl;
          with CORBA.Object;
          with CORBA.ORB;

          with PortableServer.POA.Helper;
          with PortableServer.POAManager;

          with Echo.Impl;

          with PolyORB.CORBA_P.CORBALOC;

          --  Setup server node: use no tasking default configuration

          with PolyORB.Setup.No_Tasking_Server;
          pragma Warnings (Off, PolyORB.Setup.No_Tasking_Server);

          procedure Server is
          begin

             declare
                Argv : CORBA.ORB.Arg_List := CORBA.ORB.Command_Line_Arguments;

             begin
                CORBA.ORB.Init (CORBA.ORB.To_CORBA_String ("ORB"), Argv);

                declare
                   Root_POA : PortableServer.POA.Local_Ref;

                   Ref : CORBA.Object.Ref;

                   Obj : constant CORBA.Impl.Object_Ptr := new Echo.Impl.Object;

                begin

                   --  Retrieve Root POA

                   Root_POA := PortableServer.POA.Helper.To_Local_Ref
                     (CORBA.ORB.Resolve_Initial_References
                      (CORBA.ORB.To_CORBA_String ("RootPOA")));

                   PortableServer.POAManager.Activate
                     (PortableServer.POA.Get_The_POAManager (Root_POA));

                   --  Set up new object

                   Ref := PortableServer.POA.Servant_To_Reference
                     (Root_POA, PortableServer.Servant (Obj));

                   --  Output IOR

                   Ada.Text_IO.Put_Line
                     ("'"
                      & CORBA.To_Standard_String (CORBA.Object.Object_To_String (Ref))
                      & "'");
                   Ada.Text_IO.New_Line;

                   --  Output corbaloc

                   Ada.Text_IO.Put_Line
                     ("'"
                      & CORBA.To_Standard_String
                      (PolyORB.CORBA_P.CORBALOC.Object_To_Corbaloc (Ref))
                      & "'");

                   --  Launch the server

                   CORBA.ORB.Run;
                end;
             end;
          end Server;


6.6.1.4 Compilation and execution
.................................

To compile this demo,
  1. Process the IDL file with `idlac' (or `iac')
           $ idlac echo.idl

  2. Compile the client node
           $ gnatmake client.adb `polyorb-config`

  3. Compile the server node
           $ gnatmake server.adb `polyorb-config`


Note the use of backticks (`). This means that `polyorb-config' is
first executed, and then the command line is replaced with the output
of the script, setting up library and include paths and library names.

   To run this demo:

   * run `server', the server outputs its IOR, a hexadecimal string
     with the IOR: prefix:
          $ ./server
          Loading configuration from polyorb.conf
          No polyorb.conf configuration file.
          'IOR:01534f410d00000049444c3[..]'

   * In another shell, run `client', passing cut-and-pasting the
     complete IOR on the command line:
          $ ./client 'IOR:01534f410d00000049444c3[..]'
          Echoing string: " Hello Ada ! "
          I said : Hello Ada !
          The object answered : Hello Ada !

6.6.2 Other examples
--------------------

PolyORB provides other examples to test other CORBA features. These
examples are located in the `example/corba' directory in the PolyORB
distribution.

   * `all_functions' tests CORBA parameter passing modes (`in', `out',
     ..);

   * `all_types' tests CORBA types;

   * `echo' is a simple CORBA demo;

   * `random' is a random number generator;

   * `send' tests MIOP specific API.

6.7 Configuring a CORBA application
===================================

To configure a CORBA application, you need to separately configure
PolyORB and the GIOP protocol (or any other protocol personality you
wish to use).

6.7.1 Configuring PolyORB
-------------------------

Please refer to *note Building an application with PolyORB:: for more
information on PolyORB's configuration.

6.7.2 Configuring GIOP protocol stack for PolyORB
-------------------------------------------------

The GIOP protocol is separated from the CORBA application personality.
See *note Configuring the GIOP personality:: for more information on
GIOP's configuration.

6.7.3 Configuring Security services for PolyORB
-----------------------------------------------

PolyORB provides support for some elements of the CORBA Security
mechanisms. This sections lists the corresponding configuration
parameters.

6.7.3.1 Supported mechasnisms
.............................

PolyORB provides support for the following security mechanisms:

  1. SSL/TLS protected transport;

  2. GSSUP (user/password) authentication mechanism;

  3. identity assertion and backward trust evaluation.

6.7.3.2 Compile-time configuration
..................................

To enable security support, applications must `with' one of the
predefined setup packages:

  1. `PolyORB.Setup.Secure_Client' - for client side support only;

  2. `PolyORB.Setup.Secure_Server' - for both client and server side
     support.

6.7.3.3 Run-time configuration
..............................

  1. Capsule configuration

     This section details the configuration parameters for capsule
     configuration.

          [security_manager]
          # List of sections for configure client's credentials
          #own_credentials=my_credentials
          #
          # Client requires integrity proteced messages
          #integrity_required=true
          #
          # Client requires confiodentiality protected messages
          #confidentiality_required=true
          #
          # Client requires security association to detect replay (not supported
          for now)
          #detect_replay_required=true
          #
          # Client requires security association to detect message sequence
          errors (not
          # supported for now)
          #detect_misordering_required=true
          #
          # Client requires target authentication
          #establish_trust_in_target_required=true
          #
          # Client requires client authentication (usually not applicable at
          all)
          #establish_trust_in_client_required=true
          #
          # (rare useful)
          #identity_assertion_required=true
          #
          # (rare useful)
          #delegation_by_client_required=true

  2. Credentials configuration

     This section details configuration parameters for defining a
     program's credentials. Depending on the mechanisms used for the
     transport and authentication layers, the credentials configuration
     section may define configuration only for one transport mechanism
     and/or one authentication mechanism.

          #[my_credentials]
          #
          # TLS protected transport mechanism used as transport mechanism
          #transport_credentials_type=tls
          #
          # Connection method. Available methods: tls1, ssl3, ssl2
          #tls.method=tls1
          #
          # Certificate file name
          #tls.certificate_file=my.crt
          #
          # Certificate chain file name
          #tls.certificate_chain_file=
          #
          # Private key file name
          #tls.private_key_file=my.key
          #
          # Name of file, at which CA certificates for verification purposes are
          #located
          #tls.certificate_authority_file=root.crt
          #
          # Name of directory, at which CA certificates for verification
          #purposes are
          # located
          #tls.certificate_authority_path=
          #
          # List of available ciphers
          #tls.ciphers=ALL
          #
          # Verify peer certificate
          #tls.verify_peer=true
          #
          # Fail if client don't provide ceritificate (server only)
          #tls.verify_fail_if_no_peer_certificate=true
          #
          # GSSUP (user/password) mechanism as authentication mechanism
          #authentication_credentials_type=gssup
          #
          # User name
          #gssup.username=username@domain
          #
          # User password
          #gssup.password=password
          #
          # Target name for which user/password pair is applicable
          #gssup.target_name=@domain

  3. POA configuration

     This section details configuration parameters for defining security
     characteristics of objects managed by POA. The POA's name is used
     as the section name.

          #[MySecurePOA]
          #
          # Unprotected invocations is allowed
          #unprotected_invocation_allowed=true
          #
          # Section name for configuration of used protected transport mechanism
          #(if any)
          #transport_mechanism=tlsiop
          #
          # Section name for configuration of used authentication mechanism (if
          #any)
          #authentication_mechanism=my_gssup
          #
          # Target require client authentication at authentication layer (in
          #addition
          # to authentication at transport layer)
          #authentication_required=true
          #
          # Name of file for backward trust evalutation rules
          #backward_trust_rules_file=file.btr
          #
          # Section name for configuration of authorization tokens authority
          #privilege_authorities=

  4. TLS protected transport mechanism configuration

     This section details configuration parameters for the TLS protected
     transport mechanism. The section name for mechanism configuration
     is defined in the POA configuration.

          [tlsiop]
          # List of access points
          #addresses=127.0.0.1:3456

  5. GSSUP authentication mechanism

     This section details configuration parameters for the GSSUP
     authentication mechanism. The section name for mechanism
     configuration is defined in the POA configuration.

          #[my_gssup]
          #
          # Authentication mechanism
          #mechanism=gssup
          #
          # Target name
          #gssup.target_name=@domain
          #
          # User name/password mapping file
          #gssup.passwd_file=passwd.pwd

6.7.4 Command line arguments
----------------------------

The CORBA specifications define a mechanism to pass command line
arguments to your application, using the `CORBA::ORB:Init' method.

   For now, PolyORB supports the following list of arguments:

   * `InitRef' to pass initial reference.


6.8 Implementation Notes
========================

PolyORB strives to support CORBA specifications as closely as possible.
However, on rare occasions, the implementation adapts the
specifications to actually enable its completion. This section provides
information on the various modifications we made.

6.8.1 Tasking
-------------

PolyORB provides support for tasking and no-tasking, using
configuration parameters. Please refer to *note Building an application
with PolyORB:: for more information on PolyORB's configuration.

   When selecting a tasking-capable runtime, ORB-related functions are
thread safe, following the IDL-to-Ada mapping recommendations.

6.8.2 Implementation of CORBA specifications
--------------------------------------------

In some cases, the CORBA specifications do not describe the semantics
of the interface in sufficient detail. We add an `Implementation Notes'
tag to the package specification to indicate the modifications or
enhancements we made to the standard.

   In some cases, the IDL-to-Ada mapping specifications and the CORBA
specifications conflict. We add an `Implementation Notes' tag to the
package specification to indicate this issue. Whenever possible,
PolyORB follows the CORBA specifications.

6.8.3 Additions to the CORBA specifications
-------------------------------------------

In some cases, the specifications lack features that may be useful. We
add an `Implementation Notes' tag to the package specification to
detail the additions we made to the standard.

   In addition to the above, PolyORB follows some of the recommendations
derived from the OMG Issues for Ada 2003 Revision Task Force mailing
list (see `http://www.omg.org/issues/ada-rtf.html' for more
information).

6.8.4 Interface repository
--------------------------

The documentation of the PolyORB's CORBA Interface Repository will
appear in a future revision of PolyORB.

6.8.5 Policy Domain Managers
----------------------------

You have two ways to register the reference to the CORBA Policy Domain
Manager the application will use:

   * Setting up the `policy_domain_manager' entry in the `[corba]'
     section in your configuration file, `policy_domain_manager' is the
     `IOR' or `corbaloc' of the COS Naming server to use. See *note
     Using a configuration file:: for more details.

   * Registering an initial reference using the `-ORB InitRef
     PolyORBPolicyDomainManager=<IOR>' or `-ORB InitRef
     PolyORBPolicyDomainManager=<corbaloc>' command-line argument. See
     the CORBA specifications for more details.

   * Registering an initial reference for `PolyORBPolicyDomainManager'
     using the `CORBA.ORB.Register_Initial_Reference' function. See the
     CORBA specifications for more details.


6.8.6 Mapping of exceptions
---------------------------

For each exception defined in the CORBA specifications, PolyORB
provides the `Raise_<excp_name>' function, a utility function that
raises the exception `<excp_name>', along with its exception member.
PolyORB also defines the `Get_Members' function (as defined in the
IDL-to-Ada mapping) to provide accessors to retrieve information on the
exception.

   In addition, for each exception defined in a user-defined IDL
specification, the IDL-to-Ada compiler will generate a
`Raise_<excp_name>' function in the Helper package. It is a utility
function that raises the exception `<excp_name>', along with its
exception member.

6.8.7 Additional information to `CORBA::Unknown'
------------------------------------------------

When a CORBA application raises an Ada exception that is not part of
the IDL specifications, nor defined by the CORBA specifications, then
this exception is translated into a `CORBA::UNKNOWN' exception.

   To help debugging CORBA applications, PolyORB supports a specific
service context to the GIOP protocol personality that conveys exception
information. When displaying exception information, server-side
specific exception information is delimited by "<Invocation Exception
Info: ...>"

   Here is an example from the `all_types' example provided by PolyORB.

     Exception name: CORBA.UNKNOWN
     Message: 4F4D0001M
     <Invocation Exception Info: Exception name: CONSTRAINT_ERROR
     Message: all_types-impl.adb:315 explicit raise
     Call stack traceback locations:
     0x84d279c 0x84c1e78 0x84b92c6 0x84b8e9>
     Call stack traceback locations:
     0x81d0425 0x81d0554 0x81d6d8c 0x81fd02b 0x81fc091 0x82eea12 0x83e4c22 0x807b69a 0xb7a15e3e

   Note that call stack tracebacks can be translated into symbolic form
using the `addr2line' utility that comes with GNAT.

6.8.8 Internals packages
------------------------

PolyORB sometimes declares internal types and routines inside CORBA
packages. These entities are gathered into an `Internals' child
package. You should not use these functions: they are not portable, and
may be changed in future releases.

6.9 PolyORB's specific APIs
===========================

PolyORB defines packages to help in the development of CORBA programs.

   * *note PolyORB.CORBA_P.CORBALOC:::

     This package defines a helper function to build a `corbaloc'
     stringified reference from a CORBA object reference.

   * *note PolyORB.CORBA_P.Naming_Tools:::

     This package defines helper functions to ease interaction with
     CORBA COS Naming.

   * *note PolyORB.CORBA_P.Server_Tools:::

     This package defines helper functions to ease set up of a simple
     CORBA Server.


6.9.1 `PolyORB.CORBA_P.CORBALOC'
--------------------------------


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --             P O L Y O R B . C O R B A _ P . C O R B A L O C              --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2004-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- As a special exception under Section 7 of GPL version 3, you are granted --
     -- additional permissions described in the GCC Runtime Library Exception,   --
     -- version 3.1, as published by the Free Software Foundation.               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     --  Helper functions to manage CORBA corbaloc references

     with CORBA.Object;

     package PolyORB.CORBA_P.CORBALOC is

        function Object_To_Corbaloc
          (Obj : CORBA.Object.Ref'Class)
          return CORBA.String;
        --  Convert reference to corbaloc, return corbaloc of best profile

     end PolyORB.CORBA_P.CORBALOC;

6.9.2 `PolyORB.CORBA_P.Naming_Tools'
------------------------------------


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --         P O L Y O R B . C O R B A _ P . N A M I N G _ T O O L S          --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2001-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- As a special exception under Section 7 of GPL version 3, you are granted --
     -- additional permissions described in the GCC Runtime Library Exception,   --
     -- version 3.1, as published by the Free Software Foundation.               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     --  Wrappers for the COS Naming service to facilitate retrievel of object
     --  references by IOR or by name.

     with Ada.Finalization;

     with CORBA.Object;
     with CosNaming.NamingContext;

     package PolyORB.CORBA_P.Naming_Tools is

        function Locate (Name : CosNaming.Name) return CORBA.Object.Ref;

        function Locate
          (Context : CosNaming.NamingContext.Ref;
           Name    : CosNaming.Name) return CORBA.Object.Ref;
        --  Locate an object given its name, given as an array of name components.

        function Locate
          (IOR_Or_Name : String; Sep : Character := '/') return CORBA.Object.Ref;

        function Locate
          (Context     : CosNaming.NamingContext.Ref;
           IOR_Or_Name : String;
           Sep         : Character := '/') return CORBA.Object.Ref;
        --  Locate an object by IOR or name. If the string does not start with
        --  "IOR:", the name will be parsed before it is looked up, using
        --  Parse_Name below.

        procedure Register
          (Name   : String;
           Ref    : CORBA.Object.Ref;
           Rebind : Boolean := False;
           Sep    : Character := '/');
        --  Register an object by its name by binding or rebinding.
        --  The name will be parsed by Parse_Name below; any necessary contexts
        --  will be created on the name server.
        --  If Rebind is True, then a rebind will be performed if the name
        --  is already bound.

        procedure Unregister (Name : String);
        --  Unregister an object by its name by unbinding it

        type Server_Guard is limited private;
        procedure Register
          (Guard  : in out Server_Guard;
           Name   : String;
           Ref    : CORBA.Object.Ref;
           Rebind : Boolean := False;
           Sep    : Character := '/');
        --  A Server_Guard object is an object which is able to register a server
        --  reference in a naming service (see Register above), and destroy this
        --  name using Unregister when the object disappears (the program terminates
        --  or the Server_Guard object lifetime has expired).

        function Parse_Name
          (Name : String;
           Sep : Character := '/') return CosNaming.Name;
        --  Split a sequence of name component specifications separated with Sep
        --  characters into a name component array. Any leading Sep is ignored.

     private
        --  implementation removed
     end PolyORB.CORBA_P.Naming_Tools;

6.9.3 `PolyORB.CORBA_P.Server_Tools'
------------------------------------


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --         P O L Y O R B . C O R B A _ P . S E R V E R _ T O O L S          --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2001-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- As a special exception under Section 7 of GPL version 3, you are granted --
     -- additional permissions described in the GCC Runtime Library Exception,   --
     -- version 3.1, as published by the Free Software Foundation.               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     --  Helper functions for CORBA servers. Note that using this unit implies
     --  using the Portable Object Adapter.

     with CORBA.Object;
     with PortableServer.POA;

     package PolyORB.CORBA_P.Server_Tools is

        pragma Elaborate_Body;

        type Hook_Type is access procedure;
        Initiate_Server_Hook : Hook_Type;
        --  Access to a procedure to be called upon start up.
        --  See Initiate_Server for more details.

        procedure Activate_Server;
        --  Start a new ORB, and initialize the Root POA.
        --
        --  If the Initiate_Server_Hook variable is not null, the designated
        --  procedure will be called after initializing the ORB.

        procedure Initiate_Server (Start_New_Task : Boolean := False);
        --  Calls Activate_Server then starts ORB main loop.
        --  If Start_New_Task is True, a new task will be created and control will
        --  be returned to the caller. Otherwise, the ORB main loop will be executed
        --  in the current context.

        function Get_Root_POA return PortableServer.POA.Local_Ref;
        --  Return the Root_POA attached to the current ORB instance.

        procedure Initiate_Servant
          (S : PortableServer.Servant;
           R : out CORBA.Object.Ref'Class);
        --  Initiate a servant: register a servant to the Root POA.
        --  If the Root POA has not been initialized, initialize it.

        procedure Reference_To_Servant
          (R : CORBA.Object.Ref'Class;
           S : out PortableServer.Servant);
        --  Convert a CORBA.Object.Ref into a PortableServer.Servant.

        procedure Servant_To_Reference
          (S : PortableServer.Servant;
           R : out CORBA.Object.Ref'Class);
        --  Convert a PortableServer.Servant into CORBA.Object.Ref.

        procedure Initiate_Well_Known_Service
          (S    : PortableServer.Servant;
           Name : String;
           R    : out CORBA.Object.Ref'Class);
        --  Make S accessible through a reference appropriate for
        --  generation of a corbaloc URI with a named key of Name.

     end PolyORB.CORBA_P.Server_Tools;

7 RT-CORBA
**********

7.1 What you should know before Reading this section
====================================================

This section assumes that the reader is familiar with the Real-Time
CORBA specifications described in `[OMG02a]' and `[OMG03]'.

7.2 Installing RT-CORBA
=======================

The RT-CORBA library is installed as part of the installation of the
CORBA personality. Note that you may have to select specific run-time
options to enable full compliance with RT-CORBA specifications and
ensure real time behavior.

7.3 Configuring RT-CORBA
========================

This section details how to configure your application to use the
RT-CORBA library.

7.3.1 `PolyORB.RTCORBA_P.Setup'
-------------------------------

The RT-CORBA specifications mandate that the implementation provide a
mechanism to set up some of its internals.

   The package `PolyORB.RTCORBA_P.Setup' provides an API to set up the
`PriorityMapping' and `PriorityTransform' objects.


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --              P O L Y O R B . R T C O R B A _ P . S E T U P               --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2003-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- As a special exception under Section 7 of GPL version 3, you are granted --
     -- additional permissions described in the GCC Runtime Library Exception,   --
     -- version 3.1, as published by the Free Software Foundation.               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     --  Implementation Notes: RTCORBA specifications defines objects that
     --  are (Ada) programming language objects rather than CORBA
     --  objects. Therefore the normal mechanism for coupling an
     --  implementation to the code that uses it (an object reference) does
     --  not apply. The implementation must provide specific mechanisms to
     --  enable this coupling.
     --
     --  This package provides accessors to configure them. It supports the
     --  following objects:
     --  * PriorityMapping
     --  * PriorityTransform

     with RTCORBA.PriorityMapping;
     with RTCORBA.PriorityTransform;

     package PolyORB.RTCORBA_P.Setup is

        --  PriorityMapping

        type PriorityMapping_Access is
          access all RTCORBA.PriorityMapping.Object'Class;

        procedure Set_Priority_Mapping
          (Mapping : RTCORBA.PriorityMapping.Object'Class);
        pragma Inline (Set_Priority_Mapping);
        --  Set RT-ORB PriorityMapping object,
        --  overrides previous settings, if any.

        function Get_Priority_Mapping return PriorityMapping_Access;
        pragma Inline (Get_Priority_Mapping);
        --  Return RT-ORB PriorityMapping object.

        --  PriorityTransform

        type PriorityTransform_Access is
          access all RTCORBA.PriorityTransform.Object'Class;

        procedure Set_Priority_Transform
          (Transform : RTCORBA.PriorityTransform.Object'Class);
        pragma Inline (Set_Priority_Transform);
        --  Set RT-ORB global Priority Mapping object,
        --  overrides previous settings, if any.

        function Get_Priority_Transform return PriorityTransform_Access;
        pragma Inline (Get_Priority_Transform);
        --  Return RT-ORB global Priority Mapping object.

     end PolyORB.RTCORBA_P.Setup;

7.4 `RTCORBA.PriorityMapping'
=============================

PolyORB provides different implementations of this specification:

   * `RTCORBA.PriorityMapping.Direct' maps CORBA priorities directly to
     native priorities. If the CORBA priority is not in
     `System.Priority'Range', then the mapping is not possible.

   * `RTCORBA.PriorityMapping.Linear' maps each individual native
     priority to a contiguous range of CORBA priorities, so that the
     complete CORBA priority range is used up for the mapping. See
     `rtcorba-prioritymapping-linear.adb' for more details.


7.5 RTCosScheduling Service
===========================

7.5.1 Overview
--------------

PolyORB provides an implementation of the RTCosScheduling service
defined in `[OMG02a]'.

   PolyORB uses some permissions stated in the specifications to allow
for easy configuration of `ClientScheduler' and `ServerScheduler',
defined in the following sections.

   Additional information on the use of the API may be found in the
RTCosScheduling example in `examples/corba/rtcorba/rtcosscheduling'.

7.5.2 `RTCosScheduling::ClientScheduler'
----------------------------------------

Client side activities are defined in a configuration file that can be
loaded using
`RTCosScheduling.ClientScheduler.Impl.Load_Configuration_File'

   On the client side, the user can set up

   * current task priority, using registered `PriorityMapping' object.


This file has the following syntax, derived from PolyORB configuration
file syntax:

     # Name of the activity
     [activity activity1]

     # Activity priority, in RTCORBA.Priority'Range
     priority=10000

In this example, activity `activity1' is defined with priority `10'000'.

7.5.3 `RTCosScheduling::ServerScheduler'
----------------------------------------

Server side POAs and objects are defined in a configuration file that
can be loaded using
`RTCosScheduling.ClientScheduler.Impl.Load_Configuration_File'

   On the server side, the user can set up

   * object priority, using registered `PriorityMapping' object.

   * all RT-CORBA-specific POA configuration parameters.


This file has the following syntax, derived from PolyORB configuration
file syntax:

     # Name of the object
     [object object1]

     # Object priority, in RTCORBA.Priority'Range
     priority=10000

In this example, object `object1' is defined with priority `10'000'.

     # Name of the POA
     [poa poa1]

     # PriorityModelPolicy for POA
     priority_model=CLIENT_PROPAGATED
     default_priority=0 # not meaningful for CLIENT_PROPAGATED

     # Threadpools attached to POA
     threadpool_id=1

     # Name of the POA
     [poa poa2]

     # PriorityModelPolicy for POA
     priority_model=SERVER_DECLARED
     default_priority=40

     # Threadpools attached to POA
     threadpool_id=2

     # Name of the POA
     [poa poa3]

     # POA with no defined policies

In this example, Two POAs are defined: POA `poa1' will use the
`CLIENT_PROPAGATED' PriorityModel Policy, default value is not
meaningful for this configuration, `poa1' will use the Threadpool #1;
POA `poa2' will use the `SERVER_DECLARED' PriorityModel Policy, default
server priority is 40, `poa2' will use the Threadpool #2. Note that
both policies are optional and can be omitted.

8 Ada Distributed Systems Annex (DSA)
*************************************

8.1 Introduction to the Ada DSA
===============================

A critical feature of the Distributed Systems Annex (DSA) is that it
allows the user to develop his application the same way whether this
application is going to be executed as several programs on a
distributed system, or as a single program on a non-distributed system.
The DSA has been designed to minimize the source changes needed to
convert an ordinary non-distributed program into a distributed program.

   The simplest way to start with DSA is to develop the application on
a non-distributed system. Of course, the design of the application
should take into account the fact that some units are going to be
accessed remotely. In order to write a distributed Ada program, it is
necessary for the user to label by means of categorization pragmas some
of library level compilation units of the application program. The units
that require categorization are typically those that are called
remotely, and those that provide the types used in remote invocations.

   In order to ensure that distributed execution is possible, these
units are restricted to contain only a limited set of Ada constructs.
For instance, if the distributed system has no shared memory, shared
variables must be forbidden. To specify the nature of these
restrictions, the DSA provides several categorization pragmas, each of
which excludes some language constructs from the categorized package.

   Of course, the user can develop the non-distributed application with
his usual software engineering environment. It is critical to note that
the user needs no specialized tools to develop his/her distributed
application. For instance, he can debug his application with the usual
debugger. Note that a non-distributed program is not to be confused with
a distributed application composed of only one program. The latter is
built with the help of the configuration tool and includes the
communication library.

   Once the non-distributed version of the program is complete, it has
to be configured into separate partitions. This step is surprisingly
simple, compared to that of developing the application itself. The
configuration step consists of mapping sets of compilation units into
individual partitions, and specifying the mapping between partitions and
nodes in the computer network. This mapping is specified and managed by
means of a gnatdist configuration.

   The distributed version of the user application should work as is,
but even when a program can be built both as a non-distributed or a
distributed program using the same source code, there may still be
differences in program execution between the distributed and
non-distributed versions. These differences are discussed in subsequent
sections (see *note Pragma Asynchronous:: and *note Pragma
All_Calls_Remote::).

   Developing a non-distributed application in order to distribute it
later is the natural approach for a novice. Of course, it is not always
possible to write a distributed application as a non-distributed
application. For instance, a client/server application does not belong
to this category because several instances of the client can be active
at the same time. It is very easy to develop such an application using
PolyORB; we shall describe how to do this in the following sections.

8.1.1 Architecture of a Distributed Ada Application
---------------------------------------------------

A distributed system is an interconnection of one or more processing
nodes and zero or more storage nodes. A distributed program comprises
one or more partitions. A partition is an aggregate of library units.
Partitions communicate through shared data or RPCs. A passive partition
has no thread of control. Only a passive partition can be configured on
a storage node. An active partition has zero or more threads of control
and has to be configured on a processing node.

   The library unit is the core component of a distributed Ada
application. The user can explicitly assign library units to a
partition. Partitioning is a post-compilation process. The user
identifies interface packages at compile-time. These packages are
categorized using pragmas. Each of these pragmas supports the use of
one of the following classical paradigms:

   * Remote subprograms: For the programmer, a remote subprogram call
     is similar to a regular subprogram call. Run-time binding using
     access-to-subprogram types can also be used with remote
     subprograms. These remote subprograms are declared in library
     units categorized as remote call interface (RCI).

   * Distributed objects: Special-purpose access types can designate
     remote objects. When a primitive dispatching operation is invoked
     on an object designated by such a remote access, a remote call is
     performed transparently on the partition on which the object
     resides. The types of these distributed objects are declared in
     library units categorized as remote types (RT).

   * Shared objects: Global data can be shared among active partitions,
     providing a repository similar to shared memory, a shared file
     system or a database. Entryless protected objects allow safe
     concurrent access and update of shared objects. This feature is
     orthogonal to the notion of distributed objects, which are only
     accessed through exported services. These shared objects are
     declared in library units categorized as shared passive (SP).


   The remotely-called subprograms declared in a library unit
categorized as remote call interface (RCI) or remote types (RT) may be
either statically or dynamically bound. The partition on which a
statically bound remote subprogram is executed can be determined before
the call. This is a static remote subprogram call. In contrast, a
remote method or a dereference of an access to remote subprogram are
dynamically bound remote calls, because the partition on which the
remote subprogram is executed is determined at runtime, by the actuals
of the call.

   In the following example, Data_1 and Data_2 are shared passive (SP)
library units. Data_1 is configured on a passive partition mapped on a
storage node. Partition_1 and Partition_2 are active partitions. Note
that under some circumstances, a partition, for instance Partition_2,
can be duplicated. To be duplicated, Unit_2 and Unit_3 which are
configured on Partition_2 have to provide only dynamically bound remote
subprograms. Otherwise, a partition calling a remote subprogram on
Unit_2 would not be able to statically determine where to perform the
remote call between the two instances of Unit_2.

 8.1.2 Categorization Pragmas
----------------------------

Library units can be categorized according to the role they play in a
distributed program. A categorization pragma is a library unit pragma
that restricts the kinds of declarations that can appear in a library
unit and possibly in its child units, as well as the legal semantic
dependences that the categorized unit can have. There are several
categorization pragmas:

   * Remote_Call_Interface

   * Remote_Types

   * Shared_Passive

   * Pure

   The following paragraphs do not present the detailed semantics of
these pragmas (formal details will be found in the Ada Reference
Manual).  Their purpose is to give the reader an intuitive overview of
the purpose of these pragmas. If a library unit is not categorized, this
unit is called a normal unit and plays no special role in the
distributed application. Such a unit is duplicated on any partition in
which it is mentioned.

   A parenthetical remark: to avoid the need for specific run-time
libraries for the DSA, the notion of remote rendezvous does not exist
in Ada: tasks cannot be invoked directly from one partition to another.
Therefore, declarations of task types and general protected types with
entries are not allowed in categorized Ada library units.

8.1.3 Pragma Declared Pure
--------------------------

This pragma is not specific to the Distributed Systems Annex. A pure
package can appear in the context of any package, categorized or not.
A pure package is a preelaborable package that does not contain
variable data.  It is particularly useful to define types, constants and
subprograms shared by several categorized packages. In contrast, normal
packages cannot appear in the context of categorized package
declarations.  Because a pure package has no state, it can be
duplicated on several partitions.

8.1.4 Pragma Remote_Call_Interface
----------------------------------

8.1.4.1 Overview of Pragma Remote_Call_Interface
................................................

Library units categorized with this pragma declare subprograms that can
be called and executed remotely. An RCI unit acts as a server for
remote calls.  There is no memory space shared between server and
clients.  A subprogram call that invokes one such subprogram is a
classical RPC operation; it is a statically bound operation, because
the compiler can determine the identity of the subprogram being called.

   Dynamically bound calls are provided through two mechanisms:

   * The dereference of an access-to-subprogram value, i.e. a value
     whose type is a remote access-to-subprogram (RAS).

   * A dispatching call whose controlling argument is an
     access-to-class-wide operand.  The formal is a remote
     access-to-class-wide (RACW) type. These remote access types can be
     declared in RCI packages as well.


   A remote access type (RAS or RACW) can be viewed as a fat pointer,
that is to say a structure with a remote address and a local address
(like an URL: <protocol>://<remote`-'machine>/<local`-'directory>). The
remote address must denote the host of the partition on which the
entity has been created; the local address describes the local memory
address within the host.

   It is very unlikely that RCI units can be duplicated in the
distributed system. An implementation may allow separate copies of a
RCI unit as long as it ensures that the copies present a consistent
state to all clients.  In the general case, preserving consistency is
very costly. For this reason, the implementation may require a RCI unit
to be unique in the distributed system.

8.1.4.2 Regular Remote Subprograms (RCI)
........................................

In the following example, a RCIBank offers several remote services:
Balance, Transfer, Deposit and Withdraw. On the caller side, the bank
client uses the stub files of unit RCIBank. On the receiver side, the
bank receiver uses the skeleton files of unit RCIBank including the
body of this package.


     package Types is
        pragma Pure;

        type Customer_Type is new String;
        type Password_Type is new String;
     end Types;


     with Types; use Types;
     package RCIBank is
        pragma Remote_Call_Interface;

        function Balance
          (Customer : in Customer_Type;
           Password : in Password_Type)
           return Integer;

        procedure Transfer
          (Payer    : in Customer_Type;
           Password : in Password_Type;
           Amount   : in Positive;
           Payee    : in Customer_Type);

        procedure Deposit
          (Customer : in Customer_Type;
           Amount   : in Positive);

        procedure Withdraw
          (Customer : in Customer_Type;
           Password : in Password_Type;
           Amount   : in out Positive);
     end RCIBank;


     with Types; use Types;
     with RCIBank; use RCIBank;
     procedure RCIClient is
        B : Integer;
        C : Customer_Type := "rich";
        P : Password_Type := "xxxx";
     begin
        B := Balance (C, P);
     end RCIClient;

8.1.4.3 Remote Access to Subprograms (RAS)
..........................................

In the following example, several mirroring banks offer their services
through the same database. Each bank registers a reference to each of
its services with a central bank. A client of the central bank requests
a service from one of the mirroring banks. To satisfy requests, the RCI
unit RASBank defines Balance_Type, a remote access to subprogram.
(Recall that an access type declared in a remote unit has to be either
remote access to subprogram or remote access to class wide type).

   Note that to obtain a remote access to subprogram, the subprogram
that delivers the remote access must be remote itself. Therefore,
MirrorBank is a RCI library unit.


     with Types; use Types;
     package RASBank is
        pragma Remote_Call_Interface;

        type Balance_Type is access function
          (Customer : in Customer_Type;
           Password : in Password_Type)
           return Integer;

        procedure Register
           (Balance : in Balance_Type);

        function Get_Balance
           return Balance_Type;

        --  [...] Other services
     end RASBank;

   In the code below, a mirroring bank registers its services to the
central bank.


     with Types; use Types;
     package MirrorBank is
        pragma Remote_Call_Interface;

        function Balance
          (Customer : in Customer_Type;
           Password : in Password_Type)
           return Integer;

        --  [...] Other services
     end MirrorBank;


     with RASBank, Types; use RASBank, Types;
     package body MirrorBank is

        function Balance
          (Customer : in Customer_Type;
           Password : in Password_Type)
           return Integer is
        begin
           return Something;
        end Balance;

     begin
        --  Register a dynamically bound remote subprogram (Balance)
        --  through a statically bound remote subprogram (Register)
        Register (Balance'Access);
        --  [...] Register other services
     end MirrorBank;

   In the code below, a central bank client asks for a mirroring bank
and calls the Balance service of this bank by dereferencing a remote
access type.


     with Types; use Types;
     with RASBank; use RASBank;
     procedure BankClient is
        B : Integer;
        C : Customer_Type := "rich";
        P : Password_Type := "xxxx";
     begin
        --  Through a statically bound remote subprogram (Get_Balance), get
        --  a dynamically bound remote subprogram. Dereference it to
        --  perform a dynamic invocation.
        B := Get_Balance.all (C, P);
     end BankClient;

8.1.4.4 Remote Access to Class Wide Types (RACW)
................................................

A bank client is now connected to a bank through a terminal. The bank
wants to notify a connected client, by means of a message on its
terminal, when another client transfers a given amount of money to its
account. In the following example, a terminal is designed as a
distributed object. Each bank client will register its terminal object
to the bank server for further use. In the code below, Term_Type is the
root type of the distributed terminal hierarchy.


     with Types; use Types;
     package Terminal is
        pragma Pure;

        type Term_Type is abstract tagged limited private;

        procedure Notify
          (MyTerm   : access Term_Type;
           Payer    : in Customer_Type;
           Amount   : in Integer) is abstract;

     private
        --  implementation removed
     end Terminal;

   In the code below, the RCI unit RACWBank defines Term_Access, a
remote access to class wide type. Term_Access becomes a reference to a
distributed object. In the next section, we will see how to derive and
extend Term_Type, how to create a distributed object and how to use a
reference to it.


     with Terminal, Types; use Terminal, Types;
     package RACWBank is
        pragma Remote_Call_Interface;

        type Term_Access is access all Term_Type'Class;

        procedure Register
          (MyTerm   : in Term_Access;
           Customer : in Customer_Type;
           Password : in Password_Type);

        --  [...] Other services
     end RACWBank;

8.1.4.5 Summary of Pragma Remote_Call_Interface
...............................................

Remote call interface units:

   * Allow subprograms to be called and executed remotely

   * Allow statically bound remote calls (remote subprogram)

   * Allow dynamically bound remote calls (remote access types)

   * Forbid variables and non-remote access types

   * Prevent specification from depending on normal units


8.1.5 Pragma Remote_Types
-------------------------

8.1.5.1 Overview of Pragma Remote_Types
.......................................

Unlike RCI units, library units categorized with this pragma can define
distributed objects and remote methods on them. Both RCI and RT units
can define a remote access type as described above (RACW). A subprogram
defined in a RT unit is not a remote subprogram. Unlike RCI units, a RT
unit can be duplicated on several partitions, in which case all its
entities are distinct. This unit is duplicated on each partition in
which it is defined.

8.1.5.2 Distributed Object
..........................

If we want to implement the notification feature proposed in the
previous section, we have to derive Term_Type. Such a derivation is
possible in a remote types unit like NewTerminal (see below). Any object
of type New_Term_Type becomes a distributed object and any reference to
such an object becomes a fat pointer or a reference to a distributed
object (see Term_Access declaration in *note Remote Access to Class
Wide Types (RACW)::).


     with Types, Terminal; use Types, Terminal;
     package NewTerminal is
        pragma Remote_Types;

        type New_Term_Type is
           new Term_Type with null record;

        procedure Notify
          (MyTerm   : access New_Term_Type;
           Payer    : in Customer_Type;
           Amount   : in Integer);

        function Current return Term_Access;
     end NewTerminal;

   In the code below, a client registers his name and his terminal with
RACWBank. Therefore, when any payer transfers some money to him,
RACWBank is able to notify the client of the transfer of funds.


     with NewTerminal, RACWBank, Types; use NewTerminal, RACWBank, Types;
     procedure Term1Client is
        MyTerm   : Term_Access   := Current;
        Customer : Customer_Type := "poor";
        Password : Password_Type := "yyyy";
     begin
        Register (MyTerm, Customer, Password);
        --  [...] Execute other things
     end Term1Client;

   In the code below, a second client, the payer, registers his terminal
to the bank and executes a transfer to the first client.


     with NewTerminal, RACWBank, Types; use NewTerminal, RACWBank, Types;
     procedure Term2Client is
        MyTerm   : Term_Access   := Current;
        Payer    : Customer_Type := "rich";
        Password : Password_Type := "xxxx";
        Payee    : Customer_Type := "poor";
     begin
        Register (MyTerm, Payer, Password);
        Transfer (Payer, Password, 100, Payee);
     end Term2Client;

   In the code below, we describe the general design of Transfer.
Classical operations of Withdraw and Deposit are performed. Then,
RACWBank retrieves the terminal of the payee (if present) and invokes a
dispatching operation by dereferencing a distributed object Term. The
reference is examined at run-time, and the execution of this operation
takes place on the partition on which the distributed object resides.


     with Types; use Types;
     package body RACWBank is
        procedure Register
          (MyTerm   : in Term_Access;
           Customer : in Customer_Type;
           Password : in Password_Type) is
        begin
           Insert_In_Local_Table (MyTerm, Customer);
        end Register;

        procedure Transfer
          (Payer    : in Customer_Type;
           Password : in Password_Type;
           Amount   : in Positive;
           Payee    : in Customer_Type)
        is
           --  Find Customer terminal.
           Term : Term_Access
             := Find_In_Local_Table (Payee);
        begin
           Withdraw (Payer, Amount);
           Deposit  (Payee, Amount);
           if Term /= null then
              --  Notify on Payee terminal.
              Notify (Term, Payer, Amount);
           end if;
        end Transfer;

        --  [...] Other services
     end RACWBank;

8.1.5.3 Transmitting Dynamic Structure
......................................


     with Ada.Streams; use Ada.Streams;
     package StringArrayStream is
        pragma Remote_Types;

        type List is private;
        procedure Append (L : access List; O : in String);
        function  Delete (L : access List) return String;

     private
        --  implementation removed
     end StringArrayStream;

   Non-remote access types cannot be declared in the public part of a
remote types unit. However, it is possible to define private non-remote
access types as long as the user provides its marshalling procedures,
that is to say the mechanism needed to place a value of the type into a
communication stream.  The code below describes how to transmit a linked
structure.

   The package declaration provides a type definition of single-linked
lists of unbounded strings. An implementation of the marshalling
operations could be the following:


     package body StringArrayStream is
        procedure Read
          (S : access Root_Stream_Type'Class;
           L : out List) is
        begin
           if Boolean'Input (S) then
              L := new Node;
              L.Content := new String'(String'Input (S));
              List'Read (S, L.Next);
           else
              L := null;
           end if;
        end Read;

        procedure Write
          (S : access Root_Stream_Type'Class;
           L : in List) is
        begin
           if L = null then
              Boolean'Output (S, False);
           else
              Boolean'Output (S, True);
              String'Output (S, L.Content.all);
              List'Write (S, L.Next);
           end if;
        end Write;

        --  [...] Other services
     end StringArrayStream;

8.1.5.4 Summary of Remote Types Units
.....................................

Remote types units:

   * Support the definition of distributed objects

   * Allow dynamically bound remote calls (via remote access types)

   * Allow non-remote access types (with marshalling subprograms)

   * Cannot have a specification that depends on normal units


8.1.6 Pragma Shared_Passive
---------------------------

8.1.6.1 Overview of Pragma Shared_Passive
.........................................

The entities declared in such a categorized library unit are intended to
be mapped on a virtual shared address space (file, memory, database).
When two partitions use such a library unit, they can communicate by
reading or writing the same variable in the shared unit. This supports
the conventional shared variables paradigm.  Entryless protected
objects can be declared in these units, to provide an atomic access to
shared data, thus implementing a simple transaction mechanism. When the
address space is a file or a database, the user can take advantage of
the persistency features provided by these storage nodes.

8.1.6.2 Shared and Protected Objects
....................................

In the code below, we define two kinds of shared objects.
External_Synchronization requires that the different partitions
updating this data synchronize to avoid conflicting operations on shared
objects. Internal_Synchronization provides a way to get an atomic
operation on shared objects. Note that only entryless protected types
are allowed in a shared passive unit; synchronization must be done with
protected procedures.


     package SharedObjects is
        pragma Shared_Passive;

        Max : Positive := 10;
        type Index_Type is range 1 .. Max;
        type Rate_Type is new Float;

        type Rates_Type is array (Index_Type) of Rate_Type;

        External_Synchronization : Rates_Type;

        protected Internal_Synchronization is
           procedure Set
             (Index : in Index_Type;
              Rate  : in Rate_Type);

           procedure Get
             (Index : in Index_Type;
              Rate  : out Rate_Type);
        private
        --  implementation removed
     end SharedObjects;

8.1.6.3 Summary of Pragma Shared_Passive
........................................

Shared passive units:

   * Allow direct access to data from different partitions

   * Provide support for shared (distributed) memory

   * Support memory protection by means of entryless protected objects

   * Prevent specification from depending on normal units


8.1.7 More About Categorization Pragmas
---------------------------------------

8.1.7.1 Variables and Non-Remote Access Types
.............................................

In RT or RCI package declarations, variable declarations are forbidden,
and non-remote access types are allowed as long as their marshalling
subprograms are explicitly provided (see *note Transmitting Dynamic
Structure::).

8.1.7.2 RPC Failures
....................

Calls are executed at most once: they are made exactly one time or they
fail with an exception. When a communication error occurs,
System.RPC.Communication_Error is raised.

8.1.7.3 Exceptions
..................

Any exception raised in a remote method or subprogram call is propagated
back to the caller. Exception semantics are preserved in the regular
Ada way.


     package Internal is
        Exc : exception;
     end Internal;


     package RemPkg2 is
        pragma Remote_Call_Interface;

        procedure Subprogram;
     end RemPkg2;


     package RemPkg1 is
        pragma Remote_Call_Interface;

        procedure Subprogram;
     end RemPkg1;

   Let us say that RemPkg2, Internal and RemExcMain packages are on the
same partition Partition_1 and that RemPkg1 is on partition Partition_2.


     with RemPkg1, Ada.Exceptions; use Ada.Exceptions;
     package body RemPkg2 is
        procedure Subprogram is
        begin
           RemPkg1.Subprogram;
        exception when E : others =>
           Raise_Exception (Exception_Identity (E), Exception_Message (E));
        end Subprogram;
     end RemPkg2;


     with Internal, Ada.Exceptions; use Ada.Exceptions;
     package body RemPkg1 is
        procedure Subprogram is
        begin
           Raise_Exception (Internal.Exc'Identity, "Message");
        end Subprogram;
     end RemPkg1;


     with Ada.Text_IO, Ada.Exceptions; use Ada.Text_IO, Ada.Exceptions;
     with RemPkg2, Internal;
     procedure RemExcMain is
     begin
        RemPkg2.Subprogram;
     exception when E : Internal.Exc =>
        Put_Line (Exception_Message (E)); -- Output "Message"
     end RemExcMain;

   When RemPkg1.Subprogram on Partition_1 raises Internal.Exc, this
exception is propagated back to Partition_2. As Internal.Exc is not
defined on Partition_2, it is not possible to catch this exception
without an exception handler when others. When this exception is
reraised in RemPkg1.Subprogram, it is propagated back to Partition_1.
But this time, Internal.Exc is visible and can be handled as we would
in a single-partition Ada program. Of course, the exception message is
also preserved.

8.1.7.4 Pragma Asynchronous
...........................

By default, a remote call is blocking: the caller waits until the remote
call is complete and the output stream is received.  Just like a normal
(nonremote) call, the caller does not proceed until the call returns.
By contrast, a remote subprogram labeled with pragma Asynchronous
allows statically and dynamically bound remote calls to it to be
executed asynchronously. A call to an asynchronous procedure doesn't
wait for the completion of the remote call, and lets the caller
continue its execution. The remote procedure must have only in
parameters, and any exception raised during the execution of the remote
procedure is lost.

   When pragma Asynchronous applies to a regular subprogram with in
parameters, any call to this subprogram will be executed
asynchronously. The following declaration of
AsynchronousRCI.Asynchronous gives an example.


     package AsynchronousRCI is
        pragma Remote_Call_Interface;

        procedure Asynchronous (X : Integer);
        pragma Asynchronous (Asynchronous);

        procedure Synchronous  (X : Integer);

        type AsynchronousRAS is access procedure (X : Integer);
        pragma Asynchronous (AsynchronousRAS);
     end AsynchronousRCI;


     package AsynchronousRT is
        pragma Remote_Types;

        type Object is tagged limited private;

        type AsynchronousRACW is access all Object'Class;
        pragma Asynchronous (AsynchronousRACW);

        procedure Asynchronous (X : Object);
        procedure Synchronous  (X : in out Object);
        function Create return AsynchronousRACW;

     private
        --  implementation removed
     end AsynchronousRT;

   A pragma Asynchronous may apply to a remote access-to-subprogram
(RAS) type.  An asynchronous RAS can be both asynchronous and
synchronous depending on the designated subprogram. For instance, in
the code below, remote call (1) is asynchronous but remote call (2) is
synchronous.

   A pragma Asynchronous may apply to a RACW as well. In this case, the
invocation of any method with in parameters is always performed
asynchronously. Remote method invocation (3) is asynchronous but remote
method invocation (4) is synchronous.


     with AsynchronousRCI, AsynchronousRT;
     use AsynchronousRCI, AsynchronousRT;
     procedure AsynchronousMain is
        RAS  : AsynchronousRAS;
        RACW : AsynchronousRACW := Create;
     begin
        --  Asynchronous Dynamically Bound Remote Call (1)
        RAS := AsynchronousRCI.Asynchronous'Access;
        RAS (0);  --  Abbrev for RAS.all (0)
        --  Synchronous Dynamically Bound Remote Call (2)
        RAS := AsynchronousRCI.Synchronous'Access;
        RAS (0);
        --  Asynchronous Dynamically Bound Remote Call (3)
        Asynchronous (RACW.all);
        --  Synchronous Dynamically Bound Remote Call (4)
        Synchronous (RACW.all);
     end AsynchronousMain;

   This feature supports the conventional message passing paradigm. The
user must be aware that this paradigm, and asynchronous remote calls in
particular, has several drawbacks:

   * It violates the normal semantics of calls; the caller proceeds
     without awaiting the return. The semantics are more similar to a
     "remote goto" than a remote call

   * It prevents easy development and debugging in a non-distributed
     context

   * It can introduce race conditions


   To illustrate the latter, let us take the following example:


     package Node2 is
        pragma Remote_Call_Interface;

        procedure Send (X : Integer);
        pragma Asynchronous (Send);
     end Node2;


     package body Node2 is
        V : Integer := 0;
        procedure Send (X : Integer) is
        begin
           V := X;
        end Send;
     end Node2;


     package Node1 is
        pragma Remote_Call_Interface;

        procedure Send (X : Integer);
        pragma Asynchronous (Send);
     end Node1;


     with Node2;
     package body Node1 is
        procedure Send (X : Integer) is
        begin
           Node2.Send (X);
        end Send;
     end Node1;


     with Node1, Node2;
     procedure NonDeterministic is
     begin
        Node1.Send (1);
        Node2.Send (2);
     end NonDeterministic;

   Let us say that Main is configured on Partition_0, Node1 on
Partition_1 and Node2 on Partition_2. If Node1.Send and Node2.Send
procedures were synchronous or if no latency was introduced during
network communication, we would have the following RPC order: Main
remotely calls Node1.Send which remotely calls Node2.Send which sets V
to 1. Then, Main remotely calls Node2.Send and sets V to 2.

   Now, let us assume that both Send procedures are asynchronous and
that the connection between Partition_1 and Partition_2 is very slow.
The following scenario can very well occur. Main remotely calls
Node1.Send and is unblocked. Immediately after this call, Main remotely
calls Node2.Send and sets V to 2. Once this is done, the remote call to
Node1.Send completes on Partition_1 and it remotely calls Node2.Send
which sets V to 1.

8.1.7.5 Pragma All_Calls_Remote
...............................

A pragma All_Calls_Remote in a RCI unit forces remote procedure calls
to be routed through the communication subsystem even for a local call.
This eases the debugging of an application in a non-distributed
situation that is very close to the distributed one, because the
communication subsystem (including marshalling and unmarshalling
procedures) can be exercised on a single node.

   In some circumstances, a non-distributed application can behave
differently from an application distributed on only one partition. This
can happen when both All_Calls_Remote and Asynchronous features are used
at the same time (see *note Pragma Asynchronous:: for an example).
Another circumstance occurs when the marshalling operations raise an
exception. In the following example, when unit ACRRCI is a
All_Calls_Remote package, the program raises Program_Error. When unit
ACRRCI is no longer a All_Calls_Remote package, then the program
completes silently.


     with Ada.Streams; use Ada.Streams;
     package ACRRT is
        pragma Remote_Types;
        type T is private;
     private
        --  implementation removed
     end ACRRT;


     package body ACRRT is
        procedure Read
          (S : access Root_Stream_Type'Class;
           X : out T) is
        begin
           raise Program_Error;
        end Read;

        procedure Write
          (S : access Root_Stream_Type'Class;
           X : in T) is
        begin
           raise Program_Error;
        end Write;
     end ACRRT;


     with ACRRT; use ACRRT;
     package ACRRCI is
        pragma Remote_Call_Interface;
        pragma All_Calls_Remote;

        procedure P (X : T);
     end ACRRCI;


     package body ACRRCI is
        procedure P (X : T) is
        begin
           null;
        end P;
     end ACRRCI;


     with ACRRCI, ACRRT;
     procedure ACRMain is
        X : ACRRT.T;
     begin
        ACRRCI.P (X);
     end ACRMain;

8.1.7.6 Generic Categorized Units
.................................


     generic
     package GenericRCI is
        pragma Remote_Call_Interface;

        procedure P;
     end GenericRCI;


     with GenericRCI;
     package RCIInstantiation is new GenericRCI;
     pragma Remote_Call_Interface (RCIInstantiation);


     with GenericRCI;
     package NormalInstantiation is new GenericRCI;

   Generic units may be categorized.  Instances do not automatically
inherit the categorization of their generic units, but they can be
categorized explicitly. If they are not, instances are normal
compilation units. Like any other categorized unit, a categorized
instance must be at the library level, and the restrictions of
categorized units apply on instantiation (in particular on generic
formal parameters).

8.1.7.7 Categorization Unit Dependencies
........................................

Each categorization pragma has very specific visibility rules. As a
general rule, RCI > RT > SP > Pure, where the comparison indicates
allowed semantic dependencies. This means that a Remote_Types package
can make visible in its specification only Remote_Types, Shared_Passive
and Pure units.

8.2 Partition Communication Subsystem
=====================================

8.2.1 Marshalling and Unmarshalling Operations
----------------------------------------------

The Partition Communication Subsystem (PCS) is the runtime library for
distributed features. It marshals and unmarshals client and server
requests into a data stream suitable for network transmission.

   Parameter streams are normally read and written using four
attributes:

   * Write: write an element into a stream, valid only for constrained
     types

   * Read: read a constrained element from a stream

   * Output: same as Write, but write discriminants or array bounds as
     well if needed

   * Input: same as Read, but read discriminants or bounds from   the
     stream (the Input attribute denotes a function)

   An Ada compiler provides default 'Read and 'Write operations. But it
is up to the implementation of the PCS to provide default 'Read and
'Write to ensure proper operation between heterogeneous architectures
(see *note Heterogeneous System::).

   The user can override these operations, except for predefined types.
Overriding with a custom version provides the user with a way to debug
its application (even outside of the Distributed Systems Annex). On the
other hand, remaining with the default implementation allows the user
to take advantage of optimized and portable representations provided by
the PCS.


     with Ada.Streams; use Ada.Streams;
     package New_Integers is
        pragma Pure;

        type New_Integer is new Integer;

        procedure Read
          (S : access Root_Stream_Type'Class;
           V : out New_Integer);
        procedure Write
          (S : access Root_Stream_Type'Class;
           V : in New_Integer);

        for New_Integer'Read  use Read;
        for New_Integer'Write use Write;
     end New_Integers;


     package body New_Integers is
        procedure Read
          (S : access Root_Stream_Type'Class;
           V : out New_Integer)
        is
           B : String := String'Input (S);
        begin
           V := New_Integer'Value (B);
        end Read;

        procedure Write
          (S : access Root_Stream_Type'Class;
           V : in New_Integer)
        is
        begin
           String'Output (S, New_Integer'Image (V));
        end Write;
     end New_Integers;

   The language forces the user to provide Read and Write operations for
non-remote access types. Transmitting an access value by dumping its
content into a stream makes no sense when the value is going to be
transmitted to another partition (with a different memory space). To
transmit non-remote access types see *note Transmitting Dynamic
Structure::.

8.2.2 Incorrect Remote Dispatching
----------------------------------

When a remote subprogram takes a class wide argument, there is a risk of
using an object of a derived type that will not be clean enough to be
transmitted. For example, given a type called Root_Type, if a remote
procedure takes a Root_Type'Class as an argument, the user can call it
with an instance of Derived_Type that is Root_Type enriched with a field
of a task type. This will lead to a non-communicable type to be
transmitted between partitions.

   To prevent this, paragraph E.4(18) of the Ada Reference Manual
explains that any actual type used as parameter for a remote call whose
formal type is a class wide type must be declared in the visible part
of a Pure or Remote_Types package. This property also holds for remote
functions returning class wide types. To summarize, the actual type
used should have been eligible for being declared where the root type
has been declared. If a `bad' object is given to a remote subprogram,
Program_Error will be raised at the point of the call.

8.2.3 Partition Ids
-------------------

U'Partition_ID identifies the partition where the unit U has been
elaborated. For this purpose, the PCS provides an integer type
Partition_ID to uniquely designate a partition. Note that a Partition_ID
is represented as a universal integer, and has no meaning outside of the
PCS. The RM requires that two partitions of a distributed program have
different Partition_ID's at a given time. A Partition_ID may or may not
be assigned statically (at compile or link time). A Partition_ID may or
may not be related to the physical location of the partition.

   Partition_ID's can be used to check whether a RCI package is
configured locally.


     with RCI;
     with Ada.Text_IO;
     procedure Check_PID is
     begin
        if RCI'Partition_ID = Check_PID'Partition_ID then
           Ada.Text_IO.Put_Line ("package RCI is configured locally");
        else
           Ada.Text_IO.Put_Line ("package RCI is configured remotely");
        end if;
     end Check_PID;

8.2.4 Concurrent Remote Calls
-----------------------------

It is not defined by the PCS specification whether one or more threads
of control should be available to process incoming messages and to wait
for their completion. But the PCS implementation is required to be
reentrant, thereby allowing concurrent calls on it to service concurrent
remote subprogram calls into the server partition.  This means that at
the implementation level the PCS manages a pool of helper tasks. This
(apart from performance) is invisible to the user.

8.2.5 Consistency and Elaboration
---------------------------------

A library unit is consistent if the same version of its declaration is
used in all units that reference it. This requirement applies as well to
a unit that is referenced in several partitions of a distributed
program.  If a shared passive or RCI library unit U is included in some
partition P, It is a bounded error to elaborate another partition P1 of
a distributed program that that depends on a different version of U.  As
a result of this error, Program_Error can be raised in one or both
partitions during elaboration.

   U'Version yields a string that identifies the version of the unit
declaration and any unit declaration on which it depends. U'Version_Body
yields a string that identifies the version of the unit body. These
attributes are used by the PCS to verify the consistency of an
application.

   After elaborating the library units, but prior to invoking the main
subprogram, the PCS checks the RCI unit versions, and then accept any
incoming RPC. To guarantee that it is safe to call receiving stubs, any
incoming RPC is kept pending until the partition completes its
elaboration.

8.2.6 Abortion and Termination
------------------------------

If a construct containing a remote call is aborted, the remote
subprogram call is cancelled. Whether the execution of the remote
subprogram is immediately aborted as a result of the cancellation is
implementation defined.

   An active partition terminates when its environment task terminates.
In other terms, a partition cannot terminate before the Ada program
itself terminates. The standard termination mechanism applies, but can
be extended with extra rules (see *note Partition Attribute
Termination:: for examples).

8.3 Most Features in One Example
================================

The example shown on the following figure highlights most of the
features of DSA. The system is based on a set of factories and workers
and a storage.  Each entity is a partition itself. A factory hires a
worker from a pool of workers (hire - 1) and assigns a job (query - 2)
to him. The worker performs the job and saves the result (reply - 3) in
a storage common to all the factories.  The worker notifies the factory
of the end of his job (notify - 4).

 When a worker has completed his job, the result must be saved in a
common storage. To do this, we define a protected area in SP package
Storage (see following code). An entryless protected object ensures
atomic access to this area.


     package Storage is
        pragma Shared_Passive;

        protected Queue is
           procedure Insert (Q, R : Integer);
           procedure Remove
             (Q : in Integer;
              R : out Integer);
        private
        --  implementation removed
     end Storage;

   Common is a Remote_Types package that defines most of the remote
services of the above system (see following code). First, we define a
way for the workers to signal the completion of his job. This callback
mechanism is implemented using RAS Notify.


     with Storage; use Storage;
     package Common is
        pragma Remote_Types;

        type Notify is
           access procedure (Q : Integer);
        pragma Asynchronous (Notify);

        type Worker is
           abstract tagged limited private;
        procedure Assign
          (W : access Worker;
           Q : in Integer;
           N : in Notify) is abstract;

        type Any_Worker is
           access all Worker'Class;
        pragma Asynchronous (Any_Worker);

     private
        --  implementation removed
     end Common;

   We define an abstract tagged type Worker which is intended to be the
root type of the whole distributed objects hierarchy. Assign allows a
factory to specify a job to a worker and a way for the worker to signal
its employer the completion of this job. Any_Worker is a remote access
to class wide type (RACW). In other words, it is a reference to a
distributed object of any derived type from Worker class. Note that the
two remote access types (Any_Worker and Notify) are declared as
asynchronous. Therefore, any override of Assign will be executed
asynchronously. To be asynchronous, an object of type Notify has to be a
reference to an asynchronous procedure.

   NewWorker is derived from type Worker and Assign is overridden.


     with Common, Storage; use Common, Storage;
     package NewWorkers is
        pragma Remote_Types;

        type NewWorker is new Worker with private;

        procedure Assign
          (W : access NewWorker;
           Q : Integer;
           N : Notify);
     private
        --  implementation removed
     end NewWorkers;

   The following code shows how to derive a second generation of workers
NewNewWorker from the first generation NewWorker. As mentioned above,
this RT package can be duplicated on several partitions to produce
several types of workers and also several remote workers.


     with Common, Storage, NewWorkers; use Common, Storage, NewWorkers;
     package NewNewWorkers is
        pragma Remote_Types;

        type NewNewWorker is new NewWorker with private;

        procedure Assign
          (W : access NewNewWorker;
           Q : Integer;
           N : Notify);
     private
        --  implementation removed
     end NewNewWorkers;

   In the following code, we define a unique place where workers wait
for jobs. WorkerCity is a Remote_Call_Interface package with services to
hire and free workers. Unlike Remote_Types packages,
Remote_Call_Interface packages cannot be duplicated, and are assigned to
one specific partition.


     with Common; use Common;
     package WorkerCity is
        pragma Remote_Call_Interface;

        procedure Insert (W : in  Any_Worker);
        procedure Remove (W : out Any_Worker);
     end WorkerCity;

   In order to use even more DSA features, Factory is defined as a
generic RCI package (see sample above). Any instantiation defines a new
factory (see sample above). To be RCI, this instantiation has to be
categorized once again.


     with Storage; use Storage;
     generic
     package Factory is
        pragma Remote_Call_Interface;

        procedure Notify (Q : Integer);
        pragma Asynchronous (Notify);
     end Factory;


     with Factory;
     package NewFactory is new Factory;
     pragma Remote_Call_Interface (NewFactory);

8.4 A small example of a DSA application
========================================

In this section we will write a very simple client-server application
using PolyORB DSA. The server will provide a `Remote Call Interface'
composed of a single `Echo_String' function that will take a String and
return it to the caller.

   Here is the code for the server:

   `server.ads':


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --                               S E R V E R                                --
     --                                                                          --
     --                                 S p e c                                  --
     --                                                                          --
     --         Copyright (C) 2011-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     package Server is
        pragma Remote_Call_Interface;
        function Echo_String (S : String) return String;
     end Server;

   `server.adb':


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --                               S E R V E R                                --
     --                                                                          --
     --                                 B o d y                                  --
     --                                                                          --
     --         Copyright (C) 2011-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     package body Server is

        function Echo_String (S : String) return String is
        begin
           return S;
        end Echo_String;

     end Server;

   And here is the code for the client:

   `client.adb':


     ------------------------------------------------------------------------------
     --                                                                          --
     --                           POLYORB COMPONENTS                             --
     --                                                                          --
     --                               C L I E N T                                --
     --                                                                          --
     --                                 B o d y                                  --
     --                                                                          --
     --         Copyright (C) 2011-2012, Free Software Foundation, Inc.          --
     --                                                                          --
     -- This is free software;  you can redistribute it  and/or modify it  under --
     -- terms of the  GNU General Public License as published  by the Free Soft- --
     -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
     -- sion.  This software is distributed in the hope  that it will be useful, --
     -- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
     -- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public --
     -- License for  more details.                                               --
     --                                                                          --
     -- You should have received a copy of the GNU General Public License and    --
     -- a copy of the GCC Runtime Library Exception along with this program;     --
     -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
     -- <http://www.gnu.org/licenses/>.                                          --
     --                                                                          --
     --                  PolyORB is maintained by AdaCore                        --
     --                     (email: sales@adacore.com)                           --
     --                                                                          --
     ------------------------------------------------------------------------------

     with Ada.Exceptions;
     with Ada.Text_IO; use Ada.Text_IO;
     with Server;

     procedure Client is
     begin
        Put_Line ("The client has started!");
        Put ("Thus spake my server upon me:");
        Put_Line (Server.Echo_String ("Hi!"));
     exception
        when E : others =>
           Put_Line ("Got " & Ada.Exceptions.Exception_Information (E));
     end Client;

For more details about the Distributed Systems Annex, see the Ada
Reference Manual `[ISO06]'.

8.5 Building a DSA application with PolyORB
===========================================

This section describes how to build a complete distributed Ada
application using the PolyORB implementation of the DSA.

8.5.1 Introduction to PolyORB/DSA
---------------------------------

A distributed Ada application comprises a number of partitions which
can be executed concurrently on the same machine or, and this is the
interesting part, can be distributed on a network of machines.  The way
in which partitions communicate is described in Annex E of the Ada
Reference Manual.

   A partition is a set of compilation units that are linked together to
produce an executable binary. A distributed program comprises two or
more communicating partitions.

   The Distributed Systems Annex (DSA) does not describe how a
distributed application should be configured. It is up to the user to
define what are the partitions in his program and on which machines
they should be executed.

   The tool po_gnatdist and its configuration language allows the user
to partition his program and to specify the machines on which the
individual partitions are to execute.

   po_gnatdist reads a configuration file (whose syntax is described in
section *note The Configuration Language::) and builds several
executables, one for each partition. It also takes care of launching the
different partitions (default) with parameters that can be specific to
each partition.

8.5.2 How to Configure a Distributed Application
------------------------------------------------

   * Write a non-distributed Ada application, to get familiar with the
     PolyORB environment. Use the categorization pragmas to specify the
     packages that can be called remotely.

   * When this non-distributed application is working, write a
     configuration file that maps the user categorized packages onto
     specific partitions. This concerns particularly remote call
     interface and remote types packages.  Specify the main procedure
     of the distributed application (see *note Partition Attribute
     Main::).

   * Type `po_gnatdist <configuration-file>'.

   * Start the distributed application by invoking the start-up shell
     script or default Ada program (depending on the Starter option,
     see *note Pragma Starter::).


8.5.3 Gnatdist Command Line Options
-----------------------------------


     po_gnatdist [switches] configuration-file [list-of-partitions]

   The switches of po_gnatdist are, for the time being, exactly the same
as those of gnatmake, with the addition of -PCS, which allows the user
to override the default selection of distribution runtime library
(PCS). By default po_gnatdist outputs a configuration report and the
actions performed. The switch -n allows po_gnatdist to skip the first
stage of recompilation of the non-distributed application.

   The names of all configuration files must have the suffix .cfg.
There may be several configuration files for the same distributed
application, as the user may want to use different distributed
configurations depending on load and other characteristics of the
computing environment.

   If a list of partitions is provided on the command line of the
po_gnatdist command, only these partitions will be built. In the
following configuration example, the user can type :


     po_gnatdist <configuration> <partition_2> <partition_3>

8.5.4 The Configuration Language
--------------------------------

The configuration language is Ada-like. As the capabilities of PolyORB
will evolve, so will this configuration language. Most of the attributes
and pragmas can be overridden at run-time by command line arguments or
environment variables.

8.5.4.1 Language Keywords
.........................

All the Ada keywords are reserved keywords of the configuration
language. po_gnatdist generates full Ada code in order to build the
different executables. To avoid naming conflicts between Ada and the
configuration language, all the Ada keywords have been reserved even if
they are not used in the configuration language.

   In addition, the following keywords are defined:
   * configuration to encapsulate a configuration

   * partition that is a predefined type to declare partitions

8.5.4.2 Pragmas and Representation Clauses
..........................................

It is possible to modify the default behavior of the configuration via
a pragma definition.


     PRAGMA ::=
        pragma PRAGMA_NAME [(PRAGMA_ARGUMENTS)];

   It is also possible to modify the default behavior of all the
partitions via an attribute definition clause applied to the predefined
type Partition.


     REPRESENTATION_CLAUSE ::=
        for Partition'ATTRIBUTE_NAME use ATTRIBUTE_ARGUMENTS;

   It is also possible to modify the default behavior of a given
partition via an attribute definition clause applied to the partition
itself.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'ATTRIBUTE_NAME use ATTRIBUTE_ARGUMENTS;

   When an attribute definition clause is applied to a given object of a
predefined type, this overrides any attribute definition of the
predefined type. In the next sections, attributes apply to a given
object rather than to the predefined type.

8.5.4.3 Configuration Declaration
.................................

The distribution of one or several Ada programs is described by a single
configuration unit. This configuration unit has a specification part and
an optional body part. A configuration unit is declared as an Ada
procedure would be. The keyword configuration is reserved for this
purpose.


     CONFIGURATION_UNIT ::=
        configuration IDENTIFIER is
           DECLARATIVE_PART
        [begin
           SEQUENCE_OF_STATEMENTS]
        end [IDENTIFIER];

8.5.4.4 Partition Declaration
.............................

In the declarative part, the user declares his partitions and can change
their default behavior. po_gnatdist provides a predefined type
Partition. The user can declare a list of partitions and can also
initialize these partitions with an initial list of Ada units.


     DECLARATIVE_PART ::= {DECLARATIVE_ITEM}

     DECLARATIVE_ITEM ::=
        PARTITION_DECLARATION
      | REPRESENTATION_CLAUSE
      | SUBPROGRAM_DECLARATION
      | PRAGMA

     SUBPROGRAM_DECLARATION ::=
        MAIN_PROCEDURE_DECLARATION
      | PROCEDURE_DECLARATION
      | FUNCTION_DECLARATION

     PARTITION_DECLARATION ::=
        DEFINING_IDENTIFIER_LIST : Partition
           [:= ENUMERATION_OF_ADA_UNITS];

     DEFINING_IDENTIFIER_LIST ::=
        DEFINING_IDENTIFIER {, DEFINING_IDENTIFIER}

     STATEMENT ::=
        IDENTIFIER := ENUMERATION_OF_ADA_UNITS;

     SEQUENCE_OF_STATEMENTS ::=
        STATEMENT {STATEMENT}

   Once declared, a partition is an empty list of Ada units. The
operator ":=" adds the Ada units list on the right side to the current
list of Ada units that are already mapped to the partition. This is a
non-destructive operation. Whether a unit is a relevant Ada unit or not
is checked later on by the back-end of po_gnatdist. These assignments
can occur in the declarative part as well as in the body part.


     ENUMERATION_OF_ADA_UNITS ::= ({ADA_UNIT {, ADA_UNIT}});

8.5.4.5 Location Declaration
............................

There are several kinds of location in the configuration language. We
shall present them in the next subsections, but here is a short
overview of these locations:

   * Boot_Location defines the network locations to use to communicate
     with the the boot server during the boot phase

   * Self_Location defines the network locations to use by others to
     communicate with the current partition

   * Data_Location defines the data storage location used by the
     current partition to map its shared passive units


   A location is composed of a support name and a specific data for this
support. For instance, a network location is composed of a protocol name
like tcp and a protocol data like <machine>:<port>. A storage location
is composed of a storage support name like dfs (for Distributed File
System) and a storage support data like a directory /dfs/glade.


     LOCATION      ::= ([Support_Name =>] STRING_LITERAL,
                        [Support_Data =>] STRING_LITERAL)

     LOCATION_LIST ::= (LOCATION [,LOCATION)])

   Note that a location may have an undefined or incomplete support
data. In this case, the support is free to compute a support data. For
instance, ("tcp", "") specifies that the protocol is used but that the
protocol data <machine>:<port> is to be determined by the protocol
itself.

   A location or a list of locations can be can be concatenated into a
single string to be used as a command line option or an environment
variable (see *note Partition Runtime Parameters::).

   If a partition wants to communicate with another partition once the
location list of the latter is known, the caller will use the first
location of the callee whose protocol is locally available. For
instance, if a callee exports three locations ("N1", "D1"), ("N2", "D2")
and ("N3", "D3"), a caller with protocols N2 and N3 locally available
will try to communicate with the callee using the protocol of name N2
and of specific data D2.

8.5.4.6 Partition Attribute Main
................................

Basically, the distributed system annex (DSA) helps the user in building
a distributed application from a non-distributed application (Of course,
this is not the only possible model offered by DSA). The user can
design, implement and test his application in a non-distributed
environment, and then should be able to switch from the non-distributed
case to a distributed case. As mentioned before, this two-phase design
approach has several advantages.

   In a non-distributed case, the user executes only one main executable
possibly with a name corresponding to the main unit name of his
application. With po_gnatdist, in a distributed case, a main executable
with a name corresponding to the main unit name is responsible for
starting the entire distributed application. Therefore, the user can
start his application the same way he used to do in the non-distributed
case.

   For this reason, the configuration language provides a way to declare
the main procedure of the non-distributed application.


     MAIN_PROCEDURE_IDENTIFIER ::=
       ADA_UNIT
     MAIN_PROCEDURE_DECLARATION ::=
        procedure MAIN_PROCEDURE_IDENTIFIER is in PARTITION_IDENTIFIER;

   In this case, the partition in which the main procedure has been
mapped is called the main partition. It includes in its code a call to
this main procedure. The main partition has an additional specific role,
because the boot server is located on it (see *note PolyORB PCS
Internals::).

   The main procedures for the other partitions have a null body.
However, the user can also modify this behavior by providing an
alternate main procedure. To do this, an alternate main subprogram has
to be declared and assigned to the partition Main attribute.


     PROCEDURE_DECLARATION ::=
        procedure PROCEDURE_IDENTIFIER;

     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Main use PROCEDURE_IDENTIFIER;

8.5.4.7 Pragma Starter
......................

As a default, the main executable is a full Ada starter procedure. That
means that it launches all the other partitions from an Ada program. The
pragma Starter allows the user to ask for one starter or another. When
the partition host is not statically defined (see *note Partition
Attribute Host::), the starter subprogram will ask for it interactively
when it is executed.


     CONVENTION_LITERAL ::= Ada   |
                            Shell |
                            None

     PRAGMA ::=
        pragma Starter ([Convention =>] CONVENTION_LITERAL);

   * The default method consists in launching partitions from the main
     partition Ada subprogram using a remote shell (see below).

   * The user may ask for a Shell script that starts the different
     partitions one at a time on the appropriate remote machines, using
     a remote shell. As the Ada starter, the Shell script starter ask
     for partition hosts interactively when a partition host is not
     already defined. Having a textual shell script allows the user to
     edit it and to modify it easily.

   * The user may ask for a None starter. In this case, it is up to the
     user to launch the different partitions.


8.5.4.8 Pragma Remote_Shell
...........................

When pragma Starter is Ada or Shell, the main partition launches the
other partitions. The remote shell used as a default is determined
during PolyORB configuration and installation. It is either rsh, remsh
or the argument passed to -with-rshcmd=[ARG]. The pragma Remote_Shell
allows the user to override the default.


     PRAGMA ::=
        pragma Remote_Shell
          ([Command =>] STRING_LITERAL,
           [Options =>] STRING_LITERAL);

   The Command parameter indicates the name of the remote shell command
name and the Options parameter corresponds to the additional flags to
pass to the remote shell command.

8.5.4.9 Pragma Name_Server
..........................


     NAME_SERVER_LITERAL ::= Embedded   |
                            Standalone

     PRAGMA ::=
        pragma Name_Server ([Name_Server_Kind =>] NAME_SERVER_LITERAL);

   By default, partitions in a PolyORB/DSA application rely on an
external, stand-alone name server launched by the user, and whose
location is retrieved from runtime configuration.

   A pragma Name_Server with parameter Embedded can be used to request
the PCS to instead set up a name server within the main partition. If
the Ada starter is used, the location of the name server is passed
automatically to slave partitions.

8.5.4.10 Pragma Boot_Location
.............................

When a partition starts executing, one of the first steps consists in a
connection to the boot server. This pragma provides one or more
locations in order to get a connection with the boot server.


     PRAGMA ::=
        PRAGMA_WITH_NAME_AND_DATA
      | PRAGMA_WITH_LOCATION
      | PRAGMA_WITH_LOCATION_LIST

     PRAGMA_WITH_NAME_AND_DATA ::=
        pragma Boot_Location
          ([Protocol_Name =>] STRING_LITERAL,
           [Protocol_Data =>] STRING_LITERAL);

     PRAGMA_WITH_LOCATION ::=
        pragma Boot_Location ([Location =>] LOCATION);

     PRAGMA_WITH_LOCATION_LIST ::=
        pragma Boot_Location ([Locations =>] LOCATION_LIST);

   This boot server location can be concatenated into a single string
to be used as a command line option or an environment variable (see
*note Partition Runtime Parameters::).

   Note: pragma Boot_Server is now obsolete. It is recommended to use
pragma Boot_Location. This wording is more consistent with the rest of
the configuration language (see Self_Location *note Partition Option
self_location:: and Data_Location *note Partition Option
data_location::).

8.5.4.11 Partition Attribute Self_Location
..........................................

Except for the boot partition on which the boot server is located, a
partition is reachable through a dynamically computed location (for
instance, the partition looks for a free port when the protocol is
tcp). The user may want such a partition to be reachable from a given
location, especially if the user wants to make this partition a boot
mirror. To do so, he can force the partition location with self_location
feature.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Self_Location use LOCATION;
      | for PARTITION_IDENTIFIER'Self_Location use LOCATION_LIST;

   If the attribute definition clause applies to the predefined type
Partition, the locations have to be incomplete. Otherwise, all the
partitions would be reachable through the same locations, which is
definitively not recommended.

   When an attribute self_location definition clause applies to a given
partition, the protocol units needed for this partition are linked in
the executable. By default, when the self_location attribute is not
redefined, the default protocol used by the partition and loaded in its
executable is the tcp protocol.

8.5.4.12 Partition Attribute Passive
....................................

By default, a partition is an active partition. This attribute allows to
define a passive partition. In this case, po_gnatdist checks that only
shared passive units are mapped on the partition. As this partition
cannot register itself, its location is hard-coded in all the partitions
that depend on its shared passive units.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Passive use BOOLEAN_LITERAL;

8.5.4.13 Partition Attribute Data_Location
..........................................

Shared passive units can be mapped on passive or active partitions. In
both cases, it is possible to choose the data storage support and to
configure it with the specific data of a location.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Data_Location use LOCATION;
      | for PARTITION_IDENTIFIER'Data_Location use LOCATION_LIST;

   When an attribute data_location definition clause applies to a given
partition, the data storage support units needed for this partition are
linked in the executable. By default, when the data_location attribute
is not redefined, the default storage support used by the partition and
loaded in its executable is the dfs support. dfs, Distributed File
System, is a storage support available as soon as files can be shared
between partitions.

   It is not possible to map the different shared passive units of a
given partition on different data storage locations. PolyORB requires
all the shared passive units of a given partition to be mapped on the
same storage support. When the attribute data_location applied to a
partition is a list of locations, all the storage support units needed
for this partition are linked in the executable. By default, only the
first one is activated. The user can choose to change the activated
support by another one specified in the location list. This can be done
using the partition option data_location (see *note Partition Option
data_location::).

   As passive partitions cannot be activated, it is not possible to
provide a location list as a data_location attribute. It is not
possible to change dynamically its location either.

8.5.4.14 Partition Attribute Allow_Light_PCS
............................................

On some circumstances, po_gnatdist can detect that a partition does not
need the full PCS functionalities. This occurs in particular when the
partition does use any task, any RCI unit or any RACW object. Therefore,
the partition does not receive any message that is not a reply to a
previous request. In this case, the PCS does not drag in the tasking
library and a light PCS is linked in the partition executable.  This
specific configuration is automatically determined by po_gnatdist with
the ALI file information.

   This optimization can be inappropriate especially when the user
wants to use the "Distributed Shared Memory" storage support which runs
Li and Hudak's algorithm. In this case, messages are exchanged without
being replies to previously sent requests and the normal PCS should be
linked instead of the light one. Note also that po_gnatdist cannot know
for sure that the DSM storage support assigned at configuration time is
used at run-time. The user can configure this optimization with the
following attribute.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Allow_Light_PCS use BOOLEAN_LITERAL;

8.5.4.15 Pragma Priority
........................

It might be necessary for real-time applications to get control over the
priority at which a remote procedure call is executed. By default, the
PCS sends the priority of the client to the server which sets the
priority of an anonymous task to this value. The pragma Priority allows
to decide which priority policy should apply in the distributed
application.


     PRIORITY_POLICY_LITERAL ::= Server_Declared
                               | Client_Propagated

     PRAGMA ::=
        pragma Priority ([Policy =>] PRIORITY_POLICY_LITERAL);

   * The default policy Client_Propagated consists in propagating the
     client priority to the server.

   * The policy Server_Declared consists in executing the remote
     procedure call at a priority specific to the partition. This
     priority can be set using the partition attribute Priority.


8.5.4.16 Partition Attribute Priority
.....................................

This attribute allows to set the priority at which level a remote
procedure call is executed on a server when the priority policy is
Server_Declared. By default, the default priority of the anonymous task
is the default task priority.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Priority use INTEGER_LITERAL;

8.5.4.17 Partition Attribute Host
.................................

Logical nodes (or partitions) can be mapped onto physical nodes. The
host-name can be either a static or dynamic value. In case of a static
value, the expression is a string literal. In case of a dynamic value,
the representation clause argument is a function that accepts a string
as parameter and that returns a string value. When the function is
called, the partition name is passed as parameter and the host-name is
returned.


     FUNCTION_DECLARATION ::=
        function FUNCTION_IDENTIFIER
          (PARAMETER_IDENTIFIER : [in] String)
           return String;

     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Host use STRING_LITERAL;
      | for PARTITION_IDENTIFIER'Host use FUNCTION_IDENTIFIER;

   The signature of the function must be the following : it takes a
string parameter which corresponds to a partition name. It returns a
string parameter which corresponds to the host-name. The function that
returns the host-name can be an Ada function (default) or a shell
script. A pragma Import is used to import a function defined in Ada or
in Shell (see *note Pragma Import::).

   This function is called on the main partition by the PCS to launch a
given partition on a given logical node. In case of load balancing, the
function can return the most appropriate among a set of hosts.

8.5.4.18 Pragma Import
......................

Two kinds of subprograms are allowed in the configuration language. A
main procedure is used as a partition Main attribute and a function is
used as a partition Host attribute.


     PROCEDURE_DECLARATION ::=
          procedure PROCEDURE_IDENTIFIER;
     FUNCTION_DECLARATION ::=
          function FUNCTION_IDENTIFIER
             (PARAMETER_IDENTIFIER : [in] String)
              return String;

   The function can be an Ada function (default) or a shell script. To
import a shell script, the pragma Import must be used:


     PRAGMA ::=
        pragma Import
           ([Entity        =>] FUNCTION_IDENTIFIER,
            [Convention    =>] CONVENTION_LITERAL,
            [External_Name =>] STRING_LITERAL);

     pragma Import (Best_Node, Shell, "best-node");

   In this case, the PCS invokes the shell script with the partition
name as a command line argument. The shell script is supposed to return
the partition host-name (see *note Partition Attribute Host::).

8.5.4.19 Partition Attribute Directory
......................................

Directory allows the user to specify in which directory the partition
executable is stored. This can be useful in heterogeneous systems when
the user wants to store executables for the same target in a given
directory. Specifying the directory is also useful if the partition
executable is not directly visible from the user environment. For
instance, when a remote command like rsh is invoked, the executable
directory has to be present in the user path. If the Directory
attribute has been specified, the executable full name is used.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Directory use STRING_LITERAL;

8.5.4.20 Partition Attribute Command_Line
.........................................

The user may want to pass arguments on the command line of a partition.
However, when a partition is launched automatically by the main
partition, the partition command line includes only PolyORB arguments.
To add arguments on the command line, the user can take advantage of
the following attribute.


     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Command_Line use STRING_LITERAL;

8.5.4.21 Partition Attribute Environment_Variables
..................................................

The attribute Environment_Variables allows the user to specify a list of
environment variables that should be passed from the main partition to
slave partitions when using a generated (shell or Ada) launcher.

   This attribute can be applied to all partitions by defining it for
the predefined type Partition, or to a specific partition. Note that in
the latter case, the list does not replace the default one but instead
complements it (i.e. variables specified for Partition are passed in
addition to the partition specific ones).

   Use of this features requires that remote nodes provide the POSIX
env(1) command.


     STRING_LITERAL_LIST ::=
        STRING_LITERAL
        | STRING_LITERAL, STRING_LITERAL_LIST

     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Environment_Variables use (STRING_LITERAL_LIST);

8.5.4.22 Partition Attribute Termination
........................................

The Ada Reference Manual does not provide any specific rule to handle
global termination of a distributed application (see *note Abortion and
Termination::).

   In PolyORB/DSA, by default, a set of partitions terminates when each
partition can terminate and when no message remains to be delivered. A
distributed algorithm that checks for this global condition is activated
periodically by the main boot server.


     TERMINATION_LITERAL ::= Global_Termination |
                             Local_Termination  |
                             Deferred_Termination

     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Termination use TERMINATION_LITERAL;

   * When a partition is configured with the global termination policy,
     it terminates as soon as the main boot server sends a signal to do
     so. The main boot server checks periodically whether the
     application can terminate. When all partitions are ready to
     terminate, the main boot server sends to each partition a
     termination request. The global termination policy is the default
     policy.

   * The deferred termination policy is very similar to the global
     termination. The only difference is that when a partition with a
     deferred termination policy receives a termination request, it just
     ignores it. This policy allows a partition to run forever without
     preventing a set of partitions from terminating.

   * When a partition is configured with the local termination policy,
     it terminates as soon as the classical Ada termination is detected
     by the partition. It means that this partition does not wait for
     the termination request of the main boot server.


8.5.4.23 Partition Attribute Reconnection
.........................................

When no RCI package is configured on a partition, such a partition can
be launched several times without any problem. When one or more RCI
packages are configured on a partition, such a partition cannot be
launched more than once. If this partition were to be launched
repeatedly, it would not be possible to decide which partition instance
should execute a remote procedure call.

   When a partition crashes or is stopped, one may want to restart this
partition and possibly restore its state - with Shared_Passive packages,
for instance. In such a situation, the partition is already known to
other partitions and possibly marked as a dead partition. Several
policies can be selected:


     RECONNECTION_LITERAL ::= Reject_On_Restart  |
                               Fail_Until_Restart |
                               Block_Until_Restart

     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Reconnection use RECONNECTION_LITERAL;

   * When this partition is configured with the Reject_On_Restart
     reconnection policy, the dead partition is kept dead and any
     attempt to restart it fails. Any remote call to a subprogram
     located on this partition results in a Communication_Error
     exception. The Reject_On_Restart policy is the default policy.

   * When this partition is configured with the Fail_Until_Restart
     reconnection policy, the dead partition can be restarted. Any
     remote call to a subprogram located on this partition results in
     an exception Communication_Error as long as this partition has not
     been restarted. As soon as the partition is restarted, remote
     calls to this partition are executed normally.

   * When this partition is configured with the Block_Until_Restart
     reconnection policy, the dead partition partition can be
     restarted. Any remote call to a subprogram located on this
     partition is suspended until the partition is restarted. As soon
     as the partition is restarted, remote calls to this partition are
     executed normally. The suspended remote procedure calls to this
     partition are resumed.


8.5.4.24 Pragma Version
.......................

A library unit is consistent if the same version of its declaration is
used throughout (see *note Consistency and Elaboration::). It can be
useful to deactivate these checks, especially when the user wants to be
able to update a server without updating a client.


     PRAGMA ::=
        pragma Version ([Check =>] BOOLEAN_LITERAL);

8.5.4.25 Partition Attribute Task_Pool
......................................

When multiple remote subprogram calls occur on the same partition, they
are handled by several anonymous tasks. These tasks can be allocated
dynamically or re-used from a pool of (preallocated) tasks. When a
remote subprogram call is completed, the anonymous task can be
deallocated or queued in a pool in order to be re-used for further
remote subprogram calls. The number of tasks in the anonymous tasks pool
can be configured by means of three independent parameters.

   * The task pool minimum size indicates the number of anonymous tasks
     preallocated and always available in the PCS. Preallocating
     anonymous tasks can be useful in real-time systems to prevent task
     dynamic allocation.

   * The task pool high size is a ceiling. When a remote subprogram
     call is completed, its anonymous task is deallocated if the number
     of tasks already in the pool is greater than the ceiling. If not,
     then the task is queued in the pool.

   * The task pool maximum size indicates the maximum number of
     anonymous tasks in the PCS. In other words, it provides a way to
     limit the number of remote calls in the PCS. When a RPC request is
     received, if the number of active remote calls is greater than the
     task pool maximum size, then the request is kept pending until an
     anonymous task completes its own remote call and becomes available.



     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'Task_Pool use TASK_POOL_SIZE_ARRAY;

     TASK_POOL_SIZE_ARRAY ::=
       (NATURAL_LITERAL,  -  Task Pool Minimum Size
        NATURAL_LITERAL,  -  Task Pool High Size
        NATURAL_LITERAL); -  Task Pool Maximum Size

   In order to have only one active remote call at a  time, the task
pool configuration is declared as follows:


     for Partition'Task_Pool use (0, 0, 1);

8.5.4.26 Partition Attribute ORB_Tasking_Policy
...............................................

By default, the Thread_Pool ORB tasking policy is used for all
partitions.  This attribute allows selection of an alternate policy
among those provided by PolyORB (see *note PolyORB ORB Tasking
policies::) for each partition.

     ORB_TASKING_POLICY_LITERAL ::= Thread_Pool        |
                                    Thread_Per_Session |
                                    Thread_Per_Request

     REPRESENTATION_CLAUSE ::=
        for PARTITION_IDENTIFIER'ORB_Tasking_Policy use ORB_TASKING_POLICY_LITERAL;

   Note: *note Partition Attribute Task_Pool:: has no effect when
another policy than Thread_Pool is activated.

8.5.4.27 A Complete Example
...........................

Almost every keyword and construct defined in the configuration language
has been used in the following sample configuration file.


     configuration MyConfig is

       Partition_1 : Partition := ();
       procedure Master_Procedure is in Partition_1;

       Partition_2, Partition_3 : Partition;

       for Partition_2'Host use "foo.bar.com";

       function Best_Node (Partition_Name : String) return String;
       pragma Import (Shell, Best_Node, "best-node");
       for Partition_3'Host use Best_Node;

       Partition_4 : Partition := (RCI_B5);

       for Partition_1'Directory use "/usr/you/test/bin";
       for Partition'Directory use "bin";

       procedure Another_Main;
       for Partition_3'Main use Another_Main;

       for Partition_3'Reconnection use Block_Until_Restart;
       for Partition_4'Command_Line use "-v";
       for Partition_4'Termination use Local_Termination;

       pragma Starter (Convention => Ada);

       pragma Boot_Server
         (Protocol_Name => "tcp",
          Protocol_Data => "`hostname`:`unused-port`");

       pragma Version (False);

     begin
        Partition_2 := (RCI_B2, RCI_B4, Normal);
        Partition_3 := (RCI_B3);
     end MyConfig;

  1. Line 01 Typically, after having created the following
     configuration file the user types:


          po_gnatdist myconfig.cfg

     If the user wants to build only some partitions then he will list
     the partitions to build on the po_gnatdist command line as follows:


          po_gnatdist myconfig.cfg partition_2 partition_3

     The name of the file prefix must be the same as the name of the
     configuration unit, in this example myconfig.cfg. The file suffix
     must be cfg. For a given distributed application the user can have
     as many different configuration files as desired.

  2. Line 04 Partition 1 contains no RCI package. However, it will
     contain the main procedure of the distributed application, called
     Master_Procedure in this example. If the line procedure
     Master_Procedure is in Partition_1; was missing, Partition 1 would
     be completely empty. This is forbidden, because a partition has to
     contain at least one library unit.

     po_gnatdist produces an executable with the name of
     Master_Procedure which will start the various partitions on their
     host machines in the background. The main partition is launched in
     foreground. Note that by killing this main procedure the whole
     distributed application is terminated.

  3. Line 08 Specify the host on which to run partition 2.

  4. Line 12 Use the value returned by a program to figure out at
     execution time the name of the host on which partition 3 should
     execute.  For instance, execute the shell script best-node which
     takes the partition name as parameter and returns a string giving
     the name of the machine on which partition_3 should be launched.

  5. Line 14 Partition 4 contains one RCI package RCI_B5 No host is
     specified for this partition. The startup script will ask for it
     interactively when it is executed.

  6. Line 16 Specify the directory in which the executable of partition
     partition_1 will be stored.

  7. Line 17 Specify the directory in which all the partition
     executables will be stored (except partition_1, see *note Pragmas
     and Representation Clauses::). Default is the current directory.

  8. Line 20 Specify the partition main subprogram to use in a given
     partition.

  9. Line 22 Specify a reconnection policy in case of a crash of
     Partition_3. Any attempt to reconnect to Partition_3 when this
     partition is dead will be blocked until Partition_3 restarts. By
     default, any restart is rejected (Reject_On_Restart). Another
     policy is to raise Communication_Error on any reconnection attempt
     until Partition_3 has been restarted.

 10. Line 23 Specify additional arguments to pass on the command line
     when a given partition is launched.

 11. Line 24 Specify a termination mechanism for partition_4. The
     default is to compute a global distributed termination. When
     Local_Termination is specified a partition terminates as soon as
     local termination is detected (standard Ada termination).

 12. Line 26 Specify the kind of startup method the user wants. There
     are 3 possibilities: Shell, Ada and None. Specifying Shell builds
     a shell script. All the partitions will be launched from a shell
     script.  If Ada is chosen, then the main Ada procedure itself is
     used to launch the various partitions. If method None is chosen,
     then no launch method is used and the user must start each
     partition manually.

     If no starter is given, then an Ada starter will be used.

     In this example, Partition_2, Partitions_3 and Partition_4 will be
     started from Partition_1 (ie from the Ada procedure
     Master_Procedure).

 13. Line 30 Specify the use of a particular boot server.

 14. Line 32 It is a bounded error to elaborate a partition of a
     distributed program that contains a compilation unit that depends
     on a different version of the declaration of an RCI library unit
     than the one included in the partition to which the RCI library
     unit was assigned. When the pragma Version is set to False, no
     consistency check is performed.

 15. Line 34 The configuration body is optional. The user may have
     fully described his configuration in the declaration part.

 16. Line 35 Partition 2 contains two RCI packages RCI_B2 and RCI_B4
     and a normal package. A normal package is not categorized.

 17. Line 36 Partition 3 contains one RCI package RCI_B3


8.5.5 Partition Runtime Parameters
----------------------------------

You can adjust some parameters of your DSA applications using the
PolyORB configuration file, `polyorb.conf'. The parameters relevant to
the Ada Distributed Systems Annex are specified in the `[dsa]' section.

   See *note Run-time configuration:: for complete documentation of
PolyORB's runtime configuration facilities.

`name_service = [IOR/corbaloc]'
     You can set this parameter instead of the environment variable
     `POLYORB_DSA_NAME_SERVICE'.  Though if you use a Starter, ensure
     that this parameter is set for all the partitions, as this is not
     done automatically as for the `POLYORB_DSA_NAME_SERVICE'
     environment variable.

`max_failed_requests = [integer]'
     Each partition will attempt a given number of requests to the name
     server before failing. This allows some time for every partition
     to register in the name server.

`delay_between_failed_requests = [duration in milliseconds]'
     As above, only this specifies the delay between requests.

`termination_initiator = [true/false]'
     Is this partition a termination initiator.

`termination_policy = [global_termination/deferred_termination/local_termination]'
     The termination policy for this partition.

`tm_time_between_waves = [duration in milliseconds]'
     The delay between termination waves.

`tm_time_before_start = [duration in milliseconds]'
     The delay before the termination manager starts sending waves.

`detach = [true/false]'
     If true, the partition will be detached.

`rsh_options = [string]'
     Options passed to the rsh command when using the module
     polyorb.dsa_p-remote_launch

`rsh_command = [string]'
     Which command should the module polyorb.dsa_p-remote_launch use to
     spawn remote programs.

8.5.6 Gnatdist Internals
------------------------

Here is what goes on in po_gnatdist when building a distributed
application:

   * Each compilation unit in the program is compiled into an object
     module (as for non distributed applications). This is achieved by
     calling gnatmake on the sources of the various partitions.

   * Stubs and skeletons are compiled into object modules (these are
     pieces of code that allow a partition running on machine A to
     communicate with a partition running on machine B). Several
     timestamp checks are performed to avoid useless code recompilation
     and stub generation.

   * po_gnatdist performs a number of consistency checks. For instance
     it checks that all packages marked as remote call interface (RCI)
     and shared passive (SP) are mapped onto partitions. It also checks
     that a RCI or SP package is mapped onto only one partition.

   * Finally, the executables for each partition in the program are
     created. The code to launch partitions is embedded in the main
     partition except if another option has been specified (see *note
     Pragma Starter::). In this case, a shell script (or nothing) is
     generated to start the partitions on the appropriate machines.
     This is specially useful when one wants to write client / server
     applications where the number of instances of the partition is
     unknown.


   All Gnatdist intermediate files (object files, etc) are stored under
a common directory named "dsa". The user may remove this whole
directory and its content when he does not intend to rebuild his
distributed applications.

8.5.7 PolyORB PCS Internals
---------------------------

This section provides notes on the PolyORB implementation of the DSA
PCS.  Some of these features are not configurable by the user.

8.5.7.1 Application Startup
...........................

A name server needs to be started prior to starting any application
partition. Once the name server is started, its location must be passed
to all partitions as the name_service runtime parameter in the [dsa]
section of the configuration. When using an Ada starter, it is
sufficient to pass the name server location to the starter, and it will
be propagated automatically to all partitions.

   Upon elaboration, each partition registers its RCI packages with the
name server. Once this is done, remote calls to RCI subprograms can
proceed.  Partitions cache the replies from the name server so that
during the course of normal execution, inter-partition calls only
involve the caller and callee partitions (not the name server).

   RCI units can then act as "clearinghouses" for other partitions to
exchange RACWs and set up dynamic communication paths.

8.5.7.2 Heterogeneous System
............................

The GNAT environment provides default stream attributes, except for
non-remote access types (see *note Transmitting Dynamic Structure:: and
*note Marshalling and Unmarshalling Operations::). The implementation of
the default attributes of predefined types can be found in
System.Stream_Attributes (s-stratt.adb).

   The PolyORB PCS provides alternative data representations by default
to ensure portability of the data stream across partitions executing on
heterogeneous architectures. Users may override these representation
aspects by configuring the protocol personality of their choice.

8.5.7.3 Allocating Partition Ids
................................

The Partition_ID is allocated dynamically, at run-time. Each partition
connects to a Partition ID Server which is located on the boot server
and asks for a free Partition_ID. The advantage of this approach is that
it supports easily client / server solution (client partitions may be
duplicated, they will obtain different Partition Ids). There is no need
to recompile or relink all the partitions when a new partition is added
to the system. The Partition_ID is not tied in any way to a specific
protocol or to a specific location.

8.5.7.4 Executing Concurrent Remote Calls
.........................................

When multiple remote subprogram calls occur on the same partition, they
are handled by several anonymous tasks. The number of tasks in the
anonymous tasks pool can be configured by three figures (see *note
Partition Attribute Task_Pool::). Therefore, the user may have to
synchronize global data in the Remote_Call_Interface or Remote_Types
unit to preserve concurrent access on data. If the user want to suppress
the multiple requests features, he can force the configuration of the
anonymous tasks pool to (0 | 1, 0 | 1, 1). That means that there will be
at most one anonymous task running at a time.

8.5.7.5 Priority Inheritance
............................

It is compiler-dependent whether the caller priority is preserved during
a remote procedure call. In fact, it can be unsafe to rely on
priorities, because two partitions may have different priority ranges
and policies. Nevertheless, PolyORB preserves the caller priority. This
priority is marshaled and unmarshaled during the remote procedure call
and the priority of the anonymous task on the server is set to the
caller priority.

   This default policy can be modified by using pragma Priority *note
Pragma Priority:: and partition attribute Priority *note Partition
Attribute Priority::.

8.5.7.6 Remote Call Abortion
............................

When a remote procedure call is aborted, PolyORB will abort the calling
task on the caller side. It will also try to abort the remote anonymous
task performing the remote call, unless runtime parameter
`abortable_rpcs' in section `[tasking]' is set False on the server.

8.6 Running a DSA application
=============================

By default `po_gnatdist' will use the Ada starter. So if you have not
specified `pragma Starter (None);' in the `po_gnatdist' configuration
file, you should have a starter in your build directory, named after
the main procedure defined in the configuration file.  In this case you
just have to run this program.

   If you don't want to use the Starter and have specified `pragma
Starter (None);' in your configuration file, then you should have, in
your Partition'Directory, one binary for each of your partitions.
You'll have to start each of these programs manually.

   In both cases you must specify a name server for your application.
You can use for example the one included in PolyORB: `po_cos_naming'.
When running this name server it will output its IOR URI named
`POLYORB_CORBA_NAME_SERVICE'.

   Just ensure that you set the global environment variable
`POLYORB_DSA_NAME_SERVICE' to an IOR URI referencing the running name
server. When using the `po_cos_naming' name server just set
`POLYORB_DSA_NAME_SERVICE' environment variable to the first value
output for `POLYORB_DSA_NAME_SERVICE' before launching each DSA
partition.

   Here is a small trace output that demonstrates the setup


     polyorb/examples/dsa/echo% ../../../tools/po_cos_naming/po_cos_naming&
     polyorb/examples/dsa/echo% POLYORB_CORBA_NAME_SERVICE=''....''

     polyorb/examples/dsa/echo% export POLYORB_DSA_NAME_SERVICE=''...''
     polyorb/examples/dsa/echo% ./client
     The client has started!
     Thus spake my server upon me:Hi!

9 MOMA
******

9.1 What you should know before Reading this section
====================================================

This section assumes that the reader is familiar with the JMS
specifications described in `[SUN99]'. MOMA is a thick adaptation of
the JMS specification to the Ada programming language, preserving most
of the JMS concepts.

9.2 Installing MOMA application personality
===========================================

Ensure PolyORB has been configured and then compiled with the MOMA
application personality. See *note Building an application with
PolyORB:: for more details on how to check installed personalities.

   To build the MOMA application personality, *note Installation::.

9.3 Package hierarchy
=====================

Packages installed in `$INSTALL_DIR/include/polyorb/moma' hold the MOMA
API. MOMA is built around two distinct sets of packages:

  1. `MOMA.*' hold the public MOMA library, all the constructs the user
     may use.

  2. `POLYORB.MOMA_P.*' hold the private MOMA library, these packages
     shall not be used when building your application.


10 Ada Web Server (AWS)
***********************

The documentation of this personality will appear in a future revision
of PolyORB.

11 GIOP
*******

11.1 Installing GIOP protocol personality
=========================================

Ensure PolyORB has been configured and then compiled with the GIOP
protocol personality. See *note Building an application with PolyORB::
for more details on how to check installed personalities.

   To enable configuration of the GIOP protocol personality, *note
Installation::.

11.2 GIOP Instances
===================

GIOP is a generic protocol that can be instantiated for multiple
transport stacks. PolyORB provides three different instances.

11.2.1 IIOP
-----------

Internet Inter-ORB Protocol (IIOP) is the default protocol defined by
the CORBA specifications. It is a TCP/IP, IPv4, based protocol that
supports the full semantics of CORBA requests.

11.2.2 SSLIOP
-------------

The SSLIOP protocol provides transport layer security for transmitted
requests.  Its provides encryption of GIOP requests.

   To build the SSLIOP, it is required to activate SSL-related features
when building PolyORB. See `--with-openssl' in *note Installation:: for
more details.

   Enabling security is completely transparent to a preexisting
application, it is also possible to phase in secure communications by
allowing incoming requests which are unsecured.

11.2.3 DIOP
-----------

Datagram Inter-ORB Protocol (DIOP) is a specialization of GIOP for the
UDP/IP protocol stack. It supports only asynchronous (`oneway')
requests.

   This protocol is specific to PolyORB. DIOP 1.0 is a mapping of GIOP
on top of UDP/IP. DIOP 1.0 uses GIOP 1.2 message format.

11.2.4 MIOP
-----------

Unreliable Multicast Inter-ORB Protocol (MIOP) `[OMG02b]' is a
specialization of GIOP for IP/multicast protocol stack. It supports
only asynchronous (`oneway') requests.

11.3 Configuring the GIOP personality
=====================================

The GIOP personality is configured using a configuration file. See
*note Using a configuration file:: for more details.

   Here is a summary of available parameters for each instance of GIOP.

11.3.1 Common configuration parameters
--------------------------------------

This section details configuration parameters common to all GIOP
instances.

     ###############################################################################
     # GIOP parameters
     #

     [giop]

     ###############################################################
     # Native code sets
     #
     # Available char data code sets:
     #   16#00010001#   ISO 8859-1:1987; Latin Alphabet No. 1
     #   16#05010001#   X/Open UTF-8; UCS Transformation Format 8 (UTF-8)
     #
     # Available wchar data code sets:
     #   16#00010100#   ISO/IEC 10646-1:1993; UCS-2, Level 1
     #   16#00010109#   ISO/IEC 10646-1:1993;
     #                                UTF-16, UCS Transformation Format 16-bit form
     #
     #giop.native_char_code_set=16#00010001#
     #giop.native_wchar_code_set=16#00010100#
     #
     # The following parameters force the inclusion of fallback code sets
     # as supported conversion code sets. This is required to enable
     # interoperability with ORBs whose code sets negotiation support is
     # broken. See PolyORB's Users Guide for additional information.
     #
     #giop.add_char_fallback_code_set=false
     #giop.add_wchar_fallback_code_set=false

11.3.2 IIOP Configuration Parameters
------------------------------------


     ###############################################################################
     # IIOP parameters
     #

     [iiop]

     ###############################################################
     # IIOP Global Settings

     # Preference level for IIOP
     #polyorb.binding_data.iiop.preference=0

     # IIOP's default address
     #polyorb.protocols.iiop.default_addr=127.0.0.1

     # IIOP's default port
     #polyorb.protocols.iiop.default_port=2809

     # IIOP's alternate addresses
     #polyorb.protocols.iiop.alternate_listen_addresses=127.0.0.1:2810 127.0.0.1:2820

     # Default GIOP/IIOP Version
     #polyorb.protocols.iiop.giop.default_version.major=1
     #polyorb.protocols.iiop.giop.default_version.minor=2

     ###############################################################
     # IIOP 1.2 specific parameters

     # Set to True to enable IIOP 1.2
     #polyorb.protocols.iiop.giop.1.2.enable=true

     # Set to True to send a locate message prior to the request
     #polyorb.protocols.iiop.giop.1.2.locate_then_request=true

     # Maximum message size before fragmenting request
     #polyorb.protocols.iiop.giop.1.2.max_message_size=1000

     ###############################################################
     # IIOP 1.1 specific parameters

     # Set to True to enable IIOP 1.1
     #polyorb.protocols.iiop.giop.1.1.enable=true

     # Set to True to send a locate message prior to the request
     #polyorb.protocols.iiop.giop.1.1.locate_then_request=true

     # Maximum message size before fragmenting request
     #polyorb.protocols.iiop.giop.1.1.max_message_size=1000

     ###############################################################
     # IIOP 1.0 specific parameters

     # Set to True to enable IIOP 1.0
     #polyorb.protocols.iiop.giop.1.0.enable=true

     # Set to True to send a locate message prior to the request
     #polyorb.protocols.iiop.giop.1.0.locate_then_request=true

11.3.3 SSLIOP Configuration Parameters
--------------------------------------

11.3.3.1 Ciphers name
.....................

PolyORB's SSLIOP uses the OpenSSL library to support all ciphers
recommended by CORBA 3.0.3. The OpenSSL library uses specific names for
ciphers. The table below contains CORBA-recommended cipher names and
their OpenSSL equivalents:

CORBA recommended ciphers                   OpenSSL equivalent
TLS_RSA_WITH_RC4_128_MD5                    RC4-MD5
SSL_RSA_WITH_RC4_128_MD5                    RC4-MD5
TLS_DHE_DSS_WITH_DES_CBC_SHA                EDH-DSS-CBC-SHA
SSL_DHE_DSS_WITH_DES_CBC_SHA                EDH-DSS-CBC-SHA
TLS_RSA_EXPORT_WITH_RC4_40_MD5              EXP-RC4-MD5
SSL_RSA_EXPORT_WITH_RC4_40_MD5              EXP-RC4-MD5
TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA       EXP-EDH-DSS-DES-CBC-SHA
SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA       EXP-EDH-DSS-DES-CBC-SHA

11.3.3.2 SSLIOP Parameters
..........................

     ###############################################################################
     # SSLIOP parameters
     #

     [ssliop]

     ###############################################################
     # SSLIOP Global Settings

     # SSLIOP's default port
     #polyorb.protocols.ssliop.default_port=2810
     # If no SSLIOP default address is provide, PolyORB reuses IIOP's
     # address

     # Private Key file name
     #polyorb.protocols.ssliop.privatekeyfile=privkey.pem

     # Certificate file name
     #polyorb.protocols.ssliop.certificatefile=cert.pem

     # Trusted CA certificates file
     #polyorb.protocols.ssliop.cafile=cacert.pem

     # Trusted CA certificates path
     #polyorb.protocols.ssliop.capath=demoCA/certs

     # Disable unprotected invocations
     #polyorb.protocols.ssliop.disable_unprotected_invocations=true

     ###############################################################
     # Peer certificate verification mode

     # Verify peer certificate
     #polyorb.protocols.ssliop.verify=false

     # Fail if client did not return certificate. (server side option)
     #polyorb.protocols.ssliop.verify_fail_if_no_peer_cert=false

     # Request client certificate only once. (server side option)
     #polyorb.protocols.ssliop.verify_client_once=false

11.3.4 DIOP Configuration Parameters
------------------------------------

     ###############################################################
     # DIOP Global Settings

     # Preference level for DIOP
     #polyorb.binding_data.diop.preference=0

     # DIOP's default address
     #polyorb.protocols.diop.default_addr=127.0.0.1

     # DIOP's default port
     #polyorb.protocols.diop.default_port=12345

     # Default GIOP/DIOP Version
     #polyorb.protocols.diop.giop.default_version.major=1
     #polyorb.protocols.diop.giop.default_version.minor=2

     ###############################################################
     # DIOP 1.2 specific parameters

     # Set to True to enable DIOP 1.2
     #polyorb.protocols.diop.giop.1.2.enable=true

     # Maximum message size
     #polyorb.protocols.diop.giop.1.2.max_message_size=1000

     ###############################################################
     # DIOP 1.1 specific parameters

     # Set to True to enable DIOP 1.1
     #polyorb.protocols.diop.giop.1.1.enable=true

     # Maximum message size
     #polyorb.protocols.diop.giop.1.1.max_message_size=1000

     ###############################################################
     # DIOP 1.0 specific parameters

     # Set to True to enable DIOP 1.0
     #polyorb.protocols.diop.giop.1.0.enable=true

11.3.5 MIOP Configuration Parameters
------------------------------------

     ###############################################################################
     # MIOP parameters
     #

     [miop]

     ###############################################################
     # MIOP Global Settings

     # Preference level for MIOP
     #polyorb.binding_data.uipmc.preference=0

     # Maximum message size
     #polyorb.miop.max_message_size=6000

     # Time To Leave parameter
     #polyorb.miop.ttl=15

     # Multicast address to use
     # These two parameters must be set explicitly, no default value is provided.
     # If either parameter is unset, the MIOP access point is disabled.
     #polyorb.miop.multicast_addr=<group-ip-address>
     #polyorb.miop.multicast_port=<port-number>

     # Set to True to enable MIOP
     #polyorb.protocols.miop.giop.1.2.enable=false

     # Maximum message size
     #polyorb.protocols.miop.giop.1.2.max_message_size=1000

11.4 Code sets
==============

This sections details the various steps required to add support for new
character code sets to PolyORB's GIOP personality. Please refer to the
CORBA specifications (`[OMG04]'), par. 13.10 for more details on this
topic.

11.4.1 Supported code sets
--------------------------

PolyORB supports the following list of code sets:

  1. Available char data code sets:
       1. 16#00010001#   ISO 8859-1:1987; Latin Alphabet No. 1

       2. 16#05010001#   X/Open UTF-8; UCS Transformation Format 8
          (UTF-8)

  2. Available wchar data code sets:
       1. 16#00010100#   ISO/IEC 10646-1:1993; UCS-2, Level 1

       2. 16#00010109#   ISO/IEC 10646-1:1993; UTF-16, UCS
          Transformation Format 16-bit form

11.4.2 Incompatibility in code set support
------------------------------------------

Some ORBs report incompatiblity in code sets because fallback
converters are not explicitly present in the reference.  To work around
this issue, you may use the following parameters:

     [giop]
     giop.add_char_fallback_code_set=true
     giop.add_wchar_fallback_code_set=true

11.4.3 Adding support for new code sets
---------------------------------------

PolyORB allows users to extend the set of supported native character
code sets. Adding support for new character code set consists of the
following steps:

  1. Developing sets of Converters - special objects that do
     marshalling/unmarshalling operations of character data. At least
     two Converters are required: for direct marshalling character data
     in native code set and for marshalling/unmarshalling character
     data in fallback character code set (UTF-8 for char data and
     UTF-16 for wchar data). Additional Converters may be developed for
     marshalling character data in conversion code set.

  2. Developing converter factory subprogram for each Converter.

  3. Registering native code set, its native and fallback converters
     and optional conversion char sets and its converters.

11.4.4 Character data Converter
-------------------------------

Character data converters do direct marshalling/unmarshalling of
character data (char or wchar - depending on `Converter') into/from
PolyORB's buffer. This allows to minimize the speed penalty on
character data marshalling.

   Character data Converters for char data have the following API (from
`PolyORB.GIOP_P.Code_Sets.Converters' package:

        type Converter is abstract tagged private;

        procedure Marshall
          (C      : Converter;
           Buffer : access Buffers.Buffer_Type;
           Data   : Types.Char;
           Error  : in out Errors.Error_Container)
           is abstract;

        procedure Marshall
          (C      : Converter;
           Buffer : access Buffers.Buffer_Type;
           Data   : Types.String;
           Error  : in out Errors.Error_Container)
           is abstract;

        procedure Unmarshall
          (C      : Converter;
           Buffer : access Buffers.Buffer_Type;
           Data   :    out Types.Char;
           Error  : in out Errors.Error_Container)
           is abstract;

        procedure Unmarshall
          (C      : Converter;
           Buffer : access Buffers.Buffer_Type;
           Data   :    out Types.String;
           Error  : in out Errors.Error_Container)
           is abstract;

   The Marshall subprograms do marshalling of one character or string of
characters into the buffer. The Unmarshall subprograms do unmarshalling
of one character or string of characters from the buffer.

   Note: Depending on the item size of the data (char/wchar) and GIOP
version, marshalling/unmarshalling algorithms may vary. In some
situations marshalling of string is not equivalent to marshalling its
length and marshalling one by one each character. Please refere to GIOP
specifications for more details.

   If marshalling/unmarshalling fails, subprograms must set the Error
parameter to the corresponding error, usually `Data_Conversion_E'.

   Note: We recommend to always use the Data_Conversion_E error code
with Minor status 1.

   All `Converters' (native, fallback and conversion) have similar
APIs.  Wchar data converters differ only in parameter type.

11.4.5 Converters factories
---------------------------

To create new converters, PolyORB uses special factory subprograms with
the following profile:

        function Factory return Converter_Access;

   or

        function Factory return Wide_Converter_Access;

   This function must allocate a new `Converter' and initialize its
state.

11.4.6 Registering new code sets
--------------------------------

Registering new native character data code sets begins from registering
new native character data code sets and its native and fallback
`Converters'. This is done using `Register_Native_Code_Set':

        procedure Register_Native_Code_Set
          (Code_Set : Code_Set_Id;
           Native   : Converter_Factory;
           Fallback : Converter_Factory);

   or

        procedure Register_Native_Code_Set
          (Code_Set : Code_Set_Id;
           Native   : Wide_Converter_Factory;
           Fallback : Wide_Converter_Factory);

   If you have additional conversion code sets Converters you may
register it by calling Register_Conversion_Code_Set subprogram:

        procedure Register_Conversion_Code_Set
          (Native     : Code_Set_Id;
           Conversion : Code_Set_Id;
           Factory    : Converter_Factory);

   or

        procedure Register_Conversion_Code_Set
          (Native     : Code_Set_Id;
           Conversion : Code_Set_Id;
           Factory    : Wide_Converter_Factory);

   Note: because of incompatibility in the support of code sets
negotiation in some ORB's it is recommend to recognize two boolean
PolyORB's parameters:

     [giop]
     giop.add_char_fallback_code_set=false
     giop.add_wchar_fallback_code_set=false

   and also register a fallback Converter as conversion Converter if the
corresponding parameter is set to True.

   Finally, define your preferred native character data code sets by
parameters (only integer code sets codes now supported):

     [giop]
     giop.native_char_code_set=16#00010001#
     giop.native_wchar_code_set=16#00010100#

12 SOAP
*******

12.1 Installing SOAP protocol personality
=========================================

Ensure PolyORB has been configured and then compiled with the SOAP
protocol personality. See *note Building an application with PolyORB::
for more details on how to check installed personalities.

   To enable configuration of the SOAP application personality, *note
Installation::.

12.2 Configuring the SOAP personality
=====================================

The SOAP personality is configured using a configuration file. See
*note Using a configuration file:: for more details.

   Here is a summary of available parameters for each instance of SOAP.

     ###############################################################################
     # SOAP parameters
     #

     [soap]

     ###############################################################
     # SOAP Global Settings

     # Preference level for SOAP
     #polyorb.binding_data.soap.preference=0

     # SOAP's default address
     #polyorb.protocols.soap.default_addr=127.0.0.1

     # SOAP's default port
     #polyorb.protocols.soap.default_port=8080

13 Tools
********

13.1 `po_catref'
================

`po_catref' is a utility for viewing the components of a stringified
reference (CORBA IOR, corbaloc or URI). The reference's components
include references to access an object through multiple protocols (e.g.
CORBA IIOP, SOAP) and configuration parameters associated with a
reference (e.g. GIOP Service Contexts).

     Usage:
            po_catref <stringified reference>

Note: `po_catref' can only process protocols PolyORB has been
configured with.

13.2 `po_dumpir'
================

`po_dumpir' is a utility for viewing the content of an instance of the
CORBA Interface Repository.

     Usage:
            po_dumpir <stringified reference>

Note: `po_dumpir' will be compiled and installed only if the CORBA
personality and the `ir' service is compiled. Please see *note Building
an application with PolyORB:: for more details on how to set up PolyORB.

13.3 `po_names'
===============

`po_names' is a stand-alone name server. It has an interface similar to
CORBA COS Naming, without dragging in any dependencies on CORBA
mechanisms. This name server is to be used when the CORBA application
personality is not required, e.g. with the DSA or MOMA application
personalities.

Appendix A Performance considerations
*************************************

This section discusses performance when using PolyORB. Many elements
can be configured, *Note Building an application with PolyORB::.  By
carefully selecting them, you can increase the throughput of your
application.

   We review some parameters that can impact performance.

   * Build options:
        * For production use, you should not build PolyORB with debug
          activated.

   * Tasking policies:
        * You should carefully select the tasking policy to reduce
          dynamic ressource allocation (tasks, entry points, etc.).
          *Note Tasking model in PolyORB::.

   * Transport parameters:
        * Setting `tcp.nodelay' to false will disable Nagle buffering.

   * GIOP parameters:
        * Setting
          `polyorb.protocols.iiop.giop.1.X.locate_then_request', where
          `X' is the GIOP version in use, to false will disable
          `Locate_Message', reducing the number of requests exchanged,

        * Increasing
          `polyorb.protocols.iiop.giop.1.X.max_message_size', where `X'
          is the GIOP version in use, will reduce GIOP fragmentation,
          reducing middleware processing.

Appendix B Conformance to standards
***********************************

B.1 CORBA standards conformance
===============================

The OMG defines a CORBA-compliant ORB as an implementation of the CORBA
specifications that supports CORBA Core and one mapping of CORBA's IDL.

   Here is a summary of PolyORB's conformance issues with the latest
CORBA specifications (revision 3.0, formal/02-06-01).

B.1.1 CORBA IDL-to-Ada mapping
------------------------------

PolyORB supports the IDL-to-Ada specification `[OMG01]', with the
following limitations in both the CORBA API and the IDL-to-Ada compiler
`idlac':

   * no support for abstract interfaces, object-by-value, context data;

   * no support for CORBA Components;

   * implemented API may present some divergences with current mapping.

   Note: generated code is constrained by the limitations of the Ada
compiler used. Please refer to its documentation for more information.

   Conforming to documentation requirements from section 4.11 of the
IDL-to-Ada specification `[OMG01]', note that PolyORB's implementation
of CORBA is tasking-safe. The use of the CORBA personality on typical
GNAT runtimes is task-blocking, unless specified in platform notes.

B.1.2 CORBA Core
----------------

This set encompasses chapters 1-11. Chapters 3 to 11 are normative.

   * Chapter 3 describes OMG IDL syntax and semantics. See *note CORBA
     IDL-to-Ada mapping:: for a description of non-implemented features;

   * Chapter 4 describes the ORB Interface.

     PolyORB partially supports this chapter.

   * Chapter 5 describes Value Type Semantics.

     PolyORB does not support this chapter.

   * Chapter 6 describes Abstract Interface Semantics.

     PolyORB does not support this chapter.

   * Chapter 7 describes Dynamic Invocation Interface (DII)

     PolyORB supports only the following methods: `Create_Request',
     `Invoke' and `Delete'.

   * Chapter 8 describes Dynamic Skeleton Interface (DSI)

     PolyORB partially supports this chapter: this interface is fully
     implemented except for context data.

   * Chapter 9 describes Dynamic Management of Any Values

     PolyORB partially supports this chapter: this interface is fully
     implemented except for object references and value types.

   * Chapter 10 describes The Interface Repository

     PolyORB supports this chapter, except for the `ExtValueDef'
     interface, and all CORBA CCM related interfaces.

   * Chapter 11 describes The Portable Object Adapter

     PolyORB supports this chapter with the following limitations:
        * the `USE_SERVANT_MANAGER' policy is partially supported: the
          `ServantLocator' object is not implemented;

        * support for `SINGLE_THREAD' policy is incomplete, reentrant
          calls may not work;

        * `Wait_For_Completion' and `Etherealize_Objects' are not taken
          into account in `PortableServer.POAManager';

        * the `PortableServer.POAManagerFactory' API is not implemented.


B.1.3 CORBA Interoperability
----------------------------

This set encompasses chapters 12-16.

   * See *note CORBA-GIOP standards conformance:: for more information
     on this point.


B.1.4 CORBA Interworking
------------------------

This set encompasses chapters 17-21.

   * Chapters 17 to 20 describe interoperability with Microsoft's
     COM/DCOM.

     PolyORB provides no support for these chapters.

   * Chapter 21 describes `PortableInterceptor'.

     PolyORB provides partial support for this chapter.


B.1.5 CORBA Quality Of Service
------------------------------

This set encompasses chapters 22-24.

   * Chapter 22 describes CORBA Messaging

   * Chapter 23 describes Fault Tolerant CORBA

   * Chapter 24 describes Secure Interoperability.


PolyORB provides no support for these chapters.

B.1.6 CORBA COS Services
------------------------

COS Services are specifications of high level services that are
optional extensions to the CORBA specification. They provide helper
packages to build distributed applications.  PolyORB implements the
following COS Services:

   * COS Event and TypedEvent;

   * COS Naming;

   * COS Notification;

   * COS Time;

B.1.7 CORBA Specialized services
--------------------------------

PolyORB supports the following specialized services:

   * Unreliable Multicast (MIOP), proposed 1.0 specification `[OMG02b]'.  

   * RT-CORBA extensions, see *note RT-CORBA:: for more information on
     this point.

   * CORBA security extensions, see `[OMG]' for more information on
     this point.


B.2 RT-CORBA standards conformance
==================================

RT-CORBA specifications rely on the CORBA application personality; the
same issues and implementation notes apply.

   In addition, here is a list of issues with the implementation of
RT-CORBA static `[OMG02a]' and dynamic scheduling `[OMG03]'
specifications.

   * RT-CORBA static and dynamic scheduling (Chapter 2)

     Chapter 2 is common to these two specifications. It describes key
     mechanisms of RT-CORBA that are common to both specifications.

     PolyORB partially implements this chapter from section 2.1 up to
     section 2.10. PolyORB does not provide support for all
     connection-related policies.

     See implementation notes in the different package specifications
     for more details.

   * RT-CORBA static scheduling (Chapter 3)

     PolyORB supports this chapter.

   * RT-CORBA dynamic scheduling (Chapter 3)

     PolyORB does not support this chapter.


B.3 CSIv2 standards conformance
===============================

PolyORB supports IIOP/SSL.

B.4 CORBA/GIOP standards conformance
====================================

GIOP supports part of the CORBA Interoperability specification, from
chapters 12 to 16 of CORBA specifications.

   Chapter 12 defines general concepts about ORB interoperability. It
defines an _interoperbility-compliant ORB_ as an ORB that supports:

   * API that supports the construction of request-level inter-ORB
     bridges, Dynamic Invocation Interface, Dynamic Skeleton Interface
     and the object identity operations described in the Interface
     Repository. See *note CORBA standards conformance:: for more
     details.

   * IIOP protocol as defined in chapter 15.

Support for other components is optional.

   * Chapter 13 describes the ORB Interoperability Architecture.

     PolyORB fully supports this chapter.

   * Chapter 14 describes how to build Inter-ORB Bridges.

     PolyORB fully supports this chapter.

   * Chapter 15 describes the General Inter-ORB Protocol (GIOP).

     PolyORB supports GIOP version 1.0 to 1.2, the CDR representation
     scheme.  Support for IOR and `corbaloc' addressing mechanisms is
     supported in the CORBA personality, see *note CORBA:: for more
     details.

     PolyORB does not support the optional IIOP IOR Profile Components,
     Bi-directional GIOP. PolyORB also does not support fragmentation
     in GIOP 1.1.

   * Chapter 16 describes the DCE ESIOP protocol.

     PolyORB does not support this optional chapter.


B.5 SOAP standards conformance
==============================

The documentation of the SOAP standards conformance of PolyORB will
appear in a future revision of PolyORB.

Appendix C References
*********************

  1. [DB98] B. Dobbing and A. Burns.  The Ravenscar tasking profile for
     high integrity real-time programs.  In `Proceedings of SigAda'98',
     Washington, DC, USA, November 1998.

  2. [gla06] `GLADE User's Guide r 1.54', February 2006.

  3. [ISO95] ISO.  `Information Technology - Programming Languages -
     Ada'.  ISO, February 1995.  ISO/IEC/ANSI 8652:1995.

  4. [ISO06] ISO.  `Information Technology - Programming Languages -
     Ada'.  ISO, November 2006.  ISO/IEC 8652:1995 with Technical
     Corrigendum 1 and Amendment 1 ("Ada 2005").

  5. [Obr03] P. Obry.  Ada Web Server (AWS) 1.3, 2003.

  6. [OMG] OMG.  `Common Secure Interoperability (CSIv2)'.  OMG.

  7. [OMG01] OMG.  `Ada Language Mapping Specification, v1.2'.  OMG,
     October 2001.  OMG Technical Document formal/2001-10-42.

  8. [OMG02a] OMG.  `Real-Time CORBA Specification, static scheduling,
     v1.1'.  OMG, April 2002.  OMG Technical Document formal/2002-08-02.

  9. [OMG02b] OMG.  `unreliable Multicast InterORB Protocol
     specification'.  OMG, 2002.  OMG Technical Document ptc/03-01-11.

 10. [OMG03] OMG.  `Real-Time CORBA Specification, dynamic scheduling,
     v2.0'.  OMG, April 2003.  OMG Technical Document formal/2003-11-01.

 11. [OMG04] OMG.  `The Common Object Request Broker: Architecture and
     Specification,   revision 3.0.3'.  OMG, March 2004.  OMG Technical
     Document formal/2004-03-12.

 12. [SUN99] SUN.  Java Message Service, 1999.

 13. [W3C00] W3C.  `Extensible Markup Language (XML) 1.0', October 2000.
     W3C recommandation.

 14. [W3C03] W3C.  `Simple Object Access Protocol (SOAP) 1.2: primer',
     june 2003.  W3C recommandation.


Appendix D GNU Free Documentation License
*****************************************

Version 1.1, March 2000

Copyright (C) 2000 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

0. PREAMBLE
===========

The purpose of this License is to make a manual, textbook, or other
written document "free" in the sense of freedom: to assure everyone the
effective freedom to copy and redistribute it, with or without
modifying it, either commercially or noncommercially.  Secondarily,
this License preserves for the author and publisher a way to get credit
for their work, while not being considered responsible for
modifications made by others.

   This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft license
designed for free software.

   We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals; it
can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS
================================

This License applies to any manual or other work that contains a notice
placed by the copyright holder saying it can be distributed under the
terms of this License.  The "Document", below, refers to any such
manual or work.  Any member of the public is a licensee, and is
addressed as "you".

   A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.

   A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall subject
(or to related matters) and contains nothing that could fall directly
within that overall subject.  (For example, if the Document is in part a
textbook of mathematics, a Secondary Section may not explain any
mathematics.)  The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding them.

   The "Invariant Sections" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.

   The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.

   A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the general
public, whose contents can be viewed and edited directly and
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input to
text formatters.  A copy made in an otherwise Transparent file format
whose markup has been designed to thwart or discourage subsequent
modification by readers is not Transparent.  A copy that is not
"Transparent" is called "Opaque".

   Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format, SGML or
XML using a publicly available DTD, and standard-conforming simple HTML
designed for human modification.  Opaque formats include PostScript,
PDF, proprietary formats that can be read and edited only by
proprietary word processors, SGML or XML for which the DTD and/or
processing tools are not generally available, and the machine-generated
HTML produced by some word processors for output purposes only.

   The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page.  For works in
formats which do not have any title page as such, "Title Page" means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.

2. VERBATIM COPYING
===================

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.

   You may also lend copies, under the same conditions stated above, and
you may publicly display copies.

3. COPYING IN QUANTITY
======================

If you publish printed copies of the Document numbering more than 100,
and the Document's license notice requires Cover Texts, you must enclose
the copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify you
as the publisher of these copies.  The front cover must present the
full title with all words of the title equally prominent and visible.
You may add other material on the covers in addition.  Copying with
changes limited to the covers, as long as they preserve the title of
the Document and satisfy these conditions, can be treated as verbatim
copying in other respects.

   If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

   If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a publicly-accessible computer-network location containing a complete
Transparent copy of the Document, free of added material, which the
general network-using public has access to download anonymously at no
charge using public-standard network protocols.  If you use the latter
option, you must take reasonably prudent steps, when you begin
distribution of Opaque copies in quantity, to ensure that this
Transparent copy will remain thus accessible at the stated location
until at least one year after the last time you distribute an Opaque
copy (directly or through your agents or retailers) of that edition to
the public.

   It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of copies, to
give them a chance to provide you with an updated version of the
Document.

4. MODIFICATIONS
================

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release the
Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy of
it.  In addition, you must do these things in the Modified Version:
  A. Use in the Title Page (and on the covers, if any) a title distinct
       from that of the Document, and from those of previous versions
     (which should, if there were any, be listed in the History section
       of the Document).  You may use the same title as a previous
     version    if the original publisher of that version gives
     permission.

  B. List on the Title Page, as authors, one or more persons or entities
       responsible for authorship of the modifications in the Modified
      Version, together with at least five of the principal authors of
     the    Document (all of its principal authors, if it has less than
     five).

  C. State on the Title page the name of the publisher of the
     Modified Version, as the publisher.

  D. Preserve all the copyright notices of the Document.

  E. Add an appropriate copyright notice for your modifications
     adjacent to the other copyright notices.

  F. Include, immediately after the copyright notices, a license notice
       giving the public permission to use the Modified Version under
     the    terms of this License, in the form shown in the Addendum
     below.

  G. Preserve in that license notice the full lists of Invariant
     Sections    and required Cover Texts given in the Document's
     license notice.

  H. Include an unaltered copy of this License.

  I. Preserve the section entitled "History", and its title, and add to
       it an item stating at least the title, year, new authors, and
     publisher of the Modified Version as given on the Title Page.  If
      there is no section entitled "History" in the Document, create one
       stating the title, year, authors, and publisher of the Document
     as    given on its Title Page, then add an item describing the
     Modified    Version as stated in the previous sentence.

  J. Preserve the network location, if any, given in the Document for
     public access to a Transparent copy of the Document, and likewise
      the network locations given in the Document for previous versions
       it was based on.  These may be placed in the "History" section.
       You may omit a network location for a work that was published at
       least four years before the Document itself, or if the original
      publisher of the version it refers to gives permission.

  K. In any section entitled "Acknowledgements" or "Dedications",
     preserve the section's title, and preserve in the section all the
      substance and tone of each of the contributor acknowledgements
     and/or dedications given therein.

  L. Preserve all the Invariant Sections of the Document,    unaltered
     in their text and in their titles.  Section numbers    or the
     equivalent are not considered part of the section titles.

  M. Delete any section entitled "Endorsements".  Such a section    may
     not be included in the Modified Version.

  N. Do not retitle any existing section as "Endorsements"    or to
     conflict in title with any Invariant Section.

   If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.

   You may add a section entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various parties -
for example, statements of peer review or that the text has been
approved by an organization as the authoritative definition of a
standard.

   You may add a passage of up to five words as a Front-Cover Text, and
a passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or through
arrangements made by) any one entity.  If the Document already includes
a cover text for the same cover, previously added by you or by
arrangement made by the same entity you are acting on behalf of, you
may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

   The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS
======================

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice.

   The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of Invariant
Sections in the license notice of the combined work.

   In the combination, you must combine any sections entitled "History"
in the various original documents, forming one section entitled
"History"; likewise combine any sections entitled "Acknowledgements",
and any sections entitled "Dedications".  You must delete all sections
entitled "Endorsements."

   Heading 6. COLLECTIONS OF DOCUMENTS

   You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy that
is included in the collection, provided that you follow the rules of
this License for verbatim copying of each of the documents in all other
respects.

   You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert a
copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.

7. AGGREGATION WITH INDEPENDENT WORKS
=====================================

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, does not as a whole count as a Modified Version of
the Document, provided no compilation copyright is claimed for the
compilation.  Such a compilation is called an "aggregate", and this
License does not apply to the other self-contained works thus compiled
with the Document, on account of their being thus compiled, if they are
not themselves derivative works of the Document.

   If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one quarter
of the entire aggregate, the Document's Cover Texts may be placed on
covers that surround only the Document within the aggregate.  Otherwise
they must appear on covers around the whole aggregate.

8. TRANSLATION
==============

Translation is considered a kind of modification, so you may distribute
translations of the Document under the terms of section 4.  Replacing
Invariant Sections with translations requires special permission from
their copyright holders, but you may include translations of some or
all Invariant Sections in addition to the original versions of these
Invariant Sections.  You may include a translation of this License
provided that you also include the original English version of this
License.  In case of a disagreement between the translation and the
original English version of this License, the original English version
will prevail.

9. TERMINATION
==============

You may not copy, modify, sublicense, or distribute the Document except
as expressly provided for under this License.  Any other attempt to
copy, modify, sublicense or distribute the Document is void, and will
automatically terminate your rights under this License.  However,
parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such parties
remain in full compliance.

10. FUTURE REVISIONS OF THIS LICENSE
====================================

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time.  Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns.  See
http://www.gnu.org/copyleft/.

   Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.

ADDENDUM: How to use this License for your documents
====================================================

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

     Copyright (c)  YEAR  YOUR NAME.
     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.1 or any later version published by the Free Software
     Foundation; with the Invariant Sections being LIST THEIR TITLES,
     with the Front-Cover Texts being LIST, and with the Back-Cover
     Texts being LIST.  A copy of the license is included in the
     section entitled "GNU Free Documentation License".

   If you have no Invariant Sections, write "with no Invariant Sections"
instead of saying which ones are invariant.  If you have no Front-Cover
Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being
LIST"; likewise for Back-Cover Texts.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.

Index
*****

Application personalities:                     See 3.1.      (line  850)
AWS, Ada Web Server <1>:                       See 10.       (line 5799)
AWS, Ada Web Server:                           See 3.1.4.    (line  889)
Code sets, GIOP:                               See 11.4.     (line 6108)
Configuration, CORBA:                          See 6.7.      (line 2333)
Configuration, GIOP:                           See 11.3.     (line 5862)
Configuration, PolyORB:                        See 4.        (line  935)
Conventions:
          See ``Conventions''.                               (line  334)
CORBA <1>:                                     See 6.        (line 1580)
CORBA:                                         See 3.1.1.    (line  859)
CORBA COS Naming:                              See 6.4.1.    (line 1829)
CORBA IDL-to-Ada mapping:                      See B.1.1.    (line 6415)
CORBA, COS Services <1>:                       See B.1.6.    (line 6529)
CORBA, COS Services:                           See 3.1.1.    (line  859)
CORBA, Server-side exception:                  See 6.8.7.    (line 2631)
CORBA, Specialized services:                   See B.1.7.    (line 6545)
CORBA::Unknown:                                See 6.8.7.    (line 2631)
Debugging traces:                              See 4.4.      (line 1185)
DIOP <1>:                                      See 11.2.3.   (line 5845)
DIOP:                                          See 3.2.1.    (line  920)
DSA, Distributed Systems Annex <1>:            See 8.        (line 3152)
DSA, Distributed Systems Annex:                See 3.1.2.    (line  874)
Exceptions:                                    See 4.5.      (line 1212)
Free Documentation License, GNU:               See Appendix D.
                                                             (line 6689)
GIOP <1>:                                      See 11.3.1.   (line 5870)
GIOP <2>:                                      See 11.       (line 5805)
GIOP:                                          See 3.2.1.    (line  905)
GNU Free Documentation License:                See Appendix D.
                                                             (line 6689)
iac:                                           See 6.3.1.    (line 1608)
idlac:                                         See 6.3.2.    (line 1725)
IIOP <1>:                                      See 11.2.1.   (line 5824)
IIOP:                                          See 3.2.1.    (line  911)
License, GNU Free Documentation:               See Appendix D.
                                                             (line 6689)
MIOP <1>:                                      See B.1.7.    (line 6547)
MIOP <2>:                                      See 11.2.4.   (line 5855)
MIOP:                                          See 3.2.1.    (line  917)
MOMA, Message Oriented Middleware for Ada <1>: See 9.        (line 5766)
MOMA, Message Oriented Middleware for Ada:     See 3.1.3.    (line  882)
Personalities:                                 See 3.        (line  838)
po_catref:                                     See 13.1.     (line 6333)
po_cos_naming:                                 See 6.4.1.    (line 1829)
po_dumpir:                                     See 13.2.     (line 6348)
po_ir:                                         See 6.5.1.    (line 1883)
po_names:                                      See 13.3.     (line 6361)
PolyORB:                                       See 1.        (line  368)
polyorb-config:                                See 4.7.      (line 1242)
polyorb.conf:                                  See 4.2.1.    (line 1041)
PolyORB.CORBA_P.CORBALOC:                      See 6.9.1.    (line 2687)
PolyORB.CORBA_P.Naming_Tools:                  See 6.9.2.    (line 2736)
PolyORB.CORBA_P.Server_Tools:                  See 6.9.3.    (line 2836)
polyorb.gpr:                                   See 4.6.      (line 1218)
PolyORB.RTCORBA_P.Setup:                       See 7.3.1.    (line 2950)
POLYORB_CONF:                                  See 4.2.1.    (line 1041)
Protocol personality:                          See 3.2.      (line  898)
Protocol personality, activation:              See 4.3.1.    (line 1135)
Ravenscar <1>:                                 See 5.1.3.    (line 1341)
Ravenscar:                                     See 4.1.1.    (line  957)
RT-CORBA <1>:                                  See 7.        (line 2927)
RT-CORBA:                                      See 3.1.1.    (line  859)
RTCORBA.PriorityMapping:                       See 7.4.      (line 3041)
RTCosScheduling Service:                       See 7.5.      (line 3056)
SOAP <1>:                                      See 12.       (line 6291)
SOAP:                                          See 3.2.2.    (line  926)
SSLIOP <1>:                                    See 11.2.2.   (line 5831)
SSLIOP:                                        See 3.2.1.    (line  914)
Tasking model:                                 See 5.        (line 1308)
Tasking runtime:                               See 5.1.      (line 1311)
Typographical conventions:
          See ``Conventions''.                               (line  334)
