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4.8: Web services - an overview

4.8: Web services - an overview

Web services are self-contained, modular applications that can be described, published, located, and invoked over a network. Web services could be weather reports or stock quotes. Transaction Web services, supporting business-to-business (B2B) or business-to-client (B2C) operations, could be airline reservations or purchase orders.

Web services reflect a new "service-oriented" approach to programming, based on the idea of building applications by discovering and implementing network-available services, or by invoking available applications to accomplish some task. This "service-oriented" approach is independent of specific programming languages or operating systems. Instead, Web services rely on pre-existing transport technologies (such as HTTP) and standard data encoding techniques (such as XML) for their implementation.

The Web services architecture describes three roles:

  1. Service provider
  2. Service requester
  3. Service broker
Web services components provide three basic operations:
  1. Publish
  2. Find
  3. Bind

In order for some component to become a Web service, it must be:

  • Created, and its interfaces and invocation methods must be defined
  • Published to some repository
  • Easy to locate by potential users
  • Invoked and implemented by users
  • Unpublished when it is no longer available
As illustrated in the graphic,
  • Web service descriptions can be created and published by service providers who create on-line resources for personal and business use.
  • Web services can be categorized and searched by specific broker services.
  • Web services can be located and invoked by requesters of the services.

Basic operations of Web services

With Web services, programming complexity is reduced because application designers do not have to worry about implementing the services they are invoking. Interactions in Web services are bound dynamically at runtime. A service requester describes the features of the required service and uses the service broker to find an appropriate service.

WebSphere Application Server supports making the following artifacts into Web services:

  • Java beans
  • Enterprise Java Beans
  • BSF supported scripts
  • DB2 stored procedures

See article Web services components for a description of the key components that comprise a Web service.

Visit URL, www.alphaworks.ibm.com/tech/webservicestoolkit, to access the Web services toolkit on Alphaworks. This site provides tools for creating WSDL files and SOAP clients, and describes working examples.

Learn more about Web services. Register for the Web services tutorial on Alphaworks.

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