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See:
Description
Interface Summary | |
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EventCatalog | Remote interface for the event catalog enterprise bean in the Common Event Infrastructure. |
EventCatalogHome | Home interface for the event catalog enterprise bean in the Common Event Infrastructure. |
Class Summary | |
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EventDefinition | Represents an event definition. |
ExtendedDataElementDescription | Describes an extended data element that an event can contain. |
PropertyDescription | Describes a property that an event can contain. |
Exception Summary | |
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ArgumentNotValidException | Thrown when an event catalog method receives an argument that is not valid. |
CatalogException | Root exception for all exceptions that can be thrown by the event catalog component. |
DescriptionExistsException | Thrown when an attempt is made to add a description of an extended data element to an event definition and the event definition already contains a description for an extended data element of the same name, or likewise a property description and the event definition already contains a description for a property of the same name and path. |
EventDefinitionExistsException | Thrown when an attempt is made to add an event definition to the event
catalog and an event definition of the same name already exists but the
replace flag was set to false. |
EventDefinitionNotFoundException | Thrown when an attempt is made to refer to an event definition that does not exist in the event catalog. |
InheritanceNotValidException | Thrown when an attempt is made to add an event definition to the event catalog that violates the event definition inheritance rules. |
OperationNotValidException | Thrown when an event catalog method is called in a situation that is not valid. |
ParentNotValidException | Thrown when an attempt is made to add an event definition to the event catalog that does not name a valid parent. |
ValueTooLongException | Thrown when a value that is too long is passed to an event catalog method. |
XmlNotValidException | Thrown to indicate that an XML document containing event definitions is not valid. |
Exposes event metadata to Common Event Infrastructure client applications.
The event catalog is a repository of event metadata in the system. It allows other applications to understand the contents of an event based on its extension name. The rationale behind the event catalog component is that the Common Base Event model specifies the semantics for all event properties in the base event but not for individual extended data elements or context elements.
The main consumers of event catalog data are planning and configuration tools, which can be used to assist an operator to configure the system based on the expectation of a certain extended data element otherwise unknown to these applications. The Common Event Infrastructure hosts the event definitions, but the actual sources for event definition information are the external applications that flow their events through the Common Event Infrastructure. The Common Event Infrastructure does not provide sophisticated tools to assist an end user in creating event definitions because Common Event Infrastructure exploiters externally own these definitions.
For example, assume that an application produces events
of extension name Insurance_claim
containing an extended
data element called loss_type
that has fire
as one of its possible values. A configuration application for the event
bus routing policy can extract this information from the event catalog
and display it to someone planning the system deployment. Such information
can result in the system administrator configuring the event bus to send all
fire-related insurance claims to a topic called insurance/fire
.
As a second example, a graphical editor for correlation rules can use the event definition to allow the rule writer to browse the fields that are available within an event type and point only to the fields relevant to the rule execution. Going a step further, the event definition information can be used in this graphical rule editor to provide an auto-completion feature similar to the one available in WebSphere Studio Application Developer tool.
Another potential use of the event catalog is during runtime. For example, an application subscribed to the event bus can use the information in the event catalog to determine the integrity of an event notification. A correlation engine is a good example of an application that can follow this pattern.
Another use is the bi-directional mapping between categories of event sources and the Common Base Event extension names for the events that are produced by these sources. An application can consult the event catalog to determine all Common Base Event extension names (types of events) associated with a category of event sources, and vice-versa. From the event catalog perspective, the category of an event source is just a symbolic name, so that managing these categories is outside the scope of the Common Event Infrastructure architecture.
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