WebSphere WebSphere Application Server Network Deployment, Version 6.0.x Operating Systems: AIX, HP-UX, Linux, Solaris, Windows

Topic spaces

A topic space is a hierarchy of topics used for publish/subscribe messaging. Topics with the same name can exist in multiple topic spaces, but there can be only one topic space with a given name in a service integration bus.

For example, consider a topic hierarchy split into the following topic spaces:
library
Topics for a document management.
sales
Topics for marketing and sales tracking.
The topic volumes can appear in the both topic spaces, and have very different meanings in each.

For publish/subscribe messaging, the administrator configures a topic space (a hierarchy of topics), but does not need to select any assigned member for the topicspace. A topic space has a publication point defined automatically on each messaging engine in the bus.

The topic space has a set of default publish and subscribe permissions for all topics in the hierarchy. An administrator can configure individual topics with specific permissions and mediations, and also inherit such configurations from higher topics in the topic space hierarchy, and from the topic space itself.

Every messaging engine in the service integration bus plays a logically-equivalent role in the distributed implementation of the topic space. A producing application can attach to any messaging engine in the bus, and messages are stored in the message store for the messaging engine to which the producer is attached. As a result, a topic space can have messages stored in a number of message stores at various (producing) messaging engines in the bus. Messages for a topic are published to a publication point and automatically forwarded to all other publication points for which there are subscribers on that topic.

A topic space and its publication points. Each publication, on a separate messaging engine, plays a logically-equivalent role in the distributed implementation of the topic space.

The default messaging provider supports the use of durable subscriptions to topics. This enables a subscriber to receive a copy of all messages published to a topic, even messages published during periods of time when the subscriber is not connected to the server.

For a given JMS connection factory, all messages to be delivered to durable subscriptions are stored on the publication point of the messaging engine named by the Durable subscription home property. If that messaging engine is unavailable, subscribers cannot retrieve messages until that messaging engine has restarted. Also, while that messaging engine is unavailable, any new messages to be delivered to durable subscriptions are preserved by the service integration bus until that messaging engine has restarted.

Related concepts
JMS topic resources and service integration
Related tasks
Creating a topic space for publish/subscribe messaging
Related reference
Topic names and use of wildcard characters in topic expressions

Concept topic

Terms of Use | Feedback

Last updated: 15 Mar 2007
http://publib.boulder.ibm.com/infocenter/wasinfo/v6r0/index.jsp?topic=/com.ibm.websphere.pmc.nd.doc\concepts\cjo0002_.html

© Copyright IBM Corporation 2004, 2007. All Rights Reserved.
This information center is powered by Eclipse technology. (http://www.eclipse.org)