Metatopics

WebSphere MQ Publish/Subscribe brokers provide information about publishers and subscribers via a special set of topics called metatopics. Metatopics start with the "MQ/S/" or "MQ/SA/" prefix, and are subscribed to by two categories of applications, administration programs and clients.

WebSphere Message Broker does not provide equivalent metatopics, and therefore a program (administration or client) that subscribes to WebSphere MQ Publish/Subscribe metatopics cannot work with a WebSphere Message Broker broker. However, WebSphere Message Broker does publish information about subscription events using its own set of system topics.

The following considerations apply to the two categories of application in the WebSphere Message Broker environment.

Administration programs (for example, the amqspsd sample) use WebSphere MQ Publish/Subscribe metatopics to display subscription information. This information is provided by WebSphere Message Broker in the workbench, which allows subscriptions to be viewed and deleted throughout the broker network.

Applications use messages published on WebSphere MQ Publish/Subscribe metatopics to, for example, request information about their own current subscriptions.

A client program can subscribe to WebSphere Message Broker system topics and process the event publications.

WebSphere Message Broker does not provide a topic that reports all the current subscriptions for a particular topic or client, but does publish whenever subscriptions are added or removed. This information is published as event information whereas WebSphere MQ Publish/Subscribe metatopics are published as state information.