Publish/Subscribe

In a publish/subscribe system, a publisher does not need to know who uses the information (publication) that it provides, and a subscriber does not need to know who provides the information that it receives as the result of a subscription.

Compare this with a point-to-point style of messaging application, in which the application that sends messages needs to know the destinations of the messages that it sends.

Queue managers make sure that messages arrive at the correct destinations, and are transformed to the format required at each destination.

A typical publish/subscribe system has more than one publisher and more than one subscriber, and often more than one queue manager. An application can be both a publisher and a subscriber.

The publisher generates a message that it wants to publish and defines the topic of the message.

A subscriber registers a request for a publication by specifying one of the following items:

• The topic, or topics, of the published messages that it is interested in.
• The subscription point from which it wants to receive publications.
• The content filter that should be applied to the published message.
• The name of the queue (known as the subscriber queue) on which publications that match the criteria selected are placed. This queue can be a cluster queue, so that publications can be distributed to clustered subscribers.