Styles of messaging supported by XMS

XMS supports the point-to-point and publish/subscribe styles of messaging.

Styles of messaging are also called messaging domains.

Point-to-point messaging

If the underlying messaging and queuing system contains IBM Integration Bus, IBM Integration Bus might replicate a message and route copies of the message to different queues. As a result, more than one application can receive the message. IBM Integration Bus might also transform a message and add data to it.

A key characteristic of point-to-point messaging is that an application places a message onto a local queue when it sends a message. The underlying messaging and queuing system determines which destination queue the message is sent to. The receiving application retrieves the message from the destination queue.

Publish/subscribe messaging

A publisher supplies information in the form of publication messages. When a publisher publishes a message, it specifies a topic, which identifies the subject of the information inside the message.

A subscriber is a consumer of the information that is published. A subscriber specifies the topics it is interested in by creating subscriptions.

The publish/subscribe system receives publications from publishers and subscriptions from subscribers. It routes publications to subscribers. A subscriber receives publications on only those topics to which it subscribed.

A key characteristic of publish/subscribe messaging is that a publisher identifies a topic when it publishes a message. It does not identify the subscribers. If a message is published on a topic for which there are no subscribers, no application receives the message.

An application can be both a publisher and a subscriber.