154 WebSphere Business Integration Message Broker Basics
5.3 Publish/subscribe
Publish/subscribe is a style of messaging in which messages that are produced
by a single application can be received and utilized by many other applications.
Publish/subscribe is a broad topic, and an in-depth discussion of its uses and
configuration is beyond the scope of this book. The Broker Administration
perspective in the Message Brokers Toolkit includes a number of tools to assist in
the configuration and administration of a publish/subscribe broker network, so a
brief description of the function of each tool is given here with a short overview of
publish/subscribe concepts.
As an additional source of information, and to try out some examples of
publish/subscribe using the Message Brokers Toolkit, try the Soccer and Scribble
samples that are provided in the samples gallery in the help system, as well as
the SurfWatch Getting Started sample. Note that the Getting Started samples
and Scribble sample are not supplied with WebSphere Business Integration
Event Broker as they contain nodes that are not available on that product, and
the Getting Started sample has a message set defined.
Publish/subscribe basics
An application known as a publisher generates a message that can be utilized by
other receiving applications known as
subscribers. The published message
contains publish/subscribe commands and information in the message header. A
published message is called a
publication. There are two basic types of
publish/subscribe commands contained in the header: one to register a
subscription and the other to publish a message. Both messages show a
message topic. A subscriber subscribes to messages of a particular topic using a
subscription message, and a publisher publishes a message about a given topic.
This is an example from the SurfWatch sample of a message for registering a
subscription:
<psc><Command>RegSub</Command><Topic>SouthShore</Topic><Topic>SunsetBeach</
Topic><Topic>Rockpile</Topic><Topic>Kahaluu</Topic><RegOpt>PersAsPub</RegOp
t><QName>PAGER</QName></psc>
This is an example from the SurfWatch sample of a publication:
<psc><Command>Publish</Command><Topic>Laniakea</Topic></psc><mcd><Msd>mrm</
Msd><Set>GettingStartedMessageSets</Set><Type>Pager</Type><Fmt>XML</Fmt></m
cd><Pager><Text>SurfWatch12.02.0420:57:18Laniakea: Onshore, waves
0m.</Text></Pager>
The various tools in the Broker Administration perspective can be used to set up
collections of brokers for use in publish/subscribe networks and to manage topics
and subscriptions as described in the following sections.

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