You connect the new system to the hub
and leverage the routing and transformation services. Figure 9-8 contrasts the custom
approach with the hub-and-spoke approach.
Oracle and Publish-Subscribe Technology
Oracle8i enhanced Advanced Queuing to include publish-subscribe functionality.
Applications can subscribe to a message queue by specifying the attributes of messages
they??™re interested in receiving. When another application publishes a message
by placing it in a queue, Oracle evaluates the contents of the message to determine
which of the subscribing applications are interested and notifies those applications.
For example, a shipping application can subscribe to a queue used for orders and
specify that only messages for orders with a status of ???Ready to Ship??? are of interest.
As messages representing these orders flow through the queue, the shipping application
will receive only the desired messages. This publish-subscribe functionality,
coupled with message propagation for routing, provides a very powerful messaging
backbone for information flow between systems.
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