Implementing the Publish/Subscribe Pattern
The Observer pattern is pervasive in object-oriented computing and continues to make inroads with Web Services. In some schools of thought, the Publish/Subscribe pattern is synonymous with the Observer pattern, being essentially different terms for the same pattern. Other schools of thought treat the Publish/Subscribe pattern as slightly different in nature and more in line with some more robust event patterns, such as the Event Channel pattern that is a part of the Common Object Request Broker Architecture (CORBA). CORBA’s Event Channel pattern is a distributed computing pattern using proxies on both sides of a single event service. The service receives events from proxies and delivers events to proxies that register an interest for particular events. In this book, the Publish/Subscribe pattern is a subtle, but important, extension of the Observer pattern and a subset of the more robust Event Channel pattern. This book does not discuss the Event Channel pattern further. If you would like to learn more about the Event Channel pattern, you can locate the specification at the Object Management Group (OMG) Web site (http://www.omg.org).
KeywordsObject Management Group Uniform Resource Locator Common Object Request Broker Architecture Service Implementation Observer Pattern
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