What is an enterprise service bus?

Industry gadfly Don Box told a recent audience to get to work on new cool applications, and to spend less time writing XML standards. Well, he had a bit of a caveat there; he said if they were building an enterprise infrastructure bus, they should finish that first and then get to work on new cool apps.

What Box described sounded to us like the Enterprise Service Bus (ESB). Along with Service-Oriented Architectures (SOAs), WSDL and SOAP, it's been much discussed of late, but it might be useful to talk about what it is before running off to build one. The concept has the potential to change the way developers work, in the sense that it may lead to corporate interconnection standards for all in-house applications.

Its objective is IT's target from time immemorial: Islands of Automation.

Expert Sally Hudson, an IDC analyst, describes the Enterprise Service Bus as an open standards-based messaging means designed to provide interoperability between larger-grained applications and other components via simple standard adapters and interfaces. Hudson, like others, takes the term ''bus'' as it was once used in the old printed-circuit backboard communications bus days -- as a ready analogy for the envisioned service-oriented conduit of tomorrow. Ideally, she writes in an IDC paper, it is an asynchronous conduit. Today, such approaches are beginning to take form using Java Message Service (JMS) message-oriented middleware.

Certainly in the forefront of such bus talk is Sonic Software. The Sonic ESB supports service-based interactions based on XML and Web services standards, said Sonic Vice President Gordon Van Huizen, enabling developers to connect applications and services across the enterprise flexibly.

''We are focused on the middleware that connects services and meta applications. Some call them 'composite apps,''' he said.

Van Huizen further said that while the XML-based SOAP protocol has value, it is not yet ready for heavy duty; JMS and other means may be better for many inter-application communications for now.

''Lightweight asynchronous communication will eventually come, but it is taking longer than any of us imagined to get it standardized,'' he said.

One concept central to the Enterprise Service Bus is flexibility. As envisioned by Van Huizen and others, it supports multiple standards. He said Sonic added important elements that go to making such a bus when Progress Software, its parent firm, last year purchased XML specialist eXcelon.

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About the Author

Jack Vaughan is former Editor-at-Large at Application Development Trends magazine.


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