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ESB Myth Busters: 10 Enterprise Service Bus Myths Debunked

Clarity of Definition for a Growing Phenomenon

Myth #2: Microsoft is building an ESB with their "Indigo" project.
Microsoft's Indigo combines Microsoft's Messaging Queuing, its Component Object Model COM+, .NET, and Web services. What they are building is a message bus with Web services extensions. This is very different from an enterprise bus. A messaging bus exposes the details of lower-level messaging techniques and requires the writing of code to define the relationships between applications and services. The mantra of the ESB is configuration rather than coding, which removes the necessity of hardwiring relationships between interconnected applications. An ESB facilitates and promotes the use of loose coupling between applications, which are exposed through the bus as event-driven services. The good news here is that applications built on Indigo will at least be message based and therefore easier to integrate through an ESB.

That said, there are elements of the BizTalk Server that, correctly combined with Indigo, could start to look like an ESB. However, there is one missing element in the formula, in that BizTalk is still a hub-and-spoke integration broker and is subject to all of the caveats mentioned in the ESB versus EAI discussion. You can't split out the XML transformation engine from the rest of the BizTalk Server and expect to run it as a load-balanced service across multiple machines without incurring the cost and overhead of the entire Biztalk Server (see the previous discussion on EAI vs. ESB).

Myth #3: The adoption of WS-* specifications, such as WS-Reliability and WS-Reliable Messaging, obviate the need for an ESB.
An ESB should be designed to accommodate these evolving specifications as they become mature and achieve commercial viability. Evolving WS-* specifications will help make application endpoints more interoperable through an ESB.

As part of the evolving standards process of Web services specifications, there exists much uncertainty due to the many overlapping efforts underway. As these specifications mature and achieve widespread adoption, they will still require an infrastructure to support them. An ESB can provide a consistent model for building, orchestrating, and managing SOAs, while insulating the IT organization from changes in underlying interoperability standards.

A WS-Reliability implementation requires that there be an industry-proven reliable message persistence and store-and-forward processor to support it. A foundational component of an ESB is an enterprise messaging layer that provides quality of service of message delivery through messaging conventions such as message persistence, store- and-forward delivery, message acknowledgements, and interfaces with external XA-compliant transaction managers. The ESB implementation may also provide transparent routing of messages across sophisticated network topologies, and continuous availability of the messaging infrastructure through a fault-tolerant messaging server architecture. The science of making all of this work together to ensure reliability under high-stress enterprise environments requires many person-years of effort to get right.

That being said, ESBs that are implemented today using a proprietary messaging layer should also adopt one or more of the WS-Rel* as additional protocols or "on-ramps" for getting on and off the bus. However, it is not a one-size-fits-all solution and many combinations of messaging and protocol support are necessary.

More Stories By Dave Chappell

David Chappell is vice president and chief technologist for SOA at Oracle Corporation, and is driving the vision for Oracle’s SOA on App Grid initiative.

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