The enterprise service bus as a concept has increasingly gained currency in the IT marketplace, even as vendor camps have squabbled over what exactly an ESB is. As a result, many organizations remain uncertain about the need for and role of an ESB in their IT infrastructures. Is an ESB just gussied-up message-oriented middleware, or is it a genuinely new approach to integration?

In response to client inquiries regarding the definition of an ESB, Mike Gilpin, an analyst at Forrester Research Inc., published a report in August that described the technology as "software infrastructure that enables service-oriented architectures (SOA) by acting as an intermediary layer of middleware through which a set of reusable business services are made widely available."

An ESB typically has some sort of "bus" messaging technology, such as Java Message Service or IBM's MQSeries, and support for Web services standards. The standards support is designed to let enterprises map data from disparate systems, route messages, ensure that services are delivered—and in the correct order—and enforce security rules automatically by using XML instead of changing code in the interfaces of services.