ESB (enterprise service bus) is an emerging standard for integrating enterprise applications in an implementation-independent fashion, at a coarse-grained service level via an event-driven and XML-based messaging engine.
The term is considered a catch-all by some. Recently, in an attempt to develop an open-source Web services framework, companies such as Iona Technologies, WSO2, Infravio Inc., Sonic Software Corp. and Blue Titan Software Inc. teamed up to bring together various projects to deliver what would amount to an open-source ESB.
However, sources said there was heated debate as to what to call it. While some wanted to call it an ESB, others did not. They settled on calling it a "Web services mediation framework."
According to a paper cited on a Weblog by Scott Woodgate, group product manager for BizTalk Server at Microsoft Corp., Microsofts integration strategy is to go beyond the ESB to meet user needs for messaging. The paper is entitled "Microsoft on the Enterprise Service Bus (ESB)."
"In short, if you are looking for ESB we can help you; but, on the other hand, we believe ESB is an incomplete implementation of integration, and we are price-point competitive to ESB with full integration server features," Woodgate said in his blog.
Indeed, "No single product or architecture satisfies all connected systems scenarios," the Microsoft paper said, adding, "The recent buzz around ESBs is rivaled only by the ambiguity by which the term is defined."
"The problem is that theres no sensible single definition of ESB," said Ronald Schmelzer, an analyst with ZapThink LLC, in Waltham, Mass. "The nominal one is that an ESB is some infrastructure for running distributed, reliable, event-driven services over an existing network. The problem is that not all ESB vendors define it the same way.
"Some include a messaging infrastructure, while others dont. Some include business process management, but others dont. Some others still define ESB as not even a product, but rather an architectural pattern, which begs the question that if ESB is an architectural pattern, then what is SOA [service-oriented architecture]?
"So, in the end analysis, the ESB term seems to be a transitional term to define the infrastructural approaches by which people implement SOA, but in the long term, it doesnt seem like the term will stick, as people become more specific about how they implement services in a loosely coupled way."
Microsofts strategy is to use BizTalk Server, WCF (Windows Communication Foundation, formerly known as "Indigo"), and the overall Windows platform to provide "message validation and transformation, business process orchestration and management, business activity monitoring and business rules management—all built on a foundation of industry-standard interoperable Web services," the paper said.
"I think they have something very similar to Artix in Indigo, so Id say they have something viable, although for Windows platforms only," Eric Newcomer, chief technology officer at Iona in Waltham, Mass., said of the Microsoft strategy.
"We are of course focused on fitting out legacy endpoints rather than Windows endpoints, and therefore we are oriented toward a development environment that assumes we are wrapping something else that already exists—i.e., service enabling an existing application. Microsoft, on the other hand, is assuming that you will be building most of your services from scratch in the Windows environment."
BizTalk provides business process orchestration, message transformation and business activity monitoring through designers and visual tools, while WCF provides a unified framework for building secure, reliable, transacted Web services, the paper said.
In addition, BizTalk and WCF will be tightly integrated in future versions. The next release of BizTalk Server will feature a WCF adapter that will enable developers to incorporate WCF services into business process orchestrations, the paper said. Microsoft has developed an early version of the adapter.
"Just as ASMX [ASP.Net for Web services] and WSE [Web Services Enhancements] provide BizTalks Web services capabilities today, subsequent releases of BizTalk will build directly on WCF to provide secure, reliable, transacted Web services support as a core component of BizTalk," the paper said.