It's 2006: what's an 'ESB'?

Just about every vendor sells one. Some enterprises have several. But ESB continues to be a term in search of a meaning. Earlier in July, I posted details about Forrester's latest rankings of ESB vendors, in which both BEA and Cape Clear claimed the number one spot.

However, there is considerable contention in the industry about exactly what an "enterprise service bus" is, and at least one industry executive questions Forrester's definition used in the ratings.

In a new post, Eric Roch, chief technologist for Perficient Inc., wonders out loud about Forrester's definition of an "ESB":

"The problem I have with this report is the narrow focus. What is an ESB anyway? There is no formal industry standard. I don't disagree with Forrester's definition, except for the fact that it eliminated many software vendors that should be considered for a company's ESB functionality in their SOA."

In the report, Forrester defined an "ESB" as "infrastructure software that makes reusable business services widely available to users, applications, business processes, and other services." This is actually an extremely broad definition, and Forrester admits as much, noting that there is a lot of overlap between ESB and other various product types:

"...segments of the Web services infrastructure market also include security, management, and registry features, some of which are also now delivered by ESBs. This ferment of Web services infrastructure technologies is still bubbling and spawning a variety of solution types, from appliances, to ESBs, to combined solutions for managing and securing Web services-based exchanges. The boundaries between these segments are continuing to move and are unlikely to settle down for another few years."

Thus, Roch finds it puzzling that some major players, such as TIBCO and IBM were either eliminated or received relatively low rankings. Roch, who used to work for TIBCO, observes that TIBCO is nicknamed "The Bus Company," and has "been doing messaging much longer than anyone else and for some of the largest companies in the world."

He goes on to observe that "TIBCO was eliminated because they don't have a pure-play ESB product. But they can provide all the functionality in Forrester's ESB definition with their product stack - the registry is OEM but so is BEA's." He also notes that IBM scored low because Forrester evaluated IBM's standalone ESB product, "but the ESB product is an entry level product that is extended with MQ, Message Broker, WBI Modeler and Process Server." IBM and TIBCO also have strong business process optimization stories associated with their products, Roch points out, which is what SOA is all about at the end of the day.

Alas, while most vendors (except Microsoft) have jumped on the ESB bandwagon, we still really can't agree on exactly what an ESB is. And, as Roch points out, attempts to categorize it end up missing the mark.