Driving the Enterprise Service Bus

It's a bird, it's a plane, it's a bus -- an Enterprise Service Bus!

In a world where Web services-based technologies are the heroes of application development, ESB is grabbing headlines.

But while vendors have variously detailed visions of Superman-like grandeur, the technology signals one of the most significant milestones in Web services' evolution.

Variously called ESB or message broker, the technology uses Web services and message queuing to facilitate the development of flexible, SOA (services-oriented architectures).

The term ESB, while not fully embraced in all circles, is originally attributed to a report by Stamford, Conn.-based Gartner. The technology uses industry-standard specifications such as SOAP or JMS (Java Message Service) to create loosely coupled architectures based on interfaces and flexible programming requirements. In this paradigm, applications are merely services, not the monolithic, difficult-to-integrate systems of the past.

Gartner analyst Jess Thompson said in a report that ESB is "a class of integration software that came to market in 2002 and is intended to support the deployment of Web services. An ESB combines messaging, basic transformation, and content-based routing."

Mark Bauhaus, vice president of Java Web services at Sun Microsystems in Palo Alto, Calif., observes that ESB has evolved from message-queuing technology, which was originally point-to-point in nature. "Now it's started to take on some of the Web services using XML," he said.

It's therefore not surprising that the pundits increasingly refer to ESB as a method of making application integration simpler and cheaper, particularly for smaller organizations.

Opportunities are emerging as companies of all sizes increasingly view mainstream EAI technologies as too expensive. This standards-based approach to service-oriented architectures is gaining favor over competing methodologies such as CORBA, Java, or Cobol-based integration, observes Rob Hailstone, an analyst at IDC in Framingham, Mass.

Yet ESB's road to corporate stardom is no rose-petal-covered path. Before it reaches a significant level of maturity, the industry must resolve fundamental debates such as the correct definition and notion of what ESB should achieve.

For example, emerging vendors including Sonic Software, Blue Titan, and Cape Clear have embraced ESB, with Sonic going so far as naming a product Enterprise Service Bus.

On the other hand, IBM and Microsoft don't view ESB as a specific product, choosing instead to concentrate on the notion of a SOA.

"I think about [SOA] as a mindset evolution for IT about the way [to] architect solutions," says Steven VanRoekel, director of Web services marketing at Microsoft in Redmond, Wash. "There will be different sets of guidelines on how to think about writing applications really as a service instead of as a point solution to make them extensible for the future," says Steve Holbrook, IBM program director of emerging e-business standards.

"In many ways [service-oriented architectures are] parallel to the Web. [They] allow us to have a Web-like relationship between companies across the Internet," Holbrook adds.