Just what is an ESB, anyway?

Enterprise Service Bus (ESB) technology has sparked a debate in the integration space. Players in the ESB arena agree this newfangled technology is critical in providing a mechanism for application integration in service-oriented architectures (SOAs). However, vendors do not agree on whether an ESB is an actual product or merely a concept, even though various providers are selling software that they have labeled an ESB.

Sonic Software, which has been credited with coining the term Enterprise Service Bus, and Cape Clear Software both fall into the category of those productizing ESBs, while webMethods and IBM view an ESB as merely one technology piece in the middleware stack. Sonic and Cape Clear will be joined by BEA Systems this summer, when the company introduces its ESB product, code-named Quicksilver.

"An ESB simplifies the integration and flexible reuse of business components using a standards-based SOA," said Dave Chappell, vice president and chief technology evangelist at Sonic.

"Right now, there's a huge demand for ESBs, so we’ll more than double again [in sales] this year," said Annrai O'Toole, CEO of Cape Clear. The privately held company has revenues in the tens of millions and more than 200 ESB customers since introducing its product four years ago, O'Toole said.

Noting the high interest in ESB technology, O'Toole acknowledged that Cape Clear has been approached about being acquired. But the company prefers to remain independent.

 "This is a hot space. This is the next generation of middleware platforms," O'Toole said.

Sonic officials also boast a customer base of about 200 users but would not comment on any outside interest in acquiring Sonic.

WebMethods maintains its contrary view on the ESB.

 "We don't necessarily look at ESB as a product but as a set of capabilities," for communication and mediation, Rick Clements, director of strategic marketing at webMethods, said. The company sells as its ESB solution its Enterprise Services Platform, featuring a set of technologies for communications, data transformation and routing, and service-level monitoring.

An ESB uses Web services-based systems integration but can support other technologies as well, such as Java Message Service and even EDI-type communications, vendors said. The technology represents an alternative to more expensive hub-and-spoke integration, said Eric Newcomer, CTO at Iona Technologies, which offers its Artix ESB.

"We define it as a vertical bus that connects end-points together using network protocols and applications and languages that already exist in the enterprise," Newcomer said. "We view it as an incremental technology rather than a foundational technology."

The ESB concept itself is subject to multiple definitions, said Shawn Willett, principal analyst at Current Analysis. "The problem with the ESB market is that people define it differently," Willett said. "I think it's a difficult market because some of the big players don't see an ESB as a product per se; they just see it as an architectural element." Willet places himself amongst those who believe an ESB is, indeed, a product.

An ESB, Willett said, can be defined as a lower cost option for integration that is reliant on Web services standards and endpoints. But do you need to deploy an ESB when setting up an SOA?

"I think if you want to do it right, you do," Willett said.