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.

An SOA is usually defined as an IT architecture that links loosely coupled, easily changeable services based on standards such as Web services.

One believer in the ESB is Rotech Healthcare, an Orlando, Fla.-based company that offers respiratory medicines and home medical equipment. Rotech uses Sonic ESB to integrate Web-based and legacy systems and to tie databases into the company"s SOA, said Albert Prast, CIO of Rotech.

Using an ESB makes it easier to build applications that depend on one another without using older technologies such as ftp, Prast said. The ESB provides the glue in a system that uses predefined objects that hand packets of data from one system to another while ensuring transactional integrity, he said. "It allows you to create reusable components that are well-defined, well-documented, secure, and very, very reliable," Prast said.

BEA is a believer as well. "It"s a core infrastructure for an SOA," said Kelly Emo, senior product marketing manager for the company"s Quicksilver project. The ESB provides a unification layer for dynamic mediation between services, she said.

The ESB connects service consumers to back-end service endpoints, sets up routing and transformation services and manages interactions, Emo said. This is unlike traditional integration, which required too much coding, she said.

"We"re seeing this as a rapidly growing market," Emo said.

BEA is promising that its ESB will be different than others because it is not focused on messaging and mediation, Emo said. The company, though, does not see an ESB as a requirement for an SOA. "[However], it makes it a lot easier," Emo said.

The Sonic ESB product offers messaging, mediation and control of interactions between services in an SOA, Chappell said. "Services in an SOA allow flexible interaction between reusable business components," he said.

"Messaging is a core component of an ESB, but there are other core components of an ESB that are equally important," such as service hosting and mediation between disparate data types, Chappell explained.

Cape Clear recently put out an online quiz portending to expose "counterfeit" ESBs. As might be expected, this marketing piece steered participants toward Cape Clear ESB.

"It"s definitely a clever marketing piece that wants to guide you in the direction that makes the true ESB point in the direction of the [Cape Clear] product," Chappell said.

"They [Cape Clear officials] say they don"t require a messaging product. That"s a funny way of saying they don"t have one," Chappell added.

Cape Clear, with its test, is attempting to clear up the confusion about what exactly is an ESB, O"Toole said. "There are lots of vendors pretending to be something they"re not," O"Toole said. He then lists vendors such as IBM, webMethods and, of course, Sonic as pretenders.

"[Sonic] may have invented the term. We"re delivering the product," O"Toole said.

Cape Clear"s Web services-centric focus is countered by IBM, which does not offer a specific ESB product but says its WebSphere MQ software participates with other products to form an ESB.

"I think there is an ESB in terms of a concept but there are some vendors that are trying to sell an ESB and saying all it needs to do is Web services and I think that is a narrow view of a bus," said Scott Cosby, program director for WebSphere business integration products at IBM.

There are tons of applications that either never will consume a Web service or will not do so for a while, Cosby said. Legacy applications such as CICS and other mainframe systems must be accommodated, he said.

At webMethods, the company believes an ESB is valid for integration scenarios involving basic communications and interoperability between Web services and applications, Clements said. "In more complex integration scenarios [such as integrating with partners], we think companies will look for more than just an ESB," said Clements.

Although Cape Clear said it supports EDI formats via Web services, Clements said ESBs do not actually support EDI. WebMethods provides support for a wide range of integration methods including EDI and RosettaNet.

Pricing on ESB products carry a broad range. Sonic ESB is priced from US$30,000 for a single installation of an SOA suite to $200,000 for a moderately sized deployment. Cape Clear ESB has a base price of about $25,000 per CPU, with a typical installation costing $50,000 to $100,000.

ESB user Prast cautioned that deploying an ESB can make your life more difficult in the beginning, because at Rotech it added a higher-level language for declaring variables. It also introduced new structures, procedures and documentation. And the upgrading alone is a time-consuming process. 

"We did it in a test environment first, but it"s not a piece of shrink-wrapped software that you just install and you"re done with," Prast said.