Myth #4: Pattern or Product: The term "Enterprise Service Bus" (ESB) is not really a product category; it is simply an abstract concept that can be applied toward a coupling of an existing application server and integration middleware.
An ESB is a highly distributable backbone upon which to build enterprise service-oriented architectures (SOA). Enterprises build service-oriented architectures, and an ESB is the backbone upon which to build it. As a result of the tumultuous disruption to the integration market caused by the advent of the ESB, some established integration vendors have laid down a smokescreen by saying that an ESB is simply an abstract pattern that can be overlaid across a composition of existing middleware and application server infrastructure that they already have. In fact, an ESB is definitely a coherent piece of infrastructure that you have been able to purchase from a number of vendors for at least a couple of years now. There are already dozens of ESB deployments in place across a variety of vertical industry segments including manufacturing, financial services, telco, and retail.

The definition of an ESB includes these basics:

• A distributed services architecture, which includes a lightweight container model for hosting integration components as remote services
• An enterprise messaging backbone that provides reliable delivery of messages between applications and services
• XML Data transformation
• Service orchestration and intelligent routing of messages based on their content
• A flexible security framework
• A management infrastructure that lets you configure, deploy, monitor, and manage your remote services

Myth #5: ESBs compete with the J2EE app server products.
An ESB is highly complementary to a J2EE app server. J2EE app servers can integrate well with other app servers, and with non-J2EE environments, by plugging into the ESB using standard interfaces such as JMS, MDB, JCA, or Web services.

Most adopters of ESB technology are also heavy users of application server technology. These customers use the combination of their application server and ESB as best-of-breed components in their integrated environment - the app server for hosting business logic and serving up Web pages in a portal server environment, and the ESB for integrating the app server with a variety of back-end applications and data sources across their extended enterprise.