Most organizations considering or in the midst of deploying a service-oriented architecture (SOA) are familiar with the concept or even the many varied definitions of the term enterprise service bus (ESB). In fact, ESBs are becoming a critical part of an SOA.

2/18/2005 By Stephen Todd, Master Inventor, IBM Academy of Technology, IBM

Interestingly, Gartner just released data stating that more than half of all large enterprises will have at least the core of an ESB running by year-end 2006. The rising interest in ESBs is based on their ability to increase scalability, ease of change and quality of service for large and frequently changed SOA and event-driven architectures.

With the anticipated increase in ESB deployments as well as the rise in SOAs, the following takes a look at the role of Web services in an ESB.

An ESB, as we know, is an architectural pattern that enables you to optimize the distribution of information between different types of applications across multiple locations. The ESB pattern is founded on and unifies message-oriented, event-driven and service-oriented approaches to integration.

Providing connectivity and integration for Web services-focused applications and services, the core characteristics of an ESB provide:

• Standards-based application integration
• Support for Web services, message-based transport and publish-and-subscribe (event-based) integration
• Transformation
• Intelligent routing

Still, it is important to understand the following points about ESBs:

• The term enterprise does not necessarily have to encompass the whole of an organization. One of the attractions of an ESB is that you can start small, perhaps with only two to three physical instances and expand to fit evolving business circumstances.
• The term bus is used to convey the notion of information being carried between originators and receivers, using different communications models and data formats, to many different destinations. The bus provides a common backbone through which applications can interoperate.
• An ESB should possess some degree of programming intelligence to determine routing or persistence, or to implement rules or content processing.

An ESB introduces new options for interoperation and helps enable information to flow to the people who need it, when they need it. In this way, an ESB can improve the responsiveness and accuracy of decision making.

What should an ESB deliver?

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