WebServices dot org

Whither the ESB?

Does ESB = SOA?

Adoption of Service Oriented Architectures (SOA) has been steadily increasing for the past few years, and actual implementations are now at a sizable number as well. With a help from a few well established vendors, the Enterprise Service Bus (ESB) has been promoted as the focal point of many SOA conversations during this time.

There are good reasons for this initial association. An ESB can provide important enterprise requirements including guaranteed message delivery and integration to back-end applications.

Every technology since the dawn of enterprise computing has had to meet these requirements before being deployed in mission-critical applications. Think midrange computers, client server and internet technologies, just to name a few. These were not deployed widely in enterprise IT shops until reliability, scalability, and the other abilities were in place, and widespread adoption of SOA is no different.

The ESB’s core technology, however, was not built for SOA. It was built for a different purpose. ESBs started their lives as EAI (Enterprise Application Integration) or message queues, designed to handle integration and messaging. Web service standards were added at a much later date. So ESBs support some of the standards used by SOA, but on top of the traditional architecture.

What is a SOA and Where is it Going?

So what, then, is a SOA? “Service Oriented” isn’t really the same thing as “Bus Oriented.” SOA is meant to be distributed and requires technology to fit that goal. The technologies and products built specifically for SOA have matured to the point where they are being used in mission-critical enterprise applications, and can leverage existing technology investments (that was the whole point of services, wasn’t it?). So where does the ESB fit?

Whither the ESB?

Reports of the ESB’s decline have been exaggerated, but its role will be redefined. An ESB can be a great way to deliver messages reliably from point A to B (among other things), but it isn’t best suited to serve as the cornerstone of an SOA implementation – there are enterprise-ready alternatives that are designed specifically for SOA that enable greater realization of the true goal of implementing an SOA.

The Service Component Architecture (SCA) ( www.osoa.org ) and Microsoft’s WCF are both good examples of reference architecture for an SOA. There is now product available from multiple vendors, with both commercial and open source options available for SCA.