A brief history of SOA

That's a big question and to answer it properly would require a great deal of detail. However, in a nutshell, the notion of a service-oriented architecture has been bouncing around the world of IT for several years and only really caught the eye of major software vendors with the emergence of the Web services technology platform. Early models provided more primitive definitions of what constituted an SOA; often the primary criteria was the involvement of a service registry and a discovery process. Since then, SOA has become a sophisticated and refined architectural model closely tied to a distinct design paradigm called service-orientation.

There are several characteristics that distinguish service-orientation from past design approaches such as object-oriented design, the foremost of which is an unprecedented emphasis on long-term, strategic benefit and ROI. As a result, the primary SOA transition motivators are driven by the need to harmonize and streamline enterprise environments while working toward a state where more and more business requirements can be fulfilled through the recomposition of existing services. It is important to understand these strategic goals (as well as the design characteristics required on a service-by-service basis to achieve them) in order to understand the difference between SOA as an architectural model and Web services as an implementation option for services. (If you are interested in learning more, Chapter 4 of "Service-Oriented Architecture: Concepts, Technology, and Design" documents the history of SOA and compares it to past architectural models.)