Originally inspired by techniques used to design buildings and cities, and popularized by the Gang of Four during the mainstream emergence of object-orientation, design patterns have seen us through the various shifts in architecture, technology, and, of course, design. Pattern catalogs have periodically emerged, one building on the other, and each revealing a set of problem-solving techniques and providing invaluable insights as to how and when those techniques should be used to help us attain our design goals.

SOA has its own history, having risen out of a haze of ambiguity to establish itself as the basis of a distinct and maturing distributed computing platform with a distinct and ambitious design paradigm in its own right.

And now, finally, these worlds converge. SOA and service orientation (and surrounding technology platforms) have matured to the extent that proven design practices have surfaced for use by the masses. Subsequent to years of research, reviews, and validation, this body of work has been formally documented as a comprehensive collection of over 90 SOA design patterns.

One of the most intriguing aspects of the SOA design pattern catalog is its breadth. We have patterns providing design techniques that range from adjusting minute validation logic in a service contract to design strategies that help us structure pools of services across an entire enterprise.

This scope is indicative of the enterprise-centric focus of service-oriented computing in general. When carrying out an SOA initiative, we need to pay attention to many design details with every service we deliver, while always keeping the big picture in our sights. Design patterns support us in maintaining this balance by helping us overcome common obstacles that have historically inhibited or even derailed SOA project plans.

Each pattern is like a piece of wisdom resulting from the trials and errors of pioneers and the sweat and tears (and therapy) that sometimes accompanied those early SOA project experiences. So, please, a moment of silence for those who have suffered so that we can now benefit...

All right then, without further ado, let's introduce the SOA design patterns.

Patterns in a Service-Oriented World
Service-oriented computing has a specific set of strategic goals and benefits associated with it. Most of these goals, such as increasing agility and ROI, are well known, as is the fact that to attain these goals, you need to design your solutions by following service orientation, a distinct design approach tailored to support service-oriented computing.

There's a close relationship between the service-oriented architectural model and the service-orientation design paradigm. It is through the application of service-orientation design principles that you end up creating software programs that are legitimately "service-oriented." When you implement SOA as a technology architecture you establish an environment that is conducive not just to enabling the creation of effective service-oriented solutions, but also to enabling the effective long-term governance and evolution of the individual services that can be composed and recomposed to comprise these solutions.