The entire history of software engineering can be characterized as one of rising levels of abstraction. We see this in our languages, our tools, our platforms, and our methods. Indeed, abstraction is the primary way that we as humans attend to complexity—and software-intensive systems are among the most complex artifacts ever created.

I would also observe that one of the most important advances in software engineering over the past two decades has been the practice of patterns. Patterns are yet another example of this rise in abstraction: A pattern specifies a common solution to a common problem in the form of a society of components that collaborate with one another. Influenced by the writings of Christopher Alexander, Kent Beck and Ward Cunningham began to codify various design patterns from their experience with Smalltalk. Growing slowly but steadily, these concepts began to gain traction among other developers. The publication of the seminal book Design Patterns by Erich Gamma, John Vlissides, Ralph Johnson, and Richard Helm marked the introduction of these ideas to the mainstream. The subsequent activities of the Hillside Group provided a forum for this growing community, yielding a very vibrant literature and practice. Now the practice of patterns is very much mainstream: Every well-structured software-intensive system tends to be full of patterns (whether their architects name them intentionally or not).

The emerging dominant architectural style for many enterprise systems is that of a service-oriented architecture, a style that at its core is essentially a message passing architecture. However, therein are many patterns that work (and anti-patterns that should be avoided).

Thomas’ work is therefore the right book at the right time. He really groks the nature of SOA systems: There are many hard design decisions to be made, ranging from data-orientation to the problems of legacy integration and even security. Thomas offers wise counsel on each of these issues and many more, all in the language of design patterns. There are many things I like about this work. It’s comprehensive. It’s written in a very accessible pattern language. It offers patterns that play well with one another. Finally, Thomas covers not just the technical details, but also sets these patterns in the context of economic and other considerations.

SOA Design Patterns is an important contribution to the literature and practice of building and delivering quality software-intensive systems.

—Grady Booch, IBM Fellow

September, 2008