This book is all about designing and developing service-oriented applications using WCF—yet there is considerable confusion and hype concerning what service-orientation is and what it means. To make matters worse, most of the vendors in this space equate their definition of service-orientation with their products and services. The vendors (Microsoft included) add to the confusion by equating service-orientation with high-end Enterprise applications, where handling high scalability and throughput is a must (mostly because they all contend for that market, where the business margins are made).

This appendix presents my understanding of what service-orientation is all about and attempts to put it in a concrete context. My take is different from that of the large vendors, but I believe it is more down-to-earth, rooted as it is in trends and the natural evolution of our industry. As you will see, I believe that service-orientation is not a breakthrough or a quantum leap of thought, but rather the next gradual step (and probably not the last step) in a long journey that spans decades.

To understand where the software industry is heading with service-orientation, you should first appreciate where it came from. After a brief discussion of the history of software engineering and its overarching trend, this appendix defines service-oriented applications (as opposed to mere architecture), explains what services themselves are, and examines the benefits of the methodology. It then presents the main principles of service-orientation and augments the abstract tenets with a few more practical and concrete points to which most applications should adhere. Finally, the appendix concludes with a look to the future.