Although SOA will make it possible for business parties to achieve agility, SOA itself is technically not simple to implement. In some cases, it even makes software development more complex than ever, because with SOA you are building for unknown problems. On one hand, you have to make sure that the SOA blocks you are building are useful blocks. On the other, you need a framework within which you can assemble those blocks to perform business activities.

The technology issues associated with SOA are more challenging than vendors would like users to believe. Web services technology has turned SOA into an affordable proposition for most large organizations by providing a universally-accepted, standard foundation. However, web services play a technology role only for the SOA backplane, which is the software infrastructure that enables SOA-related interoperability and integration.

The following figure shows the technical complexity of SOA. It has been taken from Gartner, Twelve Common SOA Mistakes and How to Avoid Them, Publication Date: 26 October 2007 ID Number: G00152446.

As Gartner says, users must understand the complex world of middleware, and point-to-point web service connections only for small-scale, experimental SOA projects. If the number of services deployed grows to more than 20 or 30, then use a middleware-based intermediary— the SOA backplane. The SOA backplane could be an Enterprise Service Bus (ESB), a Message-Oriented Middleware (MOM), or an Object Request Broker (ORB). However, in this book, we will not cover it. We will build only point-to-point services using WCF.