A brilliant introduction to SOA by Dan North:

During the past few years, service-oriented architecture (SOA) has become a mainstream approach for designing and developing enterprise software. As with most new technologies, the adoption of SOA has been led by software vendors and shaped by their particular tools and sales targets. Naturally it is in the vendors’ interest to emphasize the complexity of SOA and then provide a timely and profitable solution. This leads many systems architects into a technology-centric view of SOA, when, in fact, the most important criteria for a service-oriented architect — before tackling the technology — should be a keen understanding of the business.