SOA has received its fair share of interpretations. It is a term that is commonly bandied about without clear definition. In fairness, the topic of SOA is probably as much about cultural change as it is about concepts and techniques. However, SOA is integral to the approach described in this book and therefore it is important to define our terms very clearly.

Part 3 of this book lays out the two major aspects of the SOA: policy and structure. We explain how to achieve an integrated approach to SOA that is driven top-down by the BA, and equally that is supported bottom-up by SOM.

Chapter 7 sets the context for the remainder of part 3 by providing an overview of SOA concepts and shows how the essentially static view of the SOA interconnects with the dynamic view of run-time services provided by the SOM. This paves the way for our discussion of SOM in part 4. We also provide an overview of the required changes in mind-set.

Chapter 8 deals with the policy aspect of SOA and provides techniques for the business–IT alignment of policy. We provide an overview of the four main areas of SOA policy – QoS, design, sourcing and usage, and technology – and preview the four key types of QoS requirement – agility, capacity, availability, and security.

Chapter 9 centers on agility, and provides a compendium of service design techniques for structuring the SOA and ensuring business–IT alignment.