Basic principles

We have emphasized that the SOA evolves over time in coordination with the business process redesign efforts. Now it is time to take a closer look at the concept of SOA itself. Unfortunately, SOA has become a much overused and abused term, subject to vague interpretations. It is important to clarify what exactly is involved in the idea of an SOA and how it differs from previous approaches to IT architecture. In this short chapter, we therefore provide an overview of the elements of SOA and outline the overall approach to evolving the SOA.

It is probably fair to say that the topic of SOA is as much about attitudes and cultures as it is about concepts. Apart from the shifts already discussed in the BA area, there are some other major shifts in mind-set required, that we discuss in this chapter.

While the SOA helps to plan strategies and specify services, the software has to work, and work extremely well in demanding conditions. Enter, therefore, SOM. In this chapter, we elaborate on the concept of SOM (introduced back in 2.3) and outline its relationship to the SOA. Later in this book, we shall build upon these introductory guidelines.

The elements of the SOA

What exactly, then, is the SOA? In this section, we provide the short answer in terms of a high-level bill of materials. There are two major aspects of the SOA: policy and structure.

The policy aspect of SOA falls into four parts:

• QoS

• Design

• Sourcing and usage

• […]