Microsoft has its own approach to implementing SOA. Termed as the middle out approach, the basics behind it is to provide a balance between the Top down (too much design) and the bottom up (scattered implementations). It suggests that an organization starts off with a small portion of the business and make it service oriented thereby proving the beneifts and potential to the stakeholders, once this is succussfull scale it out to other processes in the organization.
There are three phases in the middle out approch:
1. Expose: Identify legacy apps, products and expose them as services.
2. Compose: Compose the various apps. in the organization into orchestractions using workflow etc.
3. Consume: Create disparate clients to consume these services.