Cutting slices from a blob

I liked the way Mats Helander described service-orientation. To understand the good thing about SOA you really need to see it from the business perspective. From a 10000' view, IT really looks like a big blob. On a 1000' view, you can discern smaller blobs which are applications (aka black boxes or silos). The SOA will help breaking up the applications in small services that can be composed into new services based on policies. The selection for how the services will be used in a composition is up to the heart of the SOA - the mediation layer. The mediation layer (such as WCF or Synapse) will make sure that the policies are applied correctly.

Some people claims that service composition (orchestration) is part of the SOA paradigm. I would rather give credit to BPM for techniques related to service composition.