What is the difference between service-oriented architecture (SOA) and service-oriented integration (SOI)?
SOA is an architectural pattern for constructing systems, based on service descriptions. Such systems are rarely constructed in completely new IT environments; instead, many of the services must come from existing applications within an enterprise. The act of adapting an application (or messaging protocol) to interact with other applications that it was not designed to interoperate with is called integration. Adapting applications and protocols to a SOA is a very common activity, and is called service-oriented integration (SOI).