What Is a Reusable Service?
One way of defining a reusable service is by the principles to which it adheres. Chief among those are the SOA principles that are the foundation for all SOA architectures. While a variety of patterns and practices may be applied to the development and use of services, those foundational SOA principles are independent of the implementations, protocols, standards, and technologies that may be used within a service-oriented architecture. The use of standards is important for reuse (through interoperability), but those standards alone can't guarantee reuse. Those fundamental SOA principles have been widely recognized and adopted, but it is good to go through them again (and again).