Here I give the definition of a service in SOA.
What is the service SOA type?
A service is the most fundamental unit of service-oriented logic, a basic building block of the service oriented computing platform. Because of the enterprise-centric characteristic a service is an enterprise resource. A service is a physical independent software program with distinct design characteristics (achieve strategic goals). A service has a functional context and a set of capabilities, which are exposed by a service contract.
A unit of solution logic is called a service, if service-orientation has been applied to a meaningful extent. Service oriented solution logic is compromised of many services that form a service composition. Services are designed in a specific manner and delivered via a specific lifecycle.
- granularity (service, capability, data and constraint granularity)
- contract design
- agnostic vs. non-agnostic
- legacy encapsulation