A service-oriented architecture (SOA) is a distributed software architecture that consists of multiple autonomous services. The services are distributed such that they can execute on different nodes with different service providers. With a SOA, the goal is to develop software applications that are composed of distributed services, such that individual services can execute on different platforms and be implemented in different languages. Standard protocols are provided to allow services to communicate with each other and to exchange information. In order to allow applications to discover and communicate with services, each service has a service description, The service description defines the name of the service, the location of the service, and its data exchange requirements (Erl 2006, 2009).

A service provider supports services used by multiple clients. Usually, a client will sign up for a service provided by a service provider, such as an Internet, email, or Voice over Internet Protocol (VoIP) service. Unlike client/server architectures, in which a client communicates with a specific service provided on a fixed server configuration, this chapter describes SOAs, which build on the concept of loosely coupled services that can be discovered and linked to by clients (also referred to as service consumers or service requesters) with the assistance of service brokers.