Web Service

A software system that supports interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically, web Service Definition Language, or WSDL). Web services fulfill a specific task or a set of tasks. A web service is described using a standard, formal XML notion, called its service description, that provides all of the details necessary to interact with the service, including message formats, transport protocols, and location.