What is a web service?

A web service is 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 (that detail the operations), transport protocols, and location.

The nature of the interface hides the implementation details of the service so that it can be used independently of the hardware or software platform on which it is implemented and independently of the programming language in which it is written.

This independence allows and encourages web service based applications to be loosely coupled, component oriented, cross-technology implementations. web services can be used alone or with other web services to carry out a complex aggregation or a business transaction.