A web service is a software application that is uniquely identifiable via a Uniform Resource Identifier (URI) and whose interfaces can be defined, described and found as XML artifacts. A web service supports direct interaction with other software agents using XML-based messages via the exchange of internet-based protocols. Web services allow the service provision and business transactions via the internet by allowing an application to access the web service provided by the service provider.
The service and the application communicate via SOAP (Simple Object Access Protocol). SOAP is a network protocol that allows data exchange between systems and the execution of remote procedure calls. SOAP is based on the services of other standards: XML for the representation of data and internet protocols of the transport and application layer for the transmission of the messages. The most common combination is SOAP via HTTP and TCP.