A software component that publishes its interface on and responds to requests from a network, in particular the Internet. web services use open XML-based standards: interfaces are published using WSDL (Web Services Description Language), and services usually communicate with their clients through SOAP messages. The ambition of web services is to use the Internet to implement large-scale distributed processing in an open way.

http://www.w3.org/2002/ws/ The WC3’s Web Services Activity Page

http://www.w3.org/TR/wsdl20-primer/ The WSDL (version 2.0) specification primer