Web Services - Summary.
Web service standards are used to develop client/server applications on the Internet.
The standards recognise the service provider and client components central to the client/server model. They also identify additional servers. Registry servers contain details about available services. These details are published by service providers and discovered by clients. Security servers provide authenticity assertions about clients.
Web service protocols are based on XML messaging. The SOAP protocol allows clients to execute methods on remote servers. This applies to the client/server application, the registry interface (UDDI) and the security server interface (SAML).
Before the web service standards were available, the client/server interfaces were developed on an ad-hoc basis. The use of XML and SOAP provides reusable libraries of code for building and parsing messages. The provision of UDDI servers encourages the reuse of application interfaces, allowing for the development of application standards and reducing the amount of client software that needs to be developed.