A web service is any piece of software that makes itself available over the internet and uses a standardized XML messaging system. XML is used to encode all communications to a web service. The basic web services platform is XML + HTTP. All the standard web services work using the following components SOAP, UDDI and WSDL.
Advantages of web services
The idea of a web service developed from the evolution of the Internet. The intent behind a web service is to drive the Internet as a transactional tool rather than simply a visual tool. These application-to-application interactions are driven by, and built on, existing standards such as:
Extensible Markup Language (XML)
Hypertext Transfer Protocol (HTTP)
Universal Description, Discovery, and Integration (UDDI)
Web Services Description Language (WSDL)
The standardized nature of the pieces that implement a web service solve many problems related to intersystem communication.