Web services can also be used to implement Service-oriented architecture (SOA). SOA is a collection of services that mutually communicate one another, where the basic unit of communication is a message, rather than an operation. It is also called message-oriented services.
XML schema that is also known as XSD usually defines the service, which SOA communicates. Mostly the bigger software vendors and industry analysts support SOA service and maintain it by registry that functions like a directory listing. Applications can found and access the services.
Representational state transfer
Representational state transfer (REST) is a pattern of software architecture used for getting information content from a Web site by reading a designated Web page containing an XML file, which describes and includes the desired content. Sometimes, REST has been used to specify any simple interface that passes on domain-specific data over HTTP without any extra messaging layer like SOAP or session tracking via HTTP cookies.