Descriptions and management policies
SOA architecture - XML infrastructure

Web Services Description Language, or WSDL, a W3C recommendation, is an XML format for describing a network service as a collection of nodes ("endpoints") capable of processing messages containing either documents or requests to execute procedures. WSDL has been designed without any preconditions as to the nature of the messages or the type of transport used (WSDL can be extended to take account of specific formats). However, version 1.1 of the standard specifies that WSDL can only be linked to SOAP, HTTP and MIME. With SOAP, WSDL enables XML middleware to be implemented directly on top of the Web's HTTP 1.1 protocol, and as such forms the basis of Web services architecture, thus embodying the W3C version of SOA.