Web Services Description Language Version 1.1 and 2.0
Web Services Description Language (WSDL) is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information.
The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete end points are combined into abstract endpoints (services).
WSDL is extensible to allow the description of endpoints and their messages regardless of what message formats or network protocols are used to communicate. The WSDL 1.1 specification only defines bindings that describe how to use WSDL in conjunction with SOAP 1.1, HTTP GET and POST, and MIME.
WSDL 2.0 provides a model as well as an XML format for describing web services. It enables you to separate the description of the abstract functionality offered by a service from the concrete details of a service description, such as "how" and "where" that functionality is offered. It also describes extensions for Message Exchange Patterns, SOAP modules, and a language for describing such concrete details for SOAP 1.2 and HTTP. The WSDL 2.0 specification also resolves many technical issues and limitations that are present in WSDL 1.1.
The specification for WSDL 1.1 is published by the World Wide Web Consortium (W3C) as a W3C Note at WSDL Version 1.1.
The specification for WSDL 2.0 is published as a W3C recommendation at WSDL Version 2.0.