WSDL document
WSDL is a metalanguage used for describing the offered functions, data, data types, and exchange protocols of a Web service. WSDL mainly defines the operations that are externally accessible, as well as the parameters and return values of these operations. Specifically, a WSDL document contains functional details about:
the interface
the access protocol and details for deployment
all information required to access the service in machine-readable format.