WSDL is an XML notation for describing a Web service. A WSDL definition tells a client how to compose a Web service request and describes the interface that is provided by the Web service provider.
The WSDL document defines a service in terms of a number of ports (WSDL 1.1) and endpoints (WSDL 1.2), which define where the service is available.
Each named port or endpoint also defines a mechanism for accessing it: a binding. Each supported protocol has a separate binding; for example, SOAP over HTTP. Each binding refers to a named portType (WSDL 1.1) and interface (WSDL 1.2).
A binding defines the message wire format and transport details.
A portType or interface is the logical interface to the Web service.
Both the binding and the portType or interface define operations.
Each operation comprises input and output elements that are defined in terms of messages or message parts.
The optional parameterOrder attribute is applicable only for RPC-style WSDL. The value of the parameterOrder attribute is an ordered list of WSDL message parts that provide a hint to a Web service provider about how the parts map to a method signature.
The message elements define a logical message in terms of one or more parts. Each part might correspond to a parameter on a method call.
A part is defined either as an XML Schema element or as an XML Schema type.
Web Service Description Language (WSDL)is a W3C specification which defines XML grammar for describing Web Services.XML grammar describes details such as:-
1. Where we can find the Web Service (its URI)? 2. What are the methods and properties that service supports? 3. Data type support. 4. Supported protocols.