Web services applications - WSDL

WSDL

WSDL stands for Web Services Description Language and is an XML-based language that is defined by the W3C for describing an interface between applications.

A WSDL definition tells a client how to compose a Web services request and describes the interface that is provided by the server.

service

The WSDL document defines a service in terms of a number of:
  • ports (WSDL 1.1)
  • endpoints (WSDL 1.2)
These define where the service is available.

ports/endpoints

Each named port also defines a mechanism for accessing it – a binding. There is a separate binding for each supported protocol; for example, SOAP over HTTP. Each binding refers to a named:
  • portType (WSDL 1.1)
  • interface (WSDL 1.2)

bindings and portTypes/interfaces

  • A binding defines the message wire format and transport details.
  • A portType/interface is the logical interface to the Web service.

Both binding and portType/interface define operations.

operations

Each operation comprises input and output elements defined in terms of messages or message parts.

The optional parameterOrder attribute is only applicable for rpc-style WSDL. The value of the parameterOrder attribute is an ordered list of WSDL message parts providing a hint to a Web service provider about how the parts map to a method signature.

message elements

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.

These elements and types are fully defined by either or both of the following:
  • a WSDL <types> section
  • imported schema (.xsd) files that provide the definitions for the WSDL part definitions.

More information

See the W3C at: http://www.w3.org and in particular the WSDL 1.1 document at: http://www.w3.org/TR/wsdl.

See the WS-I at: http://www.ws-i.org/ and in particular the WS-I Basic Profile under http://www.ws-i.org/deliverables.

Related concepts
Message flows overview