WSDL is one of the three primary components of web services. It is a standard that defines service interfaces.

"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."

WSDL descriptions contain:

• Types: a container for data type definitions using some type system (such as XSD).
• Message: an abstract, typed definition of the data being communicated.
• Operation: an abstract description of an action supported by the service.
• Port Type: an abstract set of operations supported by one or more endpoints.
• Binding: a concrete protocol and data format specification for a particular port type.
• Port: a single endpoint defined as a combination of a binding and a network address.
• Service: a collection of related endpoints.

WSDL 1.1 is currently the most commonly used version and is a part of the WS-Basic Profile.

See: WSDL 1.0, WSDL 1.1, WSDL 1.2