14.3 WSDL

WSDL ^[7] is essentially an XML interface definition language (IDL) that provides a way to describe the function and the interface of a service. An IDL is an XML format for describing network services as a set of end points operating on messages containing either document-oriented or procedure-oriented information. The operations and the messages are described abstractly and then bound to a concrete network protocol and message format to define an end point. Related concrete end points are combined into abstract end points, or services. WSDL is extensible to allow the description of end points and their messages regardless of what message formats or network protocols are used to communicate. However, the only described bindings are for SOAP V1.1 and the HTTP GET and POST methods .

^[7] See http://www.w3.org/TR/wsdl.

The WSDL service information can be extracted from a UDDI business service entry or may be obtained from other service repository sources. Regardless of the source, both the runtime and development tools can use WSDL to determine runtime bindings to a service. This information can be used to build the logic to access the service either directly from the client or through generated code stubs.

WSDL has the potential to be extended ^[8] to consider the definition of the context needed by a business's execution environment. This includes the business's security. Without these extensions, people will make assumptions about security in the runtime environment of a Web service. However, if these security assertions are defined in terms of XML, it will be possible to have a common interpretation of the security attributes in different implementations and begin to allow the full description of the Web service to be discovered , as described in the Web Services Policy Framework specification (WS-Policy).

^[8] See http://xml.coverpages.org/wsfl.html.