A Web service description contains abstract representations of
the input and output messages used by the Web service. WebSphere Message Broker uses
the Web service description to construct the data structures used by application
programs. At run time, WebSphere Message Broker performs
the mapping between the application data structures and the messages.
The description of a Web service contains, among other things:
- One or more operations.
- For each operation, an input message and an optional output message.
- For each message, the message structure, defined in terms of XML data
types. Complex data types used in the messages are defined in an XML schema
which is contained in the <types> element within the Web
service description. Simple messages can be described without using the <types> element.
WSDL contains an abstract definition of an operation, and the associated
messages. WSDL cannot be used directly in an application program.
To implement the operation, a service provider must do the following actions:
- Parse the WSDL, in order to understand the structure of the messages.
- Parse each input message, and construct the output message.
- Perform the mappings between the contents of the input and output messages,
and the data structures used in the application program.
A service requester must do the same in order to start the operation.