The <message> element describes the data being exchanged between the web service providers and the consumers.
- Each Web Service has two messages: input and output.
- The input describes the parameters for the web service and the output describes the return data from the web service.
- Each message contains zero or more <part> parameters, one for each parameter of the web service function.
- Each <part> parameter associates with a concrete type defined in the <types> container element.
Let us take a piece of code from the WSDL Example chapter −
<message name = "SayHelloRequest"> <part name = "firstName" type = "xsd:string"/> </message> <message name = "SayHelloResponse"> <part name = "greeting" type = "xsd:string"/> </message>
Here, two message elements are defined. The first represents a request message SayHelloRequest, and the second represents a response message SayHelloResponse.
Each of these messages contains a single part element. For the request, the part specifies the function parameters; in this case, we specify a single firstName parameter. For the response, the part specifies the function return values; in this case, we specify a single greeting return value.