Web Services Description Language (WSDL)

• Types define the data types used in messages. These types are often drawn from the XML Schema Language.
• Messages describe the part(s) of the input, output, and fault messages exchanged with the calling program.
• Operations provide a name for the action performed on messages.
• PortTypes group message(s) with operation(s).

Those WSDL documents for services deployed outside the WebLogic Server will include the concrete elements of the WSDL, which provide additional information about how and where to access the service:
• The binding describes how a given portType operation will be transmitted, such as HTTP or SOAP (that is, the protocol) and information about where the service is located.
• The port specifies a combination of a network address and a binding, which constitute an endpoint.
• A service groups ports together. A service reveals to a calling program where to access the web service, and through which port. It also describes how the communication messages are defined.

Section 1 includes an import statement and a reference to file po.xsd.
Section 2 describes message requestMessage. The description includes the name of the part, and the name of the element that describes the message structure of that part. Message element PurchaseOrder is fully described in the imported po.xsd document.
Finally, section 3 describes port type execute_ptt, which groups a specific operation (execute) with message requestMessage.

The number and order of messages in the portType definition of a WSDL is important. Because we see only a single message listed in the example above, we know that operation execute is a one-way operation. If we saw a second message like in the example below, we could assume that the operation returned a response upon completion.