Chapter 1. Introducing WSDL Contracts

A WSDL document is, at its simplest, a collection of elements contained within a root definition element. These elements describe a service and how an endpoint implementing that service is accessed.

A WSDL document has two distinct parts:

The logical part of a WSDL document contains the types, the message, and the portType elements. It describes the service’s interface and the messages exchanged by the service. Within the types element, XML Schema is used to define the structure of the data that makes up the messages. A number of message elements are used to define the structure of the messages used by the service. The portType element contains one or more operation elements that define the messages sent by the operations exposed by the service.

The concrete part of a WSDL document contains the binding and the service elements. It describes how an endpoint that implements the service connects to the outside world. The binding elements describe how the data units described by the message elements are mapped into a concrete, on-the-wire data format, such as SOAP. The service elements contain one or more port elements which define the endpoints implementing the service.