WSDL 2.0 - slide "Purpose of a WSD (2/2)"

A WSD is intended for use by a WS and its clients.
The purpose of the WSD is to ensure that the interacting parties agree on the syntax, datatypes and protocols they will use to interact.
A WSD represents a contract between the interacting parties.
The meaning of a Web Service Description (WSD) is determined solely by its logical content — not its origin or creation history.
1. Who wrote the WSD is irrelevant to the meaning and purpose of the WSD.
2. The meaning of the WSD is not dependent on who uses it or how it is used.
3. How the interacting parties reached agreement on the WSD is irrelevant to the meaning and purpose of the WSD.
4. In many cases, the WSD will be provided by the WS on a take-it-or-leave-it basis. In other cases it may be developed collaboratively, by a third party or entirely by a client.
A complete WSD defines an interface that is potentially usable by multiple clients to interact with a particular Web service.
The interface/portType portion of a WSD defines an abstract interface that is potentially usable by multiple clients to interact with multiple Web services.