Web services offer application integrators a loosely-coupled paradigm. In such environments, intermediaries can be very powerful.
Intermediaries are applications that intercept the messages that flow between a service requester and a target Web service, and perform some mediating task (for example logging, high-availability or transformation) before passing on the message. They can be as small as a simple Web service, or as large as the Web services gateway. The Web Services Invocation Framework (WSIF) is designed to make building intermediaries both possible and simple. Using WSIF, intermediaries can add value to the service invocation without needing transport-specific programming.