The data required by the WPS can be delivered across a network or they can be available at the server.
WPS can describe any calculation (i.e. process) including all of its inputs and outputs, and trigger its execution as a web service.
WPS makes it possible to publish, find, and bind to processes in a standardized and thus interoperable fashion.
More often, it is invoked by a client application that provides the user with interactive controls.
Version 0.4.0 was released as an OGC Request for Public Comment in 2005 and implemented by several early adopters.