Understanding Web Processing Services

A WPS is an OGC standard to invoke geospatial processing services across the Web. The standard (http://www.opengeospatial.org/standards/wps) defines a structure that allows for a common interpretation of input and output parameters to processing services. The standard provides an abstract layer to individual vendors' internal processing engines and ensures that clients can call any WPS, irrespective of its backend technology. The standard stipulates three operations that must be exposed:

Operation	Purpose
GetCapabilities	This operation returns an XML document that describes the capabilities of the WPS, the processes on offer, and how they can be called.
DescribeProcess	This operation returns an XML document that provides a detailed description of the process and includes the details required to provide the right inputs and to be able to understand the responses.
Execute	This operation is what a client will call when they want to invoke a specific process...