OGC WMS is an interoperable web mapping system. It
provides common interfaces to connect with the client
application and dynamically process geo-referenced data such
as geographic maps and features coded using Geography
Markup Language (GML) documents. The OGC Web Map
Service specification defines a set of functions that clients may
use to interact with WMS providers (servers). Any client
making requests that conform to the specification can interact
with any server that implements the WMS service. In effect,
this creates an interoperable, distributed web mapping systems.
An OGC web map server implements three functions:
GetCapabilities, GetMap, and GetFeatureInfo. The
GetCapabilities function provides the client with a map
server's service metadata, specifying its capabilities.