Web Map Service

Web Map Service (WMS) is an openly-documented, standardized API (by the Open Geospatial Consortium) for serving map data in response to geographically-specified requests. It defines particular requests and responses done using the HTTP protocol and returning both text data (usually in the form of XML) and graphical maps (which can be PNG, GIF, JPEG, TIFF, or other formats).

Specs

 * WMS 1.1.0 spec
 * WMS 1.1.1 spec
 * WMS 1.3.1 spec

Software

 * MapServer

Links

 * Wikipedia article
 * Open Geospatial Consortium site