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A Web Map Service (WMS) is a standard protocol for serving georeferenced map images over the Internet that are generated by a map server using data from a GIS database. The specification was developed and first published by the Open Geospatial Consortium in 1999.
The OpenGIS® Web Map Service Interface Standard (WMS) provides a simple HTTP interface for requesting geo-registered map images from one or more distributed geospatial databases. A WMS request defines the geographic layer(s) and area of interest to be processed. The response to the request is one or more geo-registered map images that can be displayed in a browser application. Theses images are usually returned as JPEG, PNG, etc but they can also be given in vectorial formats as SVG (Scalable Vector Graphics) or WebCGM (Web Computer Graphics Metafile). The WMS standard can perform three basic operations: - To return the metadata of the service
- To return a map according to the options and parameters given by the user
- To return particular information about a point shown in the map
The WMs operations can be invoked using a stándar browser making requests as URLs (Uniform Resource Locators). The result of that request depends on the parameters specified by the user and the operation requested. If the user requests a map, the URL specifies which information has to be displayed, the area that has to be displayed, the coordinates reference system used to limit that area, and the height and width of the image to display. The interface also supports the ability to specify whether the returned images should be transparent so that layers from multiple servers can be combined or not. You can find more information about Web Map Service at http://www.opengeospatial.org/standards/wms
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