http://opengeospatial.org/standards/
http://opengeospatial.org/standards/wms
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 (returned as JPEG, PNG, etc) that can be displayed in a browser application. 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.
http://opengeospatial.org/standards/wcs
The OpenGIS® Web Coverage Service Interface Standard (WCS) defines a standard interface and operations that enables interoperable access to geospatial “coverages” [http://www.opengeospatial.org/ogc/glossary/c]. The term “grid coverages” typically refers to content such as satellite images, digital aerial photos, digital elevation data, and other phenomena represented by values at each measurement point.
http://opengeospatial.org/standards/wfs
The OpenGIS Web Feature Service Interface Standard (WFS) defines an interface[http://www.opengeospatial.org/ogc/glossary/i] for specifying requests for retrieving geographic features [http://www.opengeospatial.org/ogc/glossary/g] across the Web using platform-independent calls. The WFS standard defines interfaces and operations for data access and manipulation on a set of geographic features, including:
The specified feature encoding for input and output is the Geography Markup Language (GML) [http://www.opengeospatial.org/standards/gml] although other encodings may be used.
http://opengeospatial.org/standards/wps
The OpenGIS® Web Processing Service (WPS) Interface Standard provides rules for standardizing how inputs and outputs (requests and responses) for geospatial processing services, such as polygon overlay. The standard also defines how a client can request the execution of a process, and how the output from the process is handled. It defines an interface that facilitates the publishing of geospatial processes and clients’ discovery of and binding to those processes. The data required by the WPS can be delivered across a network or they can be available at the server.