Styled Layer Descriptor version 1.1.0 (2010-02-01) SLD is an OGC Standard. Copyright (c) 2007,2010 Open Geospatial Consortium. To obtain additional rights of use, visit http://www.opengeospatial.org/legal/ . A StyledLayerDescriptor is a sequence of styled layers, represented at the first level by NamedLayer and UserLayer elements. SLD LIBRARIES The UseSLDLibrary tag specifies that an external SLD document should be used as a "library" of named layers and styles to augment the set of named layers and styles that are available for use inside of a WMS. In the event of name collisions, the SLD library takes precedence over the ones internal to the WMS. Any number of libraries may be specified in an SLD and each successive library takes precedence over the former ones in the case of name collisions. LAYERS AND STYLES A NamedLayer is a layer of data that has a name advertised by a WMS. A NamedStyle is used to refer to a style that has a name in a WMS. A UserLayer allows a user-defined layer to be built from WFS and WCS data. A RemoteOWS gives a reference to a remote WFS/WCS/other-OWS server. A Service refers to the type of a remote OWS server. LayerFeatureConstraints define what features & feature types are referenced in a layer. A FeatureTypeConstraint identifies a specific feature type and supplies fitlering. LayerCoverageConstraints define what coverage offering subsets are referenced in a layer. A CoverageConstraint identifies a specific coverage offering and supplies time and range selection. The CoverageExtent describes the time or range selections. A RangeAxis describes the range selection for a coverage. An Extent gives feature/coverage/raster/matrix dimension extent. A UserStyle allows user-defined styling and is semantically equivalent to a WMS named style. External FeatureTypeStyles or CoverageStyles can be linked using an OnlineResource-element