STYLED LAYER DESCRIPTOR version 0.7.2 (2002-09-21) A StyledLayerDescriptor is a sequence of styled layers, represented at the first level by NamedLayer and UserLayer elements. 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. An OnlineResource is typically used to refer to an HTTP URL. LayerFeatureConstraints define what features & feature types are referenced in a layer. A FeatureTypeConstraint identifies a specific feature type and supplies fitlering. An Extent gives feature/coverage/raster/matrix dimension extent. A UserStyle allows user-defined styling and is semantically equivalent to a WMS named style. FEATURE-TYPE STYLING A FeatureTypeStyle contains styling information specific to one feature type. This is the SLD level that separates the 'layer' handling from the 'feature' handling. A Rule is used to attach property/scale conditions to and group the individual symbolizers used for rendering. SYMBOLIZERS A "SymbolizerType" is an abstract type for encoding the graphical properties used to portray geographic information. Concrete symbol types are derived from this base type. LINE SYMBOLIZER A LineSymbolizer is used to render a "stroke" along a linear geometry. A Geometry gives reference to a (the) geometry property of a feature to be used for rendering. A "Stroke" specifies the appearance of a linear geometry. It is defined in parallel with SVG strokes. The following CssParameters may be used: "stroke" (color), "stroke-opacity", "stroke-width", "stroke-linejoin", "stroke-linecap", "stroke-dasharray", and "stroke-dashoffset". A "CssParameter" refers to an SVG/CSS graphical-formatting parameter. The parameter is identified using the "name" attribute and the content of the element gives the SVG/CSS-coded value. The "ParameterValueType" uses WFS-Filter expressions to give values for SLD graphic parameters. A "mixed" element-content model is used with textual substitution for values. A "GraphicFill" defines repeated-graphic filling (stippling) pattern for an area geometry. A "GraphicStroke" defines a repated-linear graphic pattern to be used for stroking a line. POLYGON SYMBOLIZER A "PolygonSymbolizer" specifies the rendering of a polygon or area geometry, including its interior fill and border stroke. A "Fill" specifies the pattern for filling an area geometry. The allowed CssParameters are: "fill" (color) and "fill-opacity". POINT SYMBOLIZER A "PointSymbolizer" specifies the rendering of a "graphic symbol" at a point. A "Graphic" specifies or refers to a "graphic symbol" with inherent shape, size, and coloring. An "ExternalGraphic" gives a reference to an external raster or vector graphical object. A "Mark" specifies a geometric shape and applies coloring to it. TEXT SYMBOLIZER A "TextSymbolizer" is used to render text labels according to various graphical parameters. A "Label" specifies the textual content to be rendered. A "Font" element specifies the text font to use. The allowed CssParameters are: "font-family", "font-style", "font-weight", and "font-size". The "LabelPlacement" specifies where and how a text label should be rendered relative to a geometry. The present mechanism is poorly aligned with CSS/SVG. A "PointPlacement" specifies how a text label should be rendered relative to a geometric point. An "AnchorPoint" identifies the location inside of a text label to use an an 'anchor' for positioning it relative to a point geometry. A "Displacement" gives X and Y offset displacements to use for rendering a text label near a point. A "LinePlacement" specifies how a text label should be rendered relative to a linear geometry. A "PerpendicularOffset" gives the perpendicular distance away from a line to draw a label. A "Halo" fills an extended area outside the glyphs of a rendered text label to make the label easier to read over a background. RASTER SYMBOLIZER A "RasterSymbolizer" is used to specify the rendering of raster/ matrix-coverage data (e.g., satellite images, DEMs). "ChannelSelection" specifies the false-color channel selection for a multi-spectral raster source. "OverlapBehavior" tells a system how to behave when multiple raster images in a layer overlap each other, for example with satellite-image scenes. A "ColorMap" defines either the colors of a pallet-type raster source or the mapping of numeric pixel values to colors. "ContrastEnhancement" defines the 'stretching' of contrast for a channel of a false-color image or for a whole grey/color image. Contrast enhancement is used to make ground features in images more visible. "ShadedRelief" specifies the application of relief shading (or "hill shading") to a DEM raster to give it somewhat of a three-dimensional effect and to make elevation changes more visible. "ImageOutline" specifies how individual source rasters in a multi-raster set (such as a set of satellite-image scenes) should be outlined to make the individual-image locations visible.