Styled Layer Descriptor (SLD)
Geographic layers hosted by the MassGIS Web Mapping Services can be styled with instructions given in the GetMap request itself. This is called SLD or Styled Layer Descriptor. SLD is an OGC specification. While MassGIS provides a default style for each layer and sometimes other additional styles, not all possibilities can be pre-created. The user may require a new color (due to combining this layer with certain other layers). Or the user might have sensitive data on their server that they cannot share with MassGIS. The user requests a map and can color features (such as towns) based on an attribute (name or id number). The MassGIS web mapping server will dutifully return a map with such-and-such towns colored red, without needing to know why there were chosen. SLD can also substitute other graphic symbols for points, lines and polygon fills. SLD requests can be either URL or XML. SLD requests are longer than requests using MassGIS pre-made named styles, but due to the flexibility in creating maps the possibilities are enormous.
A Note on Colors
In SLD requests you'll see colors referred to using a hash mark: #, plus 6 letters or numbers.
These are hexadecimal colors. For example, #000000 is black, #FFFFFF is white.
The Point Example provides both URL and XML request format.