GeoServer's renderer uses, and is basically built around, the SLD (Styled Layer Descriptor) specification. SLD is an XML (Extensible Markup Language) extension specified by OGC. It allows rich representation of the underlying spatial data regardless of their type. As SLD is XML based, it is a structured text using tags, attributes, and values. In order to understand SLD better, let's go through the description of the style we opened before.
The original SLD specification is very universal and extensive, therefore it is complex. Moreover, GeoServer has a great implementation capable of harnessing most of its features. Therefore, in order to keep the learning curve calm, we will only use a small subset of SLD. We have to make two assumptions in order to do this--we only use catalog styles (that is, static styles managed from GeoServer), and every vector...
