Before revision: In August 2007 the SLD specification was split up into two new OGC specifications OGC press release about symbology encoding and SLD: symbology encoding implementation specification (SE) styled layer descriptor Styled layer descriptor specification now only contains the protocol for communicating with a WMS about how to style a layer.
After revision: In August 2007 the SLD specification was split up into two new OGC implementation specificationsThe OGC Announces Styled Layer Descriptor (SE) Styled Layer Descriptor (SLD) Styled Layer DescriptorSymbol Encoding Specifications: Symbology Encoding specification now only contains the protocol for communicating with a WMS about how to style a layer.