The OGC Announces Styled Layer Descriptor & Symbol Encoding Specifications

Sam Bacharach Executive Director, Outreach and Community Adoption Open Geospatial Consortium, Inc tel: +1-703-352-3938 sbacharach [at]
Wednesday, 15 August 2007 UTC

August 15, 2007. Wayland, MA. The members of the Open Geospatial Consortium, Inc. (OGC) have approved the OpenGIS® Styled Layer Descriptor (SLD) Implementation Specification (a profile of the Web Map Service) and the related OpenGIS Symbology Encoding Implementation Specification.

The OpenGIS® Styled Layer Descriptor (SLD) profile of the Web Map Service Implementation Specification defines an encoding that extends the Web Map Service specification to allow user-defined symbolization of feature and coverage data. It allows users to determine which features or layers are rendered with which colors or symbols.

SLD addresses the important need for users (and software) to be able to control the visual portrayal of the geospatial data. The ability to define styling rules requires a styling language that the client and server can both understand. Symbology Encoding provides this language, while the SLD profile of WMS enables application of Symbology Encoding to WMS layers using extensions of WMS operations. Additionally, SLD defines an operation for standardized access to legend symbols.

The OpenGIS Symbology Encoding Implementation Specification defines Symbology Encoding, an XML language for styling information that can be applied to digital Feature and Coverage data.

The OpenGIS® Styled Layer Descriptor (SLD) profile of the Web Map Service is, together with the OpenGIS Symbology Encoding Implementation Specification, the direct follow-up of Styled Layer Descriptor Implementation Specification 1.0.0. The old specification document was split into two documents to allow parts that are not specific to WMS to be reused by other service specifications. Symbology Encoding is independent of any service descriptions and could therefore also be used to describe styling information of systems not connected to any kind of service (e.g. desktop geographic information systems), while the SLD profile of WMS describes how Symbology Encoding can be applied to WMS layers.

The OGC® is an international industry consortium of more than 340 companies, government agencies, research organizations, and universities participating in a consensus process to develop publicly available interface specifications. OpenGIS® Specifications support interoperable solutions that "geo-enable" the Web, wireless and location-based services, and mainstream IT. The specifications empower technology developers to make complex spatial information and services accessible and useful with all kinds of applications. Visit the OGC website at