The Open Geospatial Consortium (OGC®) seeks public comment on the candidate version 3.3 of the OGC Geography Markup Language (GML). GML 3.3 builds on GML 3.2.1, published by ISO as ISO 19136:2007, and extends GML with additional schema components based on requirements requested by various domains of interest. For example, the 3d modeling community suggest the addition of triangular meshes (TINs) to GML. GML 3.3 is fully backwards compatible with GML 3.2.

GML defines an
XML data encoding for geographic data and a grammar to express models of such data using XML Schema. GML has come into wide use since it was first adopted as an OGC standard in 2001 ( http://www.ogcnetwork.net/gmlprofiles for examples). GML is the standard that enables information communities and other standards organizations such as the Internet Engineering Task Force (IETF) and OASIS to insert geospatial elements into their standards and be confident that their standards will be compatible with mainstream information infrastructure methods of conveying spatial/temporal information.

Some of the changes between the previous version 3.2.1 and 3.3 are:

• Support for additional date representations based on ISO 8601 (Representation of dates and times)
• Support for an additional, compact encoding of commonly used geometry types
• Support for a new encoding of Triangulated Irregular Networks (TINs)
• Support for Linear Referencing
• Extensions to the XML encoding rule
• Support for grids used by the meteorological and ocean observation communities

All extensions are made in separate XML namespaces to support a modular use of components from the GML schema.

Information on the change requests addressed in GML v3.3 can be found at http://external.opengeospatial.org/twiki_public/GML/ChangeRequests. The candidate OGC GML v3.3 Standard documents are available for review and comment at http://www.opengeospatial.org/standards/requests/79.