RE: Status of the OpenGIS Geography Markup Language (GML).

["Carl Reed OGC" <creed@opengeospatial.org>]

Dear TC -

 

At last Tuesday's GIS SC conference call, the group asked that I provide an update on the current status of the Geography Markup Language. Below the bullets is a short description of GML extracted from the GML document.

• GML 3.1.1 is the current version of the specification.
• The GML 3.1.1 spec can be found on the OGC web site (as soon as the OGC web guys update the link!) under http://www.opengeospatial.org/specs/
• GML 3.1.1 is also the same as the ISO 19136 GML Draft International Standard. GML should go to ISO International Standard status later this year. At the same time, the OGC will change our version number to 3.2.  GML 3.2 and ISO 19136 will be identical.
• GML is a very rich spec - and long. However, it is designed so that developers can create profiles (restricted subsets) and application schemas (GML plus extra). There are currently dozens of GML profiles and schemas. Some are very simple (see www.georss.org) and some are amazingly rich and broad in their scope (see CityGML at http://www.citygml.org/)
• Other standards organizations have or are beginning to use profiles and application schemas of GML. Examples are the Open Mobile Alliance use of GML in the Mobile Location Platform API and the near term use of a small profile of GML as part of the standards work of IEEE 1451 and by the IETF as part of the PIDF-LO standard.
• Perhaps the most recent really interesting use of a GML profile is for an element of the new Avionics standard being developed in Europe.
• There are beginning to appear tools for more easily developing profiles and application schemas of GML.
• A set of press releases and related information on GML can be found not only on the OGC web site but also at http://xml.coverpages.org/geographyML.html (which is maintained by OASIS!).
• And last but not least,  the OGC members have just submitted a new GML application schema relating to the use of the Geography Markup Language in JP2 (JPEG 2000) image files. The goal is to support a standardized mechanism for inclusion of geo-referencing information as XML-encoded metadata within the ISO 15444 JPEG 2000 image format.

Hope this helps!

 

Carl

 

What is GML? GML "is an XML grammar written in XML Schema for the modeling, transport, and storage of geographic information; it provides a variety of kinds of objects for describing geography including features, coordinate reference systems, geometry, topology, time, units of measure and generalized values. New additions in GML 3.x include support for complex geometries, spatial and temporal reference systems, topology, units of measure, metadata, gridded data, and default styles for feature and coverage visualization. The GML 3.x modular structure means that developers choosing to use GML can literally pick out the schemas or schema components that apply to their work. GML 3.x also includes a sample packaging tool that creates a tailored schema containing only the required components from the GML core schemas. The normative parts of the specification use the W3C XML Schema language to describe the grammar of conformant GML instances. The specification also uses the Recommended XML encoding of Coordinate Reference System definitions prepared by the CRS WG of OGC.

 

 

Carl Reed, PhD
CTO and Executive Director Specification Program
OGC

 

The OGC: Helping the World to Communicate Geographically

 

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