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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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