The key GML geometry object types in GML 1. 0 and GML 2. 0, are the following:

GML defines features distinct from geometry objects.

In GML, a feature can have various geometry properties that describe geometric aspects or characteristics of the feature ( e. g. the feature's Point or Extent properties ).

GML also provides the ability for features to share a geometry property with one another by using a remote property reference on the shared geometry property.

An xlink: href attribute on a GML geometry property means that the value of the property is the resource referenced in the link.

For example, a Building feature in a particular GML application schema might have a position given by the primitive GML geometry object type Point.

Coordinates in GML represent the coordinates of geometry objects.

A coordinate reference system ( CRS ) determines the geometry of each geometry element in a GML document.

The following GML example illustrates the distinction between features and geometry objects.

The GML Point Profile contains a single GML geometry, namely a < gml: Point > object type.

GML, on the other hand, offered a limited set of primitives ( geometry, feature ) and a recipe to construct user defined object ( feature ) types.

* GetFeature-this performs the actual query-parameters such as bounding box and any other filters should be passed in, as appropriate, and the WFS service then returns a GML resultset containing full geometry and feature attributes.

Goldfarb hit upon the basic idea while working on a primitive document management system intended for law firms in 1969, and helped invent IBM GML later that same year.

GML serves as a modeling language for geographic systems as well as an open interchange format for geographic transactions on the Internet.

The following profiles, as defined by the GML specification, have been published or proposed for public use:

* A Point Profile for applications with point geometric data but without the need for the full GML grammar

* A GML profile for GMJP2 ( GML in JPEG 2000 )

* A GML profile for RSS

Profiles are often created in support for GML derived languages ( see application schemas ) created in support of particular application domains such as commercial aviation, nautical charting or resource exploitation.

Some other markup languages for geography use schema constructs, but GML builds on the existing XML schema model instead of creating a new schema language.

Whereas GML is a language to encode geographic content for any application, by describing a spectrum of application objects and their properties ( e. g. bridges, roads, buoys, vehicles etc.

KML can be used to carry GML content, and GML can be “ styled ” to KML for the purposes of presentation.

Mr. Ron Lake started work on GML in the fall of 1998, following earlier work on XML encodings for radio broadcasting.

In October 1999, Galdos Systems rewrote the SFXML draft document into a Request for Comment, and changed the name of the language to GML ( Geography Markup Language ).

Even before the passage of the Recommendation Paper at the OGC, Galdos had started work on an XML Schema version of GML, replacing the rdf: resource scheme for remote references with the use of xlink: href, and developing specific patterns ( e. g. Barbarians at the Gate ) for handling extensions for complex structures like feature collections.

Much of the XML Schema design work was done by Mr. Richard Martell of Galdos who served as the document editor and who was mainly responsible for the translation of the basic GML model into an XML Schema.

This laid the foundation for GML 3, although a significant new development occurred in this time frame, namely the intersection of the OGC and ISO TC / 211.

While a basic coding existed for most of the new objects introduced by the GML / G-XML agreement, and for some introduced by Galdos within the OGC process ( notably coverages ), it soon became apparent that few of these encodings were compliant with the abstract specifications developed by the ISO TC / 211, specifications which were increasingly becoming the basis for all OGC specifications.

For example, an SGML interpreter might be programmed to parse GML, wherein the tags are delimited with a left colon and a right full stop, thus, an: e prefix denotes an end tag:.

For example, if a user wants to make a simple 3D game but has no experience with GML, they can download a 3D Library.

( Note that although GML versions 1 and 2 had the < gml: coord > element, it is treated as a defect and is not used.

At this point in time, G-XML was still written using a DTD, while GML had already transitioned to an XML Schema.

SGML, which was based on both GML and GenCode, was developed by Goldfarb in 1974.

The standard generalized markup language ( SGML ) was based upon IBM Generalized Markup Language ( GML ).

The original GML model was based on the World Wide Web Consortium's Resource Description Framework ( RDF ).

These issues, including the use of RDF, were hotly debated within the OGC community during 1999 and 2000, with the result that the final GML Recommendation Paper contained three GML profiles – two based on DTD, and one on RDF – with one of the DTD ’ s using a static schema approach.

This coverage model is concretized to the level of interoperability by the OGC standard GML 3. 2. 1 Application Schema-Coverages ( often referred to as GMLCOV ) which in turn is based on the Geography Markup Language ( GML ) 3. 2, an XML grammar written in XML Schema for the description of application schemas as well as the transport and storage of geographic information.

* Geography Markup Language ( GML )-XML based open standard ( by OpenGIS ) for GIS data exchange

GML's graph model is essentially the same as RDF, on which early versions of GML were based.

In the early 1980s, IBM developed a dedicated publishing tool called Information Structure Identification Language ( ISIL ) based on GML.

GML was a set of macros on top of IBM Script.

Application schemas can be built on specific GML profiles or use the full GML schema set.

The citation on the award reads “ In particular, this award recognizes your great achievement in creating the Geography Markup Language, ( GML ), and your uniquely sensitive and effective work to promote the reconciliation of national differences to promote meaningful standardization of GML on a global level .” Simon Cox ( CSIRO ) and Clemens Portele ( Interactive Instruments ) also subsequently received the Gardels award, in part for their contributions to GML.