Geography Markup Language
used to describe geographical features
The Geography Markup Language (GML) is the XML grammar defined by the Open Geospatial Consortium (OGC) to express geographical features. GML serves as a modeling language for geographic systems as well as an open interchange format for geographic transactions on the Internet. Key to GML's utility is its ability to integrate all forms of geographic information, including not only conventional "vector" or discrete objects, but also coverages (see also GMLJP2) and sensor data.
GML model
GML contains a rich set of primitives which are used to build application specific schemas or application languages. These primitives include:
Feature
Geometry
Coordinate reference system
Topology
Time
Dynamic feature
Coverage (including geographic images)
Unit of measure
Directions
Observations
Map presentation styling rules
The original GML model was based on the World Wide Web Consortium's Resource Description Framework (RDF). Subsequently, the OGC introduced XML schemas into GML's structure to help connect the various existing geographic databases, whose relational structure XML schemas more easily defined. The resulting XML-schema-based GML retains many features of RDF, including the idea of child elements as properties of the parent object (RDFS) and the use of remote property references.
Profile
GML profiles are logical restrictions to GML, and may be expressed by a document, an XML schema or both. These profiles are intended to simplify adoption of GML, to facilitate rapid adoption of the standard. 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 Simple Features profile supporting vector feature requests and transactions, e.g.
The public source identifies “Geography Markup Language” as used to describe geographical features. This brief keeps that definition visible, then builds a research path around Geography, Markup and Language.
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This entry incorporates text from “Geography Markup Language” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.