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.
Version 3.2 introduced a new GML XML namespace and represents ISO standard 19136. Full specifications can be found at http://www.opengeospatial.org/standards/gml