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. Note that the concept of feature in GML is a very general one and includes not only conventional "vector" or discrete objects, but also coverages (see also GMLJP2) and sensor data. The ability to integrate all forms of geographic information is key to the utility of GML.

This paper provides a brief introduction to Geography Markup Language (GML). The paper is the first in a series of papers to get you acquainted with this exciting way to represent and manipulate geographic information. Following articles on this site will introduce you to a variety of GML topics including GML map making, GML data transformations, spatial queries and geographic analysis, GML-based spatial databases, and a variety of GML applications including applications to mobile computing systems. We expect GML to revolutionize the treatment of spatial information. GML is web friendly. For the first time spatial information will have a truly public encoding standard.