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The Open GIS Consortium (OGC) announced the approval and release of Geography Markup Language version 3 (GML 3). GML 3 defines a data encoding in XML that allows geographic data and its attributes to be moved between disparate systems with ease. The new release is modular, meaning that users can select out only the parts necessary for use, which simplifies and minimizes the size of implementations. New additions in GML 3 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.
GML 3 is almost entirely backwards compatible with GML 2 so that developers and users familiar with GML 2 can begin working immediately with GML 3. Like GML 2, GML 3 will play a key role in both spatial data encoding and transport, and in the description of geographic objects for geospatial Web services.
Kurt Buehler, OGC CTO, explains, “GML 3’s modular structure means that those choosing to use GML can literally pick out the schemas or schema components that apply to their work. GML 3.0 also includes a sample packaging tool that creates a tailored schema containing only the required components from the GML core schemas.” Buehler also pointed out that it is OGC’s intention that this very broad specification, with more than 1,000 new tags covering over 400 pages, remains relatively unchanged, save for minor bug fixes over the next year or so. This stability will give potential implementers time to learn about and use GML 3 effectively.
Ron Lake of Galdos Systems, who pioneered GML 1.0 and led the subsequent growth of the specification, makes clear, “the new features are designed specifically to address real world problems.” For example, new in GML 3 is the ability to store topology (the relationships between features), geometric curves and time information. The storage of topology is a key requirement for organizations like the Ordnance Survey Great Britain, which uses GML to store its nationwide data layers. Topology is also required for routing applications popular in location-based services. Those working with highway designs and other transportation-related data require accurate curve definitions. Time information is essential in tracking applications (like monitoring ambulance locations) and exploring the movement and growth of natural disasters such as floods and fires over hours, days or months.
The GML 3 specification was submitted by OGC member organizations CSIRO Australia, Galdos Systems (Canada), interactive instruments (Germany), BAE SYSTEMS Mission Solutions (U.S.), US Census Bureau, POSC (U.S.), MapInfo Corp. (U.S.), Oracle Corp. (U.S.), NTT Data Corp.(Japan), and Laser-Scan Ltd. (UK) and is available for download at http://www.opengis.org/techno/implementation.htm.