Geographic MetaData (GMD) extensible markup language is a component of the XML Schema Implementation of Geographic Information Metadata documented in ISO/TS 19139:2007. GMD includes all the definitions of http://www.isotc211.org/2005/gmd namespace. The root document of this namespace is the file gmd.xsd. This extent.xsd schema implements the UML conceptual schema defined in A.3.1 of ISO 19115:2003 and the associated corrigendum. It contains the implementation of the following classes: EX_TemporalExtent, EX_VerticalExtent, EX_BoundingPolygon, EX_Extent, EX_GeographicExtent, EX_GeographicBoundingBox, EX_SpatialTemporalExtent, EX_GeographicDescription. Time period covered by the content of the dataset Vertical domain of dataset Boundary enclosing the dataset expressed as the closed set of (x,y) coordinates of the polygon (last point replicates first point) Information about spatial, vertical, and temporal extent Geographic area of the dataset Geographic area of the entire dataset referenced to WGS 84 Extent with respect to date and time