An object belonging to the class GeographicObject represents some part of the real world. It has an actual or potential position in space and time, which is represented by a member of SpatialObject or SpatiotemporalObject. Users can subclass directly from GeographicObject or from its standard subclasses, described below. Four general cases of geographic objects are recognized.
In the first case, the geographic object corresponds to a discrete feature or phenomenon in the real world. Typically users defines subclasses of GeographicObject of particular interest to them. For example, MountainPeak may be specified as a subclass of GeographicObject. An object belonging to this class has a position probably represented through a spatial object as a point on the earth's surface. Another subclass of GeographicObject may be Road. Objects of type Road probably have positions manifested as lines or perhaps long, thin rectangles. Roads, mountain peaks, fleets of trucks, forest stands and the like are geographic objects corresponding to concrete, real world phenomena. However, a geographic object may correspond to an artificial phenomenon, as with a political jurisdiction or school district.
The second general case of geographic objects refers to coverages, that is, descriptions of regions of space which may not necessarily correspond to distinct features. Coverages are described below. The third general case pertains to spatial data sets, collections of spatially referenced data which are grouped together for reasons of convenience, as described later as well. The fourth case concerns graphs, including networks; graphs consist of a series of geographic objects which are connected to other geographic objects. They are also described below.