Members of the class SpatialDataSet each contain a series of geographic objects and annotation objects (see below). All such objects are considered to belong to the same data set, generally because of similarities in metadata or referencing. For example, typically the same spatial referencing would pertain to all geographic objects and annotation in a spatial data set. A user could define a subclass of SpatialDataSet called ForestInfo, consisting of a coverage of forest stands, another of streams, and a third of satellite imagery.
SpatialDataSet is a subclass of GeographicObject; consequently, a given spatial data set may contain other spatial data sets. In addition to the class ForestInfo, the classes SoilInfo and WildlifeInfo could be defined as spatial data sets. A NaturalResource class could be specified; objects belonging to this class contain an object from ForestInfo, an object from SoilInfo, and an object from WildlifeInfo.
Through inheritance, an object belonging to any subclass of SpatialDataSet may include an object from the class GeographicObject. This means that the natural resource object above can include a spatial object defining the area of interest. Because a spatial object incorporates both geometry and spatial referencing, the spatial referencing for the area of interest may differ from the various objects contained in the data set. For example, in some jurisdictions a series of mapsheets are based on latitude and longitude values, even though the data described on each sheet is specified using the Universal Transverse Mercator projection.
Where there is interest in establishing catalogues or repositories, spatial data sets are of particular interest as the primary objects to be described.