The user may define subclasses of this class.
Raster is a special type of coverage for which (i) the geometry is restricted to some type of Grid and (ii) the values pertaining to each position in the specified grid are provided by StructuredData. An instance of Grid defines the cellular structure in n-dimensional space (or space/time). An instance of StructuredData contains the integer, real, character string, bit string or octet string values - or a mix of values of these types - as well as the names of the attributes represented by these values.
The subclasses which follow are intended to address common raster structures. Other raster structures may be handled directly by Raster or by user-defined subclasses of Raster. For example, a given application may call for a triangular or hexagonal grid, or a series of specific locations in a grid. Such situations can readily be handled with the appropriate choice of a subclass of Grid as the domain for geometry.