The user may define subclasses of this class.
Instances of this class are typical two dimensional images, with the origin of the grid the reference Point for each cell assumed to be the upper left hand (northwest) corner, of the grid and cell respectively. Note though that the coordinate for the upper left hand cell is not necessarily (1,1); if the image is part of a larger image structure - as with a tiling system for example - the coordinate value for the upper left hand cell could take on any value. Band interleaved, band sequential, run length encoded, and quadtree structures for the actual values are accommodated through appropriate use of the inherited attribute contents from the domain StructuredData.
If image data is available which does not meet the restrictions of this class, the class Raster may be used directly. For example, this would be the case if the reference Point of each cell is the centre of the cell and not the northwest corner, or if the or if the geometry of the individual cells does not correspond exactly with the geometry of the grid (e.g. circular cells).