Organizing Principle: Alternate Hierarchy
Consider two geometric representations of the same data set, such as
- an elevation grid and polygons derived from that grid, or
- two polygonal representations where one set of polygons have been clipped along grid boundary lines but the other hasn't.
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To unambiguously indicate that two or more geometric organizations represent the same underlying data, they can be organized as separate branches of an <Alternate Hierarchy Related Geometry>. The <Hierarchy Data> associated with each branch indicates the reason for that particular alternate representation.