JOIN DEPENDENCIES IN RELATIONAL DATABASES AND THE GEOMETRY OF SPATIAL GRIDS

Abstract

It is shown that a relation whose tuples describe a regular folded spatial grid contains a join dependency, that originates in the geometrical properties of the grid. There is a class of join dependencies corresponding to 2-dimensional grids, or polygonal join dependencies, and a class corresponding to 3-dimensional grids, or polyhedral join dependencies, and so on. The simplest known join dependency turns out to be a triangular join dependency. A grid must be folded to determine the tuples of the relation describing it. A regular grid contains only one type of polygon or polyhedron.