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Possible relationships between objects are defined by the dimension of intersections between point-sets representing the geometric objects. With this theory seven binary topological relations (touching, overlapping, crossing, containing/inside-of, covering/covered-by, equal, disjoint) can be defined. They are mutually exclusive and cover all possible cases (see  for a proof). These relations are (partially) applicable to regions, text strings, lines, arrows, and end points of arrows (see ). Figure3 illustrates the four relations that are used for PJ.
Figure 3: Spatial relations