>The idea behind topology is the if you have two polygons with a common >edge, the the common edge is only represented as "one edge" and both >polygons share that edge. if you make changes to that edge, then the >polygons both have the same edge so it is not possible to create a gap >between the two polygons.
Ok, I understand your point of view. But I think a gap is always possible to create. Certainly not moving some edges (editing the polygon), but , for example, subtracting a polygon from other two polygon and using a substracting polygon intersect both the polygons. This don't mean that a topology model will denied this subtracting. It allow this subtracting , the subtracting will create a hole between both the polygon (a gap) and the hole will be filled with a special polygon called "universe" that is empty on all the attributes. -- ----------------- Andrea Peri . . . . . . . . . qwerty àèìòù -----------------
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