[postgis-users] PostGIS topology use ?

Andrea Peri aperi2007 at gmail.com
Thu Jul 1 11:00:39 PDT 2010

>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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