Hi Larry,

I get a case somewhat similar with a parser I wrote for GeoConcept format.
In this format, multi-polygon come as a set of linear rings with no 
special order and eventually some overlaps or other bad topology I 
wanted to catch.
I decided to compute the DE-9IM matrix in a double loop
Something like
List<Polygon> input = ... // the list of polygons issued from my linear 
rings
List<Polygon> result = ... // an empty list of polygons
for (Polygon pi : input)
    for (Polygon pr : result)
        IntersectionMatrix im = pi.relate(pr)
            // then decide if pi is a new polygon, a hole in an existing 
polygon (result), an overlapping polygon...

I must admit this approach may have an unecessary performance penalty 
for a format like shapefile (in my case, correctness was more important 
than performance)

Michaël

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