Andrea Peri 2007 wrote:
I think it would be invalid only in the domain of simple-features.
Not in general.
So I think is right think that for a geometric linestring
selfintersect, or having some consecutive or not consecutive (but
always internal) point repeated is invalid for a simple-feature world,
but it can be valid for the more huge world of "not simple-feature"
geometries.
Another thing to consider - if you change the semantics of isSimple
to report false for linestrings containing duplicate points, then you
have no way of telling the difference between linestrings which
contain true, topological self-intersections and ones which just
happen to contain a topologically irrelevant duplicate point.
Why it is irrilevant ?
See my previous post.
"This is why I say that repeated points are topologically irrelevant -
they are topologically indistinguishable under any continuous
parameterization function."
I think there's some confusion here between the textual and in-memory
representation of a LineString, and its topological, point-set meaning.
In the textual representation repeated points can occur, but in the
topological representation repeated points have no meaning.
--
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022
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