Hi GeoTools community,
as you know i am involved into an implementation of the Feature Geometry
ISO19107. I would like to ask you for your opinion about the semantics of
some geomtric objects and results of operations:
As stated in the Abstract Specification, Primitives and Aggregates DO NOT
contain their boundaries, and Complexes DO contain their boundaries. Set
Operations like union, intersection and difference between those objects
will usually result in a new object, which type (Primitive, Aggregate or
Complex), unfortunately, sometimes is ambiguous.
1)
A simple case: Surface A overlays with CompositeSurface B. Of which type
will A.union(B) be? (In reality, a part of the object contains its boundary
and another part does not).
2)
More complicated case: Surface A overlays CompositeSurface B in a way that
B.difference(A) splits B in two divided regions. As A doesn´t contain it´s
boundary, the two new regions will contain its boundary. Hence, the
resulting object should be a Complex. But Complexes (if i understood the
definition correctly) can not represent divided regions. Only Aggregates (in
that case a MultiSurface) can (but Aggregates do not contain their
boundaries, since its contained Primitives don´t contain their boundaries).
The type of unambigous operation results will be a design decision (like
case 1). Some cases (like 2) bring problems, cause the results might not be
representable correctly.
I would really appreciate any opinion in relation to this topic, especially
about divided regions which contain their boundaries.
Thanks.
Sanjay
--
Sanjay Jena
Brasil:
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Copacabana, Rio de Janeiro
Cel.: +55 21 81995254
Deutschland: Eitorferstr. 5, 50679 Köln
Tel.: +49 221 7885099
Cel.: +49 163 1616196
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