OK, thanks a lot.
I have been misled by the great Validation Plugin in OpenJUMP which has
stayed unchanged since 2004 and which check each LineString component
I'll upgrade that,
> By "GeometryCollection" I meant the concrete class - i.e.
> heterogeneous geometry collections.
> For MultiLineStrings isSimple works the way you describe.
> For MultiPolygons the situation is a bit more complicated. isSimple
> checks for the rings of the polygons being simple. It doesn't check
> for non-crossing polygons, because that's pretty much the definition
> of isValid, and the general approach in JTS is to NOT check for
> validity in operations, to avoid the performance penalty in situations
> where the user knows the geometry is valid. (E,g, the predicates and
> overlay operations work this way as well).
> Hope this clears things up - and always good to have input on the
> sometimes tricky semantics of operations.
> I agree with
> On Sat, Oct 27, 2012 at 7:09 AM, Michaël Michaud
> <michael.michaud@...> wrote:
>> In your blog about isSimple semantic, you wrote :
>> "The code will also be extended to handle GeometryCollections, with the
>> semantics that they are simple if all their components are simple".
>> Seems to me that for MultiLineStrings, it is not completely consistent with
>> - isValid semantic (a simple LinearRing is always the boundary of a
>> valid Polygon, but a simple MultiLineString is not the boundary of a
>> valid MultiPolygon if components have interior intersections)
>> - the way boundaries are defined (if two linestrings of a
>> MultiLineString intersect at their boundary, the intersetion is not part
>> of the MultiLineString boundary)
>> - the isSimple definition for linestring (interior intersections are not
>> I do not pretend to demonstrate anything but have the feeling that
>> a simple MultiLineString should be a PlanarGraph as for simple LineString.
>> Also it sounds strange to me that a simple linear geometry is a valid
>> geometry verifying some more conditions
>> and that an invalid MultiPolygon can be considered as simple (if it
>> contains simple, overlapping polygons)
>> My 2 cents,
>> WINDOWS 8 is here.
>> Millions of people. Your app in 30 days.
>> Visit The Windows 8 Center at Sourceforge for all your go to resources.
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