Re: [udig-devel] Re: Proposals: Topology

[Justin Deoliveira <jdeolive@xxxxxxxxxxxxxxxx>]

The geotools graph module might be a good place to start as a base for a 
Topology API. It really needs more documentation, I have been wanting to 
get to that for some time now. However a topology API is something I 
myself would love to see as well so if it started up I could spend some 
time spiffing up the docs.

That being said I have used it to do network analysis and it has held up 
quite nicley. It is also used in some geoserver validation code to 
validate polygon coverages.

-Justin

Matthias Basler wrote:
> Citing Diatchkov Vitali:
>
> > It is obvious during vector data editing operations it is necessary to
> > preserve topological consistence between different vector objects. Feature
> > model is not appropriate at all because of there is no topological
> > information keeping when each feature is supposed as a standalone feature.
> > The case is when two features with polygonal geometries touch each other on
> > some common segment of boundary and we change boundary points of one of
> > them. Here this operation is hard to trace in respect to the boundary points
> > of second feature. I want to move common segment of both features
> > simultaneously. When we have simple model of features with geometry without
> > topological information it is hard to maintain topological relations.
> >
> > So the proposal is to build Topology Data Model for such operations from a
> > list of simple features with geometry.
>
>
> Yes, please! I'd like to help with this, if I can.
>
> A good topology API is also on my wish list for three reasons
> - topological editing functions as described (no sliver polygons and such)
> - I don't like GeoTool's current geometry API, simply because of the fact that
> it doesn't use interfaces but uses just plain JTS classes.
> - I want 3D geometry and - if possible - 3D topology.
>
> I believe (as does obviously Diatchkov) that it is possible without problems to
> also represent non-topological geometries using a topological API. So there
> should not be the need for two competeting APIs (topological vs. non-top.)
>
> The third point above (3D geometry) is maybe not your concern, but I'd like to
> ensure that any API that is possibly created does at least offer the
> possibility to be easly extended to the third dimension. (And I mean real 3D,
> not just 2.5D with elevation models.)
>
> Jody wrote:
>
> > Having real topology is better, but hard to do.
>
>
> Now, I am (as usual) a bit naive, but with my mathematical understanding I don't
> see any big problem for creation of such API. (Actually I already tried it ...)
> Maybe there are some aspects of it which I don't yet see, which are the "hard"
> ones.
>
> One issue that other GeoTools members might have (but not me), is how a possible
> Topology API could be related to the GeoAPI geometry interfaces. Are they
> topology-aware? Here I need suggestions from the other GeoTools members, how
> these concepts could all fit together in GeoTools.
>
> Anyway, I would suggest that you, Diatchkov, attend the IRC session on next
> monday (see http://geotools.codehaus.org/Communication), so we can discuss this
> topic there.
>
> Matthias Basler
> c9bama@xxxxxxxxxxx
>
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