[GRASS-user] topology model resume (and some proposals)

[G. Allegri]

I resume (first as a repeat to myself) what I've learned from the various
email on the topic

Vectors can be:

LEVEL 1:
 - no topology -> very limited use
LEVEL 2:
 - unclean topology -> limited use
 - clean topology -> full support

I previously thought that LEVEL 2 was only possible for clean topologies,
and I was wrong...

At the moment there isn't a tool to list the the uncorrect geometries from
a topological point of view. v.build only checks some constraints, not all.
The proposal is to extend it to check against all the rules that are
required to consider a geometry topologically correct (an extended flag to
v defaul.build maybe).

v.in.ogr builds and cleans (by default). It would be useful to have the
"clean" phase available to be launched independently. I mean, something
like an "automatic" flag for v.clean, that would operate the same cleaning
as during the import of a vector.

Conclusions: the topological correctness isn't a constraint for the vector
topology data structure. GRASS haven't all the topology rules hard-coded
(... or yes?). Most of thems (all?) are defined inside the code of v.build
and v.clean, but I suppose that there isn't an autonomous
library/functionality that provide the semantics of a "correct topology".
Am I wrong?

Thanks everyone for the support ;)
giovanni
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