[OSM-talk] [OSM-dev] Polygons in OSM don't necessarily comply to simple feature specification

[Christopher Schmidt]

On Wed, Apr 16, 2008 at 11:58:21PM +0200, Martijn van Exel wrote:
> Op 16 apr 2008, om 23:41 heeft Christopher Schmidt het volgende  
> geschreven:
> >On Wed, Apr 16, 2008 at 11:28:32PM +0200, Martijn van Exel wrote:
> >It seems likely that the netherlands 'self intersecting polygons' are
> >simply the result of poorly curated coastline imports or something
> >similar: in general, self-intersecting polygons aren't useful for
> >anything I can think of in OSM, but preventing it is hard, and not
> >really within the spirit of *most* simple geographic data tools.
> 
> Why not? Simple Features to me seem to be all about the spirit of  
> simplicity - and they exclude self-intersection.

But implementatons don't. (MS's spatial offering is somewhat lonely in
respecting this.) 

In any case, OSM doesn't have polygons, so OSM can't prevent the
intersection of Polygons. The fact that the interpretation of specific
types of ways as polygons is common does not make the API have that
property. Discourating this behavior, or preventing it, is therefore not
an API level decision, but an editor-level decision.

Regards,
-- 
Christopher Schmidt
MetaCarta