[OSM-dev] Fwd: OSM item tracking

Peter Wendorff wendorff at uni-paderborn.de
Sun Nov 18 13:37:49 GMT 2012

Hi Christian.

Am 18.11.2012 11:41, schrieb Christian Quest:
> I think a better approach is to add a stable ref:* tag to the OSM objects.
I don't understand why that should be a better approach...
> That's the approach we have with most opendata available in France. We 
> add tags like ref:UAI to schools where this ref comes from an official 
> directory of schools. Same with ref:FR:RATP for subway stations and 
> bus_stops in Paris area coming from RATP (Paris public transports).
What if I as a mapper replace the imported school, which has been 
imported as a node by a bunch of buildings, a school yard and so on? 
What should I do with a ref:UAI? probably it would be correct to move it 
to the school yard polygon that encloses the other stuff. But what if 
the id refers to the small shop of the janitor selling sweets and stuff 
to the children? Without a better solution it was more or less correct 
to add that to the school node before, but now it's wrong as it's not 
the area that describes this shop.
To successfully handle that I have to know about ref:UAI or I have to 
ignore it and produce errors with respect to your 3rd party tool or 
database using that reference system.

Novice mappers either ignore these and break stuff, or they leave the 
whole school alone to not break anything - but fail to fix existing bugs 
> It also opens linking possibility to external additional data instead 
> of putting sometime too specialized (and changing) data in OSM itself.
If I delete that ref because it's not documented and I'm not able to 
understand it, this fails.
If you (as the group adding these refs) fail to update them anytime in 
the future (no offense, but often a fact), and the school changes to be 
e.g. a primary school getting a secondary for some reason and getting a 
new ref now, it fails, and nevertheless this then broken data will 
persist in the database as nobody will delete it (due to fear being 
criticised for vandalism).
> It that aspect, a move toward semantic web would be interesting by 
> adding reference to external URI(s) directly on OSM objects.
In that respect and because this has been discussed several times the 
overpass stable ids has been invented to keep the osm objects clean from 
foreign references that nobody is able to check and keep up to date.


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