[OSM-dev] Ways without nodes

[andrzej zaborowski]

[Resending the message because I noticed my oversize attachment
prevented it from getting through, sorry if you get it twice now]

2009/8/25 Stephan Knauss <osm at stephans-server.de>:
> andrzej zaborowski wrote:
>> I can mass delete the empty relations (which are not members of other
>> relations) like you did with ways but I will not go and check each one
>> of the 7k.  Would someone object to me deleting them?  What are other
>> ideas about the origin of empty relations?
>
> Can you post some typical examples? I did a search and found far less empty
> relations than you did:
>
> select id, tags from planet_osm_rels where # parts = 0 GROUP BY tags, id
> 2939 rows retrieved.

Yes, 7000 turns out to have been exaggerated when I looked again.
There were 7000+ objects that were found in a planet snapshot of two
weeks ago and for which my program could not find the bbox.  This
includes relations with no members, the ways with no member (already
gone), relations with only a relation as a member (whose members are
also relations etc etc).  Apparently there are also many ways with
only 1 node.

There are only 4120 empty relations in my snapshot (see
http://openstreetmap.pl/balrog/emptyrels.html).
Examples:

 * some have had members and members were dropped in successive versions:
http://www.openstreetmap.org/browse/relation/47085/history

 * some had no members:
http://www.openstreetmap.org/browse/relation/32141/history

 * some had members which were dropped, _but_ have a "please don't
delete me" tag, I'm not sure what to do with those since this tag is
there since version 1 and may not apply anymore:
http://www.openstreetmap.org/browse/relation/168033/history

color = #FF0000
name = Tour Bike della Transumanza
network = mtb
note = PLEASE DON'T REMOVE - WILL BE USED FOR CYCLEMAP RENDERING
operator = Vallelongabike.net
rcn = yes
rcn_ref = 01
ref = 01
route = bicycle
type = route

There are 1279 address relations for each street in Minsk from a
osm-belarus import, whose only member is the city Minsk (role is_in)
and are not referenced otherwise (all successive id's between 80569
and 81927.

>
> It's easy with JOSM. Create a relation and upload. Not even a warning.

Yes, probably some counter measure should be added.

> About mass delete: I'm not sure about this on relations. Some of them are
> just a few hours old. Maybe the older ones not being referenced by anything.
> Reason would be no one could work with them without knowing their ID. The
> editors can not retrieve them.

Sounds like a good way forward, excepting also the relations with
"don't delete me" tags.

Cheers