[OSM-dev] Recursive relations

[Maarten Deen]

Karl Guggisberg wrote:
>> This is probably something that the OSM editors should warn users about
>> when they try to create such a relation.
> JOSM doesn't allow to create recursive relations, but it accepts them when
> they are present in the data.

JOSM has in the past accepted recursive relations and it is very likely that 
people still have versions running that do so.

Maarten


> -----Ursprüngliche Nachricht-----
> Von: dev-bounces at openstreetmap.org [mailto:dev-bounces at openstreetmap.org] Im
> Auftrag von Andrew M. Bishop
> Gesendet: Sonntag, 13. September 2009 11:56
> An: dev at openstreetmap.org
> Betreff: [OSM-dev] Recursive relations
> 
> In OSM a relation can contain other relations but it seems that there is
> nothing to check that a relation doesn't contain itself.  I can't think of
> any legitimate reason that it should be allowed though.
> 
> For example relation 15852 has contained itself since version 108 which was
> created at the beginning of July (changeset 1754423).
> 
> Within the UK alone the following route relations all contain
> themselves:
> 
> 12179
> 15852
> 80545
> 101440
> 163368
> 165638
> 165638
> 167468
> 168189
> 170290
> 170290
> 
> Also within the UK there is one boundary relation that contains
> itself:
> 
> 57535
> 
> 
> Obviously it is possible to ignore these when parsing the data (which is
> what I do and what alerted me to them in the first place) but it would be
> better if it didn't happen.
> 
> 
> This is probably something that the OSM editors should warn users about when
> they try to create such a relation.
> 
> Is there somebody that can find and fix all such relations on the server (if
> they have no legitimate use)?
> 
> Obviously self-recursion is easy to find; there might be mutually recursive
> relations as well but I haven't looked for them.
> 
> --
> Andrew.
> ----------------------------------------------------------------------
> Andrew M. Bishop                             amb at gedanken.demon.co.uk
> 
> UK OpenStreetMap Route Relations:
>         http://www.gedanken.org.uk/mapping/osm-routes/route.html
> 
> UK OpenStreetMap Boundary Relations:
>         http://www.gedanken.org.uk/mapping/osm-boundaries/boundary.html