Interesting, I remember long ago trying to upload (by accident) a set of relations with a cyclic dependency and receiving a server error. Maybe the message was phrased in a misleading way but the error was actually generated by JOSM. Will try again.
Dependency checking must be aware of cycles, otherwise it may end up running an infinite loop. There are some other scenarios, such as retrieving a relation's incomplete members, where a self-reference can be problematic, but that's not the server's responsibility. I can't imagine right now any scenario where self-references or cyclic references woud be necessary to represent any information. (Not suggesting the the server should implement that check.) On Sat, Jun 27, 2015 at 9:03 PM, Paul Norman <[email protected]> wrote: > On 6/27/2015 1:14 PM, Fernando Trebien wrote: >> >> Actually no, the server checks for circular dependencies, and a >> relation pointing to itself is a cycle. Try it, the server returns a >> validation error. > > Nothing in the OSM data model prohibits a relation that references itself, > or relations that form a cycle. > > As an example, see https://www.openstreetmap.org/relation/1368401 which > contains itself twice. Longer cycles are also possible. > > I can't imagine a case where a cycle is sensible, and they are often > difficult to delete, first requiring modifying the relations to remove the > cycle, then deleting the relations. > > > _______________________________________________ > talk mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk -- Fernando Trebien +55 (51) 9962-5409 "Nullius in verba." _______________________________________________ talk mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk
