On Saturday, 19 April 2008 11:46:52 +1200, Robin Paulson <[EMAIL PROTECTED]> writes: > 2008/4/18 Steve Hill <[EMAIL PROTECTED]>: > > > structure=pole > > > highway=bus_stop > > > amenity=post_box > > > > Ok, but you still have a potential conflict here. Hypothetically, you > > could have a "timetable" tag which applies to both a bus stop (tells you > > when busses arrive) and a post box (when is the post collected?). A neat > > solution is to have "bus_stop:timetable" and "post_box:timetable". > > sorry, i should have made that clearer. i would do this as 3 separate > items, maybe as a relation (slight overkill, but anyway). the relation > would contain 3 nodes, one for the pole, one for the bus stop and one > for the post box. thus each can have it's own timetable without any > confusion. i would never tag one point (or way) as two separate items, > that's asking for trouble, even if the tags don't clash > > technically this is wrong (not all 3 nodes can easily share the same > point and still be editable), but i don't see a huge problem in 2 of > them being slightly offset
They can share the same _position_, represented in OSM as one node. IMHO the only "natural" possibility in OSM to describe three different entities at the same position is by using "relations". I.e., put the node to its physical location, and add three relations with this node as member to describe (a) the pole, (b) the bus stop, and (c) the post box. > > > a lot of the disputes over tagging are caused by people confusing > > > physical items with conceptual ones; if we thought about separating > > > them before debating a tagging scheme, things would be a lot clearer > > > > That may be, but I still think in some cases you are going to want > > multiple > > conceptual items attached to a single item - namespacing allows this to be > > done without risk of conflicting tags and makes it more obvious how the > > tags > > interact with each item (conceptual or physical). > > > > The same thing _could_ be done with relations (i.e. you mark up the > > physical items with ways and nodes and use relations containing physical > > items to represent the conceptial things). But at the moment that would be > > even more complex than a clear set of namespaces. ... if the OSM editors support a basic set of relations to add groups of tags to a single item as easy as adding a single tag to a node/way, IMHO namespaces are not really needed. Best wishes, -bernd _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
