On 03/04/2009 14:05, Ed Loach wrote: > Currently we seem to have nodes, ways and relations. A way or node > can be part of any number of relations (I believe), and there are > people using relations for more and more things. Group all the ways > that make a given road into a road relation; all the ways that make > a junction into an interchange relation (or so I've noticed on the > A14 near Bury St Edmunds this morning); and more.
Relations were specifically introduced to allow for groupings, and especially those which *utilise* other ways and nodes or things which aren't physical - for example a bus route or NCN route runs along multiple ways of different types. We could use them to link the way running under a bridge with the bridge passing over, and so on. > In some ways this would allow you to add more than one tag on the > same way with the same key. I could have a relation which represents > a bridleway, which for part of its length happens to run along a > lane (highway=unclassified, perhaps with it's own road relation) > that itself is the boundary between two parishes (boundary > relation). In this case the way is really nothing more than a line > and the relations dictate the three separate uses. Hmm. Notwithstanding the other discussion about bridleways, a bridleway is a kind of road or path and has a physical presence, so that's not really what a relation was intended for. A "horse route" would be and might utilise a road here, a path there and a bridleway somewhere else along it. > I think relations are going to have to be given some serious > consideration as they evolve. If a way is in a relation do the tags > on the way or the relation take precedence - say in a road relation > do you put the access restrictions that apply to the road in the > relation, but if there is a short way in the middle of the road with > different restrictions do we tag that way and hence give the way > tags precedence. Or if a road relation has the ref for the whole > road but another exists on a way, and it differs, do we assume that > the way tag takes precedence, or a mistake. Grouping streets that share a ref seems like a good use for a relation, though I think it would be a shame if this became the standard way of doing it as it is a rather more complicated way of doing it. But in some cases, roads do have more than one ref (European + national, NCN + B Road, or even just two roads come together A11 + A14 north of newmarket, though I think strictly speaking the A14 is the road number and the A11 breaks in two here). So always a mistake is probably too strong, but I'd imagine it generally would be a mistake. We'd have to look at each problem case on its merits I'd have thought. David _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
