I've been noticing recently how things seem to be heading. Before I was involved with the project there were nodes, segments and ways. Whether there were also relations at that time I don't know. Perhaps the same key could be used more than once on a way - again I don't know.
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. 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. I don't believe the renderers handle all such relations at present (I know they don't handle the interchange relation to display the junction_ref, as it was when I was going to tag nodes as highway=motorway_junction that I discovered the relations), but it does seem that relations are becoming more and more important for many things that we map. Whether in the above case you'd have the dotted line for bridleway and the dotted line for parish boundary rendered on top of the road or not I don't know. I suspect that would be the most accurate rendering. 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. Just some idle thoughts. Ed _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
