Greetings to the list, I've started revising my bridge tagging proposal <http://wiki.openstreetmap.org/wiki/Proposed_features/Bridge_types> based on the comments received in the last go-round in January. There are three specific questions I'd like some feedback on before I submit a full RFC again.
As preface, I should note that I feel it is important to create at least one key in addition to "bridge". Trying to fit all of the proposed values in one key will inevitably lead to conflicts: how do we represent a beam bridge that is also covered? A viaduct that is also an arch bridge? a cantilever made of truss spans? The "railway" key has problems caused by the all-in-one approach: how do you represent a disused narrow-gauge heritage railway? I'm not going to float a bridge proposal that sets us up for similar problems. That said, the first of my questions is "How should we divide these values among keys"? My proposal basically follows the dichotomy Martin Koppenhoefer laid out here <http://lists.openstreetmap.org/pipermail/tagging/2012-January/009162.html>: one set of tags for "typology" (originally proposed by me under "bridge"), and one set for "structure" (originally proposed by me under "bridge_type"). I'm in favor of placing the "structure" classifications under "bridge:structure" to make it clear what's being classified; there are about 550 occurrences of "bridge_type" at present, most of which can go to "bridge:structure". The bigger question is whether the "typological" values (covered bridges, viaducts, trestle) should stay under "bridge" or move to a "bridge:type" key. The main disadvantage of this move is that there are a large number of existing "bridge=viaduct" instances (about 27,000). The advantage of putting typology under "bridge:type" is that it reduces the number of types a renderer or downstream consumer has to be aware of. All ways tagged with "bridge=yes; bridge:type=..." would be rendered properly as bridges without changes to the current renderers, as would future additions or removals of types. If we consider this, we might also consider whether "movable" should be under "bridge" or "bridge:type". Placing it in the former would mean patching current renderers (e.g., Mapnik), but placing it in the latter makes specific movable bridge types (e.g., bascule, swing) rather wordy to tag, with three separate keys. At present, I tend to favor placing the typology under "bridge:type" except for "bridge=movable" but I would like further opinions and discussion. My second question is whether culverts should be included in this proposal. I included values for culverts in the "structure" classification to maintain compatibility with the Humanitarian Data Model <http://wiki.openstreetmap.org/wiki/Humanitarian_OSM_Tags/Humanitarian_Data_Model>, but tagging culverts on the overhead way (rather than the way that passes through them) is a very small minority tagging style. JaakkoH, who's active in Haiti work, suggested dropping it, and I'm inclined to follow his advice. My third question is what to do about the "drawbridge" value for the proposed "bridge:movable" key. NE2 pointed out that this is something of an attractive nuisance; people tend to use "drawbridge" when they really mean "bascule". Should we drop this value from the proposal because of the potential for misuse? Is there another name that can be applied to those bridges? Your comment on these three points is much appreciated. Once I feel like I have a sense of the community's position, I'll revise the proposal page and put it up for RFC again. Yours, -- Chris Hoess (choess) _______________________________________________ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
