Steve Bennett wrote: > For example, around my city there are little "reserves" - patches of > grass reserved by the government for future development such as > freeways or train lines. They often get tagged "leisure=park", but > say I want to start tagging them "landuse=reserve" instead. Suddenly, > instead of being green on mapnik, it will be white again - unrecognised > tag. > > Solution: tag it like this: > landuse=reserve > fallback:leisure=park
No. This is way beyond wrong in several ways. Core principle: you should map what's on the ground. If it's a reserve, call it a reserve. It's not a park, so don't call it a park. The OSM database exists _only_ to record reality. Secondly: as far as I can tell, you're proposing inserting "fallback:leisure=park" into the database at every occurrence of "landuse=reserve". You might also have, I dunno, "fallback:highway=bridleway" for every occurrence of "highway=byway". And so on across loads of tags. This is just redundancy on a massive, massive scale. You're inserting the same "hint" millions of times when you should be inserting it once. If landuse=park always approximates to leisure=park, then that either needs to be in the renderer stylesheets themselves (and it'd be one line in the Mapnik stylesheet or osm2pgsql setup), or in a general equivalence document that all the renderers can use (Shalabh's tree thingy). Rendering information, of any stripe, does not go in the database. That is absolute. You want instant gratification - that's fair enough. But the authors of the stylesheets don't have the time to pander to every possible tag combination - which is also fair enough, they're volunteers too and they have to prioritise. And I hate to say it, but trac shows that people _do_ sometimes invent obscure tags, which is ok, and demand support for them incessantly, which isn't. So the right way to solve it is to lower the barrier to getting Your Favourite Feature rendered. Fortunately this is happening. Cartagen is an instant-gratification JavaScript renderer. It's awesome. Halcyon is the Flash one I'm working on and if you'll permit the immodesty, I'd say it's ok, too. Kosmos is Igor Brejc's long-standing project which gets better by the month and can produce lovely results. Tiledrawer is Mike Migurski's superb "Mapnik for the rest of us" installation which is still a bit more involved, but worth it as the best way to harness Mapnik MONSTER POWER without a nervous breakdown. Cloudmade's Style Editor has some limitations but you can't beat it in UI terms and I'm sure it'll get more flexible in the future, so one to watch. Of course, Osmarender has been around since about 38BC and is reasonably accessible. And there are others. This leads to a virtuous circle: one renderer supports the tag -> tag more widely used -> more renderer support -> and so on. Andy first started rendering ncn_ref on OpenCycleMap several years ago, when OCM was just a little local project rather than the world-conquering behemoth it is today. Now there are cycle renderers for local areas, for Garmins, for routing, and so on. It really works. cheers Richard -- View this message in context: http://old.nabble.com/Suggestion%3A-fallback-tag-tp26827544p26830932.html Sent from the OpenStreetMap - General mailing list archive at Nabble.com. _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
