On Thu, May 15, 2014 at 3:01 PM, Colin Smale <colin.sm...@xs4all.nl> wrote: > It is not actually an attribute of the place at all, because if you > moved the place to e.g. the middle of the Atlantic Ocean it would no longer > be a capital. It is an attribute of the relationship between the place and > an (administrative) area. So the place and the area (represented by a > relation in OSM) may reference each other, for example by including the > place in the relation with a role such as admin_centre. Because a place > cannot be a capital in and of itself (it can only be a capital OF somewhere) > putting these tags on the place node is a denormalisation - to make things > more convenient for the data consumers, so they don't have to go through the > relations to see if a place is a capital or not. Such denormalisations are > not always a Bad Thing (it's a balance), but there must be an acceptance > that there is only One Truth, and zero or more derivatives. The One Truth > would be in the relations and we will need a mechanism (or at least an > algorithm) to derive the tagging for the place from the relations which > reference it.
+1 Note: because apps need to support certain kinds of relations (turn restrictions, multipolygon rendering, etc.), it "should be easy" (as far as I can imagine the algorithm) to extend such support (without sacrificing performance) to figure out whether a city is a capital by reading the list of members of the relations the city's node is a member of. > capital=2 only means it's the capital of A country. Without a link to the > country in question, this tag could be misused to increase prominence on the > maps, AKA "mapping (incorrectly) for the renderer", which is "frowned upon". +1 > So I say let's ban capital=* and admin_level=* on the place nodes! I tend to agree, and I don't see yet any practical situation where using those tags is absolutely necessary and reading from a relation is not possible/too difficult. > Colin. > > > > On 2014-05-15 19:36, fly wrote: > > Am 15.05.2014 18:32, schrieb Andreas Goss: > > Am 5/15/14 16:30 , schrieb fly: > > Regarding the original discussion I am in favour of using capital=[2-10]* if > an additional tag is needed. > > I meant additional to the roles for the boundary relation above (cutted). > > admin_centre for 1 or more nodes > capital if not equal to admin_centre or more than one admin_centre present. > > The semicolon (;) is defined as value separator so we could have > capital=4;6;8 or similar. > > This just sounds like a disaster waiting to happen. I also don't see why it > would be needed. You are doubling the risk of errors when it comes to > admin_levels. Now you don't just have to ensure all relations are correct, > but also all nodes. > > As we are talking about admin_level (<-> capital) on nodes and it was > mentioned that it might be easier to use and I am not sure if it is used. > > If any I would go with capital=* and not admin_level=* > > You also have no reference to those numbers. When you add one admin_level to > a relation that relation has a name (Bavaria is a state). When placing > admin_centre you know the name of the relation and of the city so you can > make a connection (Munich is the capital of Bavaria). And while that maybe > is obvious at level 2 and 4, it becomes more compicated when you get into > smaller administrative areas. This also makes it more complicated to find > errors in the first place. I also bet that people are going to assume that > some numbers are missing and are simply going to add them, especially as it > varies from country to country, from state to state etc. Others might simply > add a number with good intend, because they had the wrong admin_levels in > mind. > > Cheers fly > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > -- Fernando Trebien +55 (51) 9962-5409 "Nullius in verba." _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
