On 19 October 2012 10:05, thomas van der veen <[email protected]> wrote: > I have used the terraced house plug in a few times and have found it very > useful, but I don't quite understand the difference between addr:street > (which is what I do at the moment) and adding a relation? > > Could you please explain this a bit more (and if possible in other contexts > then the postcode finder)
Sure. All this addressing is based on the Karlsruhe Schema [1] which was devised as a way of tagging streets by some Germans who wanted to try out tagging a whole city. The original schema was a series of tags you put on each house such as house number, post code etc. The way they originally specified which street a house is on was by the addr:street tag where they would put the name of the street in that tag on each house. During the process of this schema evolving and being used, some people felt that this was redundant and so decided to start using relations to group these houses together (along with the street). I have a feeling this was in the early days of relations when many people weren't sure how to use them and so adoption of this method was slow. So, for adding in data as a mapper, it a difference between adding an 'addr:street' tag to every house in the street or selecting all the houses and roads in the street and adding them to a single relation (with the correct roles). For many people, creating a relation like this is seen as unnecessarily burdensome when for them, the addr:street method describes what they mean just fine. For data consumers (Nominatim, postcode finder, routers etc.) I would argue that it's conceptually simpler to use the relation method since it's explicit about that's in the street and what's not. With the addr:street method, the programmer has to, upon finding a node with an addr:street tag on it, search 'nearby' in the database. This means that they must have a georeferenced database set up and these querys are not as fast as simply node/way lookups. Also, to assemble a full street (from many ways and houses) would require an iterative building process. For me as a data consumer, the advantage of the associatedStreet relation comes from explicitness and speed. What I think we need (and what I've started to look at) is a plugin for JOSM (or built-in for Potlatch) which allows you to simply select the houses and the street, press a button and the relation is magically created. If some of the selected items are already in a relation then the rest of the items are added to it. Some of this is just my (biased) opinion so feel free to do whatever works best for you (of course, you could always do both). For information on exactly how I tag addresses with relations, see [2] (which I'd like to announce is up and running again). Cheers, Matt [1] https://wiki.openstreetmap.org/wiki/Proposed_features/House_numbers/Karlsruhe_Schema [2] http://milliams.dev.openstreetmap.org/postcodefinder/tagging/ _______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
