Robin Paulson wrote: >> But why do we need a category at all? Might it not be better to simply >> say "this is a tram stop and these are its properties". >> >> Instead of >> highway=primary, ref=A1303, name=High Street >> we'd say >> primary_road(ref=A1303, name=High Street) >> [note: please don't think I'm proposing a syntax here, I'm just >> illustrating the concept - a concept which is not uncommon] > > categories make it very easy to select a wide group of items based on > their properties. for highways it would be fairly trivial to select > 'primary_road', 'secondary_road'. etc. in a multi-select, but some > categories - shop - will have hundreds of sub-types. > > this enables others to very easily make custom maps, only showing the > data they want, by quickly hiding other information
The main thing to remember is that we need to render elements and the primary keys like 'highway' or 'railway' allow a fast memo for a different line type. While a single 'linetype' reference could be used, see next note ... >> A tram stop is just a tram stop. A bus_guideway is just that, there's no >> need to argue the nuances of whether it is a railway-like feature or a >> highway-like feature - it doesn't then matter. > > no. this is one area where current maps fall down. what we are doing > enables very easy processing of a lot of tags/groups of tags and to > produce complex queries very quickly And further the current map has major holes when one starts looking at route planning. This is an area where the nature of routes is even more critical and the mode of movement will determine which routes can be used and which points indicate a transfer from one form to another. -- Lester Caine - G8HFL ----------------------------- Contact - http://home.lsces.co.uk/lsces/wiki/?page=contact L.S.Caine Electronic Services - http://home.lsces.co.uk MEDW - http://home.lsces.co.uk/ModelEngineersDigitalWorkshop/ Firebird - http://www.firebirdsql.org/index.php _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
