On Thu, Apr 24, 2008 at 12:51:13PM +0100, Steve Hill wrote: > > piste:lift:occupancy -- wtf? this can only ever happen on a piste:lift > > right? there is absolutely zero point in this tag.. call it occupancy > > -- the result is 100% identical. This is purely namespace wanking for > > the sake of it. It serves no purpose. None. Zip. Nada. The only thing > > this does is make the tag name very long, > > Of course it serves a purpose - it tells you that the value of the tag > describes the occupancy of a lift. An "occupancy" tag could be used to > describe attributes of different types of object - number of people in a > building, number of fish in a pond, etc. Without the name space you need > to get the context from somewhere else (one of the other tags... which > one?) to make it meaningful.
I think that this is the crux of the entire difference in opinions. There appear to be two main points of view: * The tags describe an instance of an object * The usage of the tags on an object should be looked at as a whole * There is no need for namespacing except in cases where (on a single object) the same key can be used multiple times (a la name:en, name:cy, etc.) And the other: * Tags are properties in a global namespace * A given tag should have a single meaning throughout all of the data; if something has a piste:lift:capacity tag, you can tell it is a piste:lift * There is need for namespacing in order to prevent collisions on tags of the same name on different types of objects. I can't claim to have the right answer, but I will state that it is not common in geographic software to have namespaced attributes: in general, when this is the case, it is a namespace based only on the object type which has a specific schema. (In this case, that would be something like pisteLift, since the dataset would be a list of pisteLifts.) That use case can be trivially built up when it's needed based on the other data in the OSM database. I don't really understand why there is a need to have a global definition that a given 'key' has a specific meaning in all contexts, which appears to be the reason for namespacing. It seems to me that creating 'object' definitions that describe objects and their common/useful keys would be most useful from a 'geo' point of view. I can give more examples of what I mean by this if it's neccesary/helpful. Regards, -- Christopher Schmidt MetaCarta _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
