[Tagging] Everybody is hiding?

Eckhart Wörner ewoerner at kde.org
Fri Aug 10 01:45:17 BST 2012


Hi Ole,

Am Donnerstag, 9. August 2012, 17:55:24 schrieb Ole Nielsen / osm:
> First of all I actually approved the proposal but later realized that
> having variable keys is less than ideal.

then *please* tell me the reason why you believe this is the case, because I haven't seen any compelling counter-argument so far. What I have seen from different people:
- allows for an almost infinite number of keys: existing tagging shows that keys tend to cluster, e.g. maxspeed:(22:00-06:00) is in use 395 (!) times with 6 different values (putting this into perspective: meagre 4494 occurences of maxspeed:backward). Those clustering effects become even stronger with increased usage.
- kills PostgreSQL database performance: when you preprocess your routing data, you have to do a linear scan over all tag hstores anyway.
- difficult because of special chars: the only situation where this actually matters is when you search inside your editor – and in that case the ':' already requires you to quote your key, at least in JOSM
- difficult to parse for computers: every programmer can tell you in a second that this is plain wrong
- difficult to parse for humans: so far, everybody I talked to about this was able to grasp the meaning of maxspeed:(22:00-06:00) = 100 in a split second
And – of course – my favourite:
- un-OSM-y, don't like it

Eckhart



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