[OSM-talk] conditions as part of value/key

[Tobias Knerr]

Roy Wallace wrote:
> You don't need "all maxspeeds" to be in a single value. Nor would it
> break existing applications. Maxspeed=* is still maxspeed=*. You would
> be adding additional keys such as maxspeed:time, or maxspeed:vehicle,
> or maxspeed:weather, etc. 

That seems to be superior to other value-based approaches I've seen so
far. However, I can't see how you would handle a situation with multiple
conditions for a tag's value, for example what I would express as
"maxspeed[hgv][wet]". Did I miss something or is that simply not possible?

> The only disadvantage is that if you have
> two of the same kind of restrictions, e.g. an "in general" maxspeed,
> plus TWO OR MORE maxspeed:time restrictions, for example, you need to
> add _1, _2 at the end of the keys, which sucks, although John pointed
> out this is apparently already in use.

I haven't ever seen this one being used (though I can imagine it as an
attempt to set multiple alternative names and the like) and for sure I
haven't seen any documentation for it. It definitely isn't really
"key-ish", either. ;)

> But, I disagree with you that putting conditions in keys has much
> advantage over putting conditions in values, so IMHO why not go with
> the gut feeling and keep keys key-ish...

Well, we already have some keys which are actually conditional tagging
in disguise, such as bicycle=yes (which is an access=yes with a vehicle
condition, imo). So /keeping/ keys key-ish might not quite work...

Btw, it's nice to finally get some ideas about the conditional tagging
issue. I only wonder why people didn't provide this sort of feedback
when I explicitly requested it for for my proposal[1] and its
predecessor. *scratches head*

Tobias Knerr


[1]
http://wiki.openstreetmap.org/wiki/Proposed_features/Extended_conditions_for_access_tags