[Tagging] Mapping a negative

[Bryce Nesbitt]

On 11/08/2011 09:19 PM, John Smith wrote:
> On 9 November 2011 16:12, Bryce Nesbitt<bryce2 at obviously.com>  wrote:
>> I've run into a curious use of a tag, to map the lack of a thing.
>> At least that's what I think mappers are doing.
>>
>> One might normally expect a well, mountain hut, highway rest area, or toilet
>> to offer drinking water. Some mappers have placed:
>>      drinking_water=no
>> To indicate the normal expectation is wrong.
> All the signs round here have potable yes/no depending if it's safe to
> drink or not.
Though potable=yes/no
     describes a condition of a facility, not the lack of a facility.

I suppose
     amenity=drinking_water
     potable=no
Is a possibility, but then why call it drinking water?  Why not then 
have a more generic water tap which may or may not be potable:
     amenity=water_tap
     potable=yes
     outlet=hose,fountain,faucet
     volume=large (e.g. replaces 
http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dwater_point )



Are there any other OSM conventions that indicate a /lack/ of a 
facility?  Maybe:
     toilets=no
     elevator=no
     parking_garage=no
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20111114/a9443269/attachment.html>