[Tagging] Mapping a negative

[John Smith]

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.