[Tagging] Is tagging of fuel: assumed to be exhaustive?

[Matija Nalis]

On Tue, 18 Apr 2023 17:08:39 +0200, Marc_marc <marc_marc at mailo.com> wrote:
> Le 18.04.23 à 16:53, Mateusz Konieczny via Tagging a écrit :
>> Is tagging of fuel: assumed to be exhaustive?
>
> no, some contributors will fill in what they are interested in,
> others will fill in everything that is visible (and may not
> be able to see the blue additive pump not visible from the car pumps), 
> others will do an exaustive survey

Agreed.

IMHO basically the main reason why multi-tag standard (e.g. fuel:octane_98=yes,
fuel:diesel=yes, fuel:lpg=no) was invented is precisely because in
multi-value system it would have been impossible to mark the difference
between "this fuel is not present" and "it is unknown/unsurveyed if this fuel
is present here", i.e. it would make a pressure on mapper to either:
- invest a lot of time to map EVERYTHING, or
- better map NOTHING if they didn't have that time (in order not to create more
  confusion / false data)

e.g. if "fuel=octane_98;diesel" was tagged, it would be ambiguous - does
it mean that there there is no LPG, or that the mapper didn't care to survey
that separated area of fuel station where LPG is being held?

With multi-tag standard it is unambiguous, and users may map as much or as
little as they want, and other people can iteratively improve later according
to their preferences. 

E.g. if I just tanked diesel into my HGV on some fuel station, I can add tag
"fuel:HGV_diesel=yes" and go on my way (or mark "fuel:HGV_diesel=no" if I see
that this fuel station is useless for me), knowing that next time I need it
the map would be more useful to me and other HGV drivers, and *without*
having to take a walk and map every other type of fuel available to regular
car drivers (unless I want to and have time to kill)...

So, if it is tagged "fuel:lpg=no", it means there is no LPG there, if it is
tagged "fuel:lpg=yes" it means there is LPG there, and if "fuel:lpg=*" is
missing completely, it means it is (currently) unsurveyed (and should be
surveyed if one cares about LPG availability).

As a sidenote, another (much less important in practice, but potentially
problematic as number of values grew) advantage of multi-tag standard was
that the limit of max. 255 chars per tag is avoided)


-- 
Opinions above are GNU-copylefted.