[Tagging] Best practices regarding implied tags

Kevin Broderick ktb at kevinbroderick.com
Thu Sep 17 13:08:25 UTC 2020


+1.

Explicit tagging indicates a level of confidence not generally associated
with implicit tagging. While there's certainly an 'ad nauseum' level of
doing so (e.g. adding surface=paved, motor_vehicle=yes to highway=motorway
in the U.S. would be kinda silly, IMO), there are plenty of cases where a
primary tag generally implies something about the tagged object but doesn't
guarantee it. I'd point to the recent discussion of access= on driveways as
an example; while most driveways allow for certain types of access by
default, it's far from guaranteed—there may be a no-trespassing sign or a
locked gate, and explicitly indicating the lack of such in the access
tagging is helpful. (Adding the implied value without survey or other
definitive knowledge is not, as then you express a higher degree of
confidence than actually exists in the data).

On Wed, Sep 16, 2020 at 6:34 PM Paul Johnson <baloo at ursamundi.org> wrote:

> On Wed, Sep 16, 2020 at 5:20 PM François Lacombe <
> fl.infosreseaux at gmail.com> wrote:
>
>> Is that completely wrong or mappers could eventually add implied tags if
>> they want to?
>> The proposal currently states they are optional and it won't raise an
>> error if mappers add them beside mandatory tags.
>>
>
> No, it's not wrong to add implied tags explicitly.  It's actually
> encouraged in some cases where the implicit tag is not consumable by
> automated system (such as the "none" default for turn:lanes tends to be
> ambiguous between "you can't turn from this lane" and "you can't use this
> lane" and "there's an implicit but unspecified implication that isn't
> painted on the ground"), or access defaults (such as in the US where
> bicycle=* and foot=* varies a lot on highway=motorway)
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-- 
Kevin Broderick
ktb at kevinbroderick.com
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