[Tagging] 'Unknown' value.

Adam Snape adam.c.snape at gmail.com
Mon Feb 5 19:06:07 UTC 2018


Is 'unknown' really such an unusual and undesirable as an access tag? I
thought it was long-established, if not especially common. If the issue is
a lack of Wiki documentation that is easily solved.

I think that highway=footway foot=unknown adds a useful level of nuance.
For example a routing engine could choose to avoid such routes where it
would route over a footway by default. Of couse we could produce this
result by tagging foot=no, but if we don't know that pedestrians actually
aren't allowed that would be incorrectly tagging for the router.
foot=unknown could be considered an implicit fixme in the same way as
highway=road is, but also have teh benefit of being useable directly by
data consumers (if they chose to use it) unlike the free-form text
contained in notes and fixmes.

More generally, wherever an absence of a particular tag is taken to imply
something is or isn't present then a tag of something=unknown does have a
valid and worthwhile meaning distinct from no tag at all. .


On 5 February 2018 at 16:46, OSMDoudou <
19b350d2-b1b3-4edb-ad96-288ea1238eee at gmx.com> wrote:

> I'd rather use fixme and note tags instead of encoding uncodified
> information in well-established tags.
> The wiki page [1] explains a bit the difference: "The fixme key allows
> contributors to mark objects and places that need further attention. These
> can be in the form of a "note to self" or request for additional mapping
> resources. Its distinction from note=* is that fixme is only to express
> that the mapper thinks there is an error, while note might be information
> to other mappers."
> If it's reasonable to think tagging can be improved (e.g. initial tagging
> was a bit rushed and better tagging is expected based on site survey or
> imagery), than a fixme note looks suitable.
> In the case you describe ("nothing suggesting that further survey will
> reveal what the legal situation is"), a note looks suitable to document
> there was a site survey and explain why "it was obvious that it was not
> obvious" (that is to say: explaining the elements causing your perplexity
> conveys much richer information than tagging "unknown").
> And you could also start a discussion on the mailing list and link to it
> from the note, so other mappers are aware of the discussion and can
> contribute.
> [1] https://wiki.openstreetmap.org/wiki/Key:fixme
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