[Tagging] one feature one element

Joseph Eisenberg joseph.eisenberg at gmail.com
Fri Jul 5 05:05:55 UTC 2019


I've removed this statement from the page because it leads to
ambiguous data and directly contradicts the One feature per one
element rule

[Examples of bad situations:] "An area object representing a
single-use building with a point object inside it. Move the tags to
the area object and delete the point."

If the same feature is tagged with building=* and another feature like
shop=* or office=*, it's ambiguous whether other tags like name=*
represent the building itself or the other feature.

While it's common to tag single-use buildings in this way, it isn't
the best practice, because of this ambiguity. Users should not be
encouraged to delete all single node objects within buildings without
carefully considering each of the tags.

Joseph


On 7/5/19, Joseph Eisenberg <joseph.eisenberg at gmail.com> wrote:
> I agree that this page could be improved. Until now it hasn't
> mentioned the problems with tagging multiple features on one database
> object.
>
> This can be difficult for database users, for example this comment at
> the Openstreetmap-carto github page:
> https://github.com/gravitystorm/openstreetmap-carto/pull/3796
>
> "This is a part of a broader problem - how to deal with objects that
> have multiple properties. I've seen objects with all building= shop=
> office= and amenity= defined"
>
> We've also had problems with features tagged "tourism=camp_site" or
> "landuse=meadow" plus "barrier=hedge" or "barrier=wall". Is the
> barrier supposed to be an area or a linear feature in this case?
>
> So I'd like to add a line that recommends to avoid mapping two
> different "feature" tags on the same database object.
>
> But we will have to mention that building=yes plus amenity=clinic and
> landuse=meadow plus barrier=fence are commonly used, even if they are
> problematic.
>
> Joseph
>
> On 7/4/19, Martin Koppenhoefer <dieterdreist at gmail.com> wrote:
>> The one feature page states:
>> More than one of something on the same site e.g. two schools sharing
>> grounds. Normally if the schools are separate they would have separate
>> neighbouring grounds, but if the only thing defining a separation between
>> two schools is their buildings, then the containing area should be tagged
>> with a suitable landuse=*, and the buildings tagged individually.
>>
>> from
>> https://wiki.openstreetmap.org/wiki/One_feature,_one_OSM_element#Examples_of_bad_situations
>>
>> I don’t believe this is common practice, e.g. there isn’t even a landuse
>> value for schools.
>> I would rather tag 2 schools with distinct buildings and shared grounds as
>> 2
>> overlapping amenity=school areas with the “other buildings” (those of the
>> other school) excluded via multipolygon inner roles.
>>
>> If we did like currently suggested in the wiki it would also loose the
>> information about the grounds (only the buildings would result as
>> schools).
>>
>> Cheers, Martin
>>
>>
>> sent from a phone
>



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