[Tagging] one feature one element

[Mariusz]

On 05.07.2019 07:05, Joseph Eisenberg wrote:
> 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."

This is common and widly accepted practice. Don't try to change mappers 
behaviour by editing wiki.

Also, there is no contradiction.  From wiki: "It means one on-the-ground 
real world feature should be mapped with only one OSM element. " That it 
- no multiple osm objects for one real world feature.
It is fine to map multiple real objects with one osm element, especially 
if you don't have enough data to map them seperately.

> 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.

Nothing new, this problem already existed with roads and bridges and was 
fixed by putting bridge name into bridge:name tag.

> 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.

That's true. POI and building may have more identical tags, for example 
"start_date" or "operator".


Moreover, you recently edited many times 
https://wiki.openstreetmap.org/wiki/One_feature,_one_OSM_element and 
some newly introduced things are controversial:
*"Ideally, every OSM element or object should be tagged with only one 
main feature tag, to represent a single on-the-ground feature."

I've never heard of such rule. It doesn't seemed to be correct. It is 
against KISS principle and it is not how mappers map.
For example, there is nothing wrong in placing tags "landuse=industrial 
+ barrier=fence" on one osm way. Doing it as 2 ways would even give you 
a warning in JOSM (ways in the same position).

*"For example, use the feature leisure=picnic_site with the property tag 
drinking_water=yes, instead of using the separate feature tag 
amenity=drinking_water on the same node or area."

This example is a bad idea and mappers shouldn't be encouraged to do so. 
amenity=drinking_water is far more popular tag and replacing it with 
drinking_water=yes may hurt data consumers.


Mariusz