Re: [Tagging] one feature one element

[Joseph Eisenberg]

>> *"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.
>
> I don't think it is an issue of replacing it. But where the location of
> the drinking water is unknown?

Right. It's great to map amenity=drinking_water on a node at the exact
position of a drinking fountain or water tap.

But if you want to say that a leisure=picnic_site has access to
drinking water without creating a separate node, then use the approved
and popular tag drinking_water=yes on the same area or node as the
picnic_site.

The key drinking_water has been used over 60,000 times and was
approved in a well-developed proposal back in 2014, so I picked this
example for the page.

But if there is a better example (eg atm=yes and amenity=atm?) feel
free to change it.

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Re: [Tagging] one feature one element

[Warin]

On 05/07/19 19:57, Mariusz wrote:

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.


I have done both - mapped a shop on the building way and in a different 
place, as a node inside a building way.


The advantages of having the shop as a node inside a building way .. if 
the shop moves it is much easier to move the node and the history is 
retained. I think I prefer the shop as a node  method in hind sight. 
Much easier to maintain.





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).


Some possible issues with that?
The fence is usually inside the boundaries of the land use.
The fence will have at least gates.
The fence may not be of a consistent height/construction ..



*"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.


I don't think it is an issue of replacing it. But where the location of 
the drinking water is unknown?



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Re: [Tagging] one feature one element

[Tobias Knerr]

On 05.07.19 11:57, Mariusz wrote:
> On 05.07.2019 07:05, Joseph Eisenberg wrote:
>> [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.

It's true that shop tags on building outlines are a common practice.
However, POI nodes inside buildings are likewise common. So I believe it
was a good idea for Joseph to remove this statement. It did present a
widely accepted practice as a "bad situation" in need of fixing, after all.

> It is fine to map multiple real objects with one osm element

It'd say it's ok as a shortcut during initial mapping, but it is far
from ideal. As soon as you want to add tags which only apply to one of
the features (you mentioned "start_date" or "operator" as two examples,
but of course there are more), using separate elements becomes necessary.

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

It wasn't properly fixed until the introduction of man_made=bridge –
that is, a separate OSM element for the bridge.

The bridge:name tag was only a band-aid for a single symptom of a deeper
issue. It did little to address the other symptoms, such as multiple
roads running across the same bridge, and tags other than name.

Tobias

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Re: [Tagging] one feature one element

[Jmapb via Tagging]

On 7/4/2019 11:17 PM, Joseph Eisenberg wrote:

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?

I can see the confusion here, but I think this rule still holds:
Normally linear features like barrier and highway will only be
interpreted as areas if tagged with area=yes. The presence of other tags
which imply area is not the same as area=yes.

But it's true that this usage verges on breaking the
one-feature-one-element rule -- unless you think of "fenced camp site"
as a single feature, which is a bit of a stretch.

Regardless, it's quite common to indicate a barrier around a 2D way by
tagging it with barrier=. I don't think it's genuinely ambiguous so I
doubt that it's going away any time soon, barring editor and bot
intervention. (I used to see fenced=yes... but only on pretty old
changesets.)


So I'd like to add a line that recommends to avoid mapping two
different "feature" tags on the same database object.


Which exactly are the "feature" tags? Everything on
https://wiki.openstreetmap.org/wiki/Map_Features ? Obviously building=
shouldn't be included, as it's often combined with other features. I see
cycleway= combined with highway= all the time. Same with sport= and
leisure=, tourism= and historic=. There are many other examples of
commonly used tag combinations, I'm sure.

If you want to try writing a narrower list of "top-level" keys that
should be mutually exclusive, give it a shot -- but I think that's going
to be a short list once we run through it and find all the useful
exceptions.

More likely to work would be: For certain keys, a list of other keys
that should not be used in combination. This list could appear as part
of each section on https://wiki.openstreetmap.org/wiki/Map_Features, or
as its own section on the https://wiki.openstreetmap.org/wiki/Key:*
pages. It might still be difficult to get consensus on these in many cases.

Jason


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Re: [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



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Re: [Tagging] one feature one element

[Joseph Eisenberg]

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  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  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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Re: [Tagging] one feature one element

[Joseph Eisenberg]

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  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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Re: [Tagging] one feature one element

[Warin]

On 05/07/19 03:11, marc marc wrote:

Le 04.07.19 à 18:26, Jmapb a écrit :

As far as I know, amenity=school is the *only* accepted landuse-esque
tagging for school grounds.

it's the perfect example of confusion between two different things.
if a school is located on the ground floor of an apartment, office,
or commercial building, believing that amenity=school is a landuse
is wrong.


Why?

The land is used by both the school and the other use.

Just as a high rise building with retail stores at the bottom and residential 
apartments at the top has 2 land uses.

I don't think it is 'wrong' .. just that OSM does not provide for 2 or more 
land uses of one area, and that is the bit that is 'wrong'.





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Re: [Tagging] one feature one element

[Jmapb]

On 7/4/2019 1:11 PM, marc marc wrote:

it's the perfect example of confusion between two different things.
if a school is located on the ground floor of an apartment, office,
or commercial building, believing that amenity=school is a landuse
is wrong. in this case amenity=school (as a node or a way) only
describe the localisation and/or the level, not the landuse.
It is also wrong to believe that amenity=school implies
landuse=residential (because the landuse of an office building
is not residential)
even if the majority of schools have the same extent between
amenity=school and landuse=school (or equivalent), there are many cases
that show that sometimes it is different and that therefore the 2 tags
are not synonymous


I definitely think the recommendation to add landuse=residential to
amenity=school is unsound. Even for a school surrounded by a residential
area, I wouldn't consider the school grounds themselves to be residential.

My preference with school grounds would be:
 - Just one school? Continue to use amenity=school as a pseudo-landuse,
and put all of the relevant tags for the school (name, etc) on that way.
If you want to add landuse=education/school, fine, but
landuse=residential makes no sense.
 - Two or more schools? Tag the grounds with landuse=education, and add
the individual amenity=school (plus name, etc) tags on
nodes/buildings/areas, as appropriate.

J


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Re: [Tagging] one feature one element

[Jmapb]

On 7/4/2019 12:48 PM, Martin Koppenhoefer wrote:

you could also overlap (multipolygons or not) different schools when
they share the indoor space, but if there are distinct names for the
campus and the schools, we would need a tag for the campus which we
don’t have yet, AFAIK
Cheers, Martin


Yeah I'd happily do that if I had a reasonable idea about the indoor
layout, as mercurial as that might be. But in general that's not
possible, and I wouldn't want to map multiple amenity=school ways across
the entire campus because it would imply that a school occupies the
entire footprint, which is unverifiable and highly unlikely.

(My second example above actually does have a name for the entire
campus. It's a single building though, so I just used it as the building
name. For multi-building campuses I could name a multipolygon... but I'd
much prefer a landuse.)

J


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Re: [Tagging] one feature one element

[marc marc]

Le 04.07.19 à 18:26, Jmapb a écrit :
> As far as I know, amenity=school is the *only* accepted landuse-esque
> tagging for school grounds.

it's the perfect example of confusion between two different things.
if a school is located on the ground floor of an apartment, office,
or commercial building, believing that amenity=school is a landuse
is wrong. in this case amenity=school (as a node or a way) only
describe the localisation and/or the level, not the landuse.
It is also wrong to believe that amenity=school implies 
landuse=residential (because the landuse of an office building
is not residential)
even if the majority of schools have the same extent between 
amenity=school and landuse=school (or equivalent), there are many cases 
that show that sometimes it is different and that therefore the 2 tags 
are not synonymous
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Re: [Tagging] one feature one element

[Martin Koppenhoefer]

sent from a phone

> On 4. Jul 2019, at 18:26, Jmapb  wrote:
> 
> But what I'm faced with very often in NYC is a single campus,
> sometimes with one building and sometimes more, that's shared by several
> schools -- and there's no accurate way to divide up the buildings.


you could also overlap (multipolygons or not) different schools when they share 
the indoor space, but if there are distinct names for the campus and the 
schools, we would need a tag for the campus which we don’t have yet, AFAIK

Cheers, Martin 
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Re: [Tagging] one feature one element

[Jmapb]

On 7/4/2019 6:33 AM, Warin wrote:

On 04/07/19 20:09, Janko Mihelić wrote:

I've been tagging it with an empty amenity=school polygon around
everything, and then two points with amenity=school + name=* + all
the other specific tagging.


I too have used similar.
Usually a polygon/way with one school on it and then a node inside it
for the other school, or schools if more than one.



But if mapped like that, a data consumer would see 3 schools. I like
your solution with overlapping multipolygons.

Janko


On one occasion I have separated then into 2 separate ways, I am
certain that some of each area will be shared from time to time, but
it seams to be a good compromise. Every other time I have not had any
reasonable chance of doing this.

Most people would consider amenity=school to be a land use, along with
other tags such as leisure=recreation_ground.


As far as I know, amenity=school is the *only* accepted landuse-esque
tagging for school grounds. https://wiki.openstreetmap.org/wiki/Landuse
clearly says to tag school grounds as amenity=school, possibly along
with landuse=residential.

Which is unfortunate IMO; I would definitely support a
landuse=education/school tag. These are both in use, =school being about
10 times as popular, but they're not documented and don't render.
(Personally I'd prefer =education because of course somewhere there are
grounds that are shared by both a school and a college.)

For now, I like Martin's multipolygon solution -- for instances where
the indoor portions of the schools are clearly in different buildings or
areas. But what I'm faced with very often in NYC is a single campus,
sometimes with one building and sometimes more, that's shared by several
schools -- and there's no accurate way to divide up the buildings. Even
if someone could do detailed indoor mapping, the rooms and offices will
shift around depending on season, politics, and student population --
and some facilities, both indoor and outdoor, are shared by some or all
of the schools.

For now I've simply placed amenity=school nodes inside the most
prominent building and ignored the grounds. But it's unsatisfactory.

Examples:
https://www.openstreetmap.org/#map=19/40.68394/-73.98011
https://www.openstreetmap.org/#map=19/40.66937/-73.97840

If it were possible to do a "multipolygon" where one element was a node,
that world be similar solution to Martin's -- but that's really too
confusing to endorse.

I don't love the idea of marking the grounds with one amenity=school and
using nodes for the others, unless there's clearly one main school and
some less prominent schools. And I certainly don't like the idea of more
amenity=school features than there are schools.

Without a landuse=education area, I don't really see a good way to tag
the grounds in these situations. I'm tempted to go ahead and start
adding these but I'm a bit of a wiki thrall.

(Here's a related post on the German user forum:
https://forum.openstreetmap.org/viewtopic.php?id=59981 "Zwei Schulen auf
einem Gelände" and one on the help forum:
https://help.openstreetmap.org/questions/57320/two-schools-sharing-same-building-and-ground
. In both cases the proposed solution is landuse=school.)

Jason


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Re: [Tagging] one feature one element

[Warin]

On 04/07/19 20:09, Janko Mihelić wrote:
I've been tagging it with an empty amenity=school polygon around 
everything, and then two points with amenity=school + name=* + all the 
other specific tagging.


I too have used similar.
Usually a polygon/way with one school on it and then a node inside it 
for the other school, or schools if more than one.



But if mapped like that, a data consumer would see 3 schools. I like 
your solution with overlapping multipolygons.


Janko


On one occasion I have separated then into 2 separate ways, I am certain 
that some of each area will be shared from time to time, but it seams to 
be a good compromise. Every other time I have not had any reasonable 
chance of doing this.


Most people would consider amenity=school to be a land use, along with 
other tags such as leisure=recreation_ground.




čet, 4. srp 2019. u 09:58 Martin Koppenhoefer > napisao je:


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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Re: [Tagging] one feature one element

[Janko Mihelić]

I've been tagging it with an empty amenity=school polygon around
everything, and then two points with amenity=school + name=* + all the
other specific tagging. But if mapped like that, a data consumer would see
3 schools. I like your solution with overlapping multipolygons.

Janko

čet, 4. srp 2019. u 09:58 Martin Koppenhoefer 
napisao je:

> 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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[Tagging] one feature one element

[Martin Koppenhoefer]

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 


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