A closed way should have a "building" key once it has a "building:..."

There is something I do not understand.
I found some closed ways representing buildings. Like this one:


It’s building, but it does not have a “building” key. I assume that this is why http://www.openstreetmap.org does not render it as a building?
It only has a “building:levels” tag.

Should a building which has a “building:…” key (like: “building:levels”, “building:fireproof”, “building:architecture”…) ALWAYS have a “building” key as well? At least “building=yes” tag?

edit: here is Google Street view of the upper building.

That building has a tag: landuse=construction. Can that be the problem?

Thank you for the quick reply whturner!

Where can I see that tag?
The upper link shows only three keys: “building:levels”, “note” and “source”:


Every way should normally have a main tag. None of building:levels, source, nor note, are main tags.

Note, however, that my reading is that building:part should not have building tag, although there should be a way or relation covering the whole footprint of the building, that does have a building tag.

What concerns me more on this one is the source. It is definitely a broken link, and, whilst my German isn’t good enough to work out the details, I strongly suspect it is an illegal import of a copyright map (possibly a shopping centre plan??).

You have to look at the outer rim of the gray area: Way: Kornmarkt-Arkaden (340292514)

There is no landuse tag on the way in question.

There is a landuse tag on the enclosing area: http://www.openstreetmap.org/way/340292514

The source link is valid, but doesn’t seem to provide enough information to allow anything other than the name to be derived and looks to be from a place where the necessary database rights releases wouldn’t be given.

Tags on wholly enclosing ways do not propagate to the enclosed way.

In practice, one has to use a certain amount of common sense in determining whether inner areas cut holes in outer ones, as, for example, amenity=school within landuse=residential, is understood to cut a hole in the residential area,

In this case, I would suggest that both inner and outer ways should have been landuse=construction, but should have had different construction tags indicating what is being constructed. I think there is a trend from landuse=construction; construction=building to landuse=construction ; construction:building=shops, however, I’m not fully up to date on lifecycle prefixes, and don’t want to research the details just to answer this question.

Thank you for the replies!

I learned something new today!

Where can I find more information about: “main tags”?

Why the “building” key shouldn’t be used?

I thought that this was not required when the way is used to construct a multi polygon.

[Edit: improved grammar]

building shouldn’t be used with building:part because the building as a whole should be represented as its own way or relation. 2D renders will generally ignore building:part… If 2D renders only had building:part to work with, they would render lots of boundary lines that didn’t represent boundaries between buildings.

Thank you Hadw and Escada.

Where can I find information about “main tags”? I googled but was not successful.

I forgot multipolygon cases.

I don’t think you will find a definitive list of main tags. Whilst you could get a subset by looking at the style sheets of renderers, there will be specialist cases that are not known to the commonly used styles.

I suspect the main use of the term is in diagnosing incorrect tagging, i.e. there are references to “no main tag”, but not to “main tags”.

Thank you for the reply hadw.
But I didn’t understand you. If “no main tag” term exists, how come at least an approximate list of “main tags” does not?

Think about the thing as a real world item not just as a piece of XML. For example, picking somewhere entirely at random, It’s obvious what https://www.openstreetmap.org/node/2169282264 is because it’s tagged “amenity=fast_food”. However if it had only had “cuisine=chinese” then it wouldn’t be. Sure, it’s food-related, but is it a restaurant or something else?

Thank you SomeoneElse.

Hm. Let’s say I take the tag: “amenity=studio”, can this be considered as a “main tag”, or not?
Because we do not know whether this is a TV, radio, or recording studio?

Did I understand that correctly or not?

That’s a good question. With “amenity=studio” a quick sample of the data suggests that it’s all you’re going to get in many cases: http://overpass-turbo.eu/s/kuz . Unfortunately you can’t rely on the wiki for how tags are used; you need to look at actual tag usage. In the case of amenity=studio, someone or something trying to infer the type of https://www.openstreetmap.org/way/302036007 and https://www.openstreetmap.org/way/97203144 might have to look for something like “BBC” or “FM” in the names and guess based on that.

The people who tagged both of those two items thought that they’d added a main tag, but as you say, it’s not immediately clear from the tagging exactly what sort of studio it is.

Thank you for the useful reply and examples SomeoneElse!
I may need some time to wrap my head around this “main tag” thing. Still your example definitively helped me in clearing some doubts.