On 7/23/2018 5:56 PM, Martin Koppenhoefer wrote:

On 23. Jul 2018, at 17:08, Jmapb <jm...@gmx.com> wrote:

woke up to the conclusion that the attached/detached/semi-detached distinction 
is not a great use of the building tag. As mentioned by André, we can literally 
see on the map if these house footprints are attached via shared party wall.

it is not possible to do it reliably for terraced houses, because they are not 
only characterized by being attached.

This is true. Once a terrace has been converted from a single building=terrace way to a row of building=house ways, there's no sure way to distinguish it from a group of same-sized adjacent non-terrace houses. If we want to be able to pinpoint terraces, we should leave them as building=terrace ways. The wiki, though, specifically encourages breaking them up into houses.

Is it important to be able to query the map for terraces? If so, the wiki should change. Change the text to favor a single building=terrace way... or encourage a value like building=terrace_house when dividing them up into individual residences. But my guess is that the number of terraces already chopped up into building=house is so large that this would be futile.

So there's really no need to describe the attached-ness using the building tag. 
.... So the building tag is freed up to describe the characteristic style of 
the building  -- hut, shed, bungalow, house, apartments, villa, static_caravan

if you agree with the list above it seems more consistent not to drop detached 
in favor of residential; detached, semi-detached and terraced are all subtypes 
of houses, there is some overlap with bungalows and villas.

I don't consider that list to be canonical, just rattling off some of the more popular typologies. But in my mind, if the attached-ness can be visually seen on the map and geometrically determined by examining adjacent ways (admittedly this would be a complex query -- can't even begin to think how I'd code that in overpass) there's no need to crowd that info into the value of the building tag.

Mainly, I'm doubting the need for building=detached -- it's a house, and if it doesn't share a party wall with another building, then clearly it's a detached house. But it's also true that the word "detached" evokes a certain style of building, and if mappers think it's a good value to describe a particular building, I'm not going to argue, or advocate for retagging.


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