Orphaned building parts

[JsfasdF252]

What steps will reproduce the problem?

1. Add a closed way.
2. Tag it with building:part=*.
3. Run the JOSM validator

What is the expected result?

The validator should issue a warning/error about the building part being disjoint from any building.

What happens instead?

No such warning appears.

Please provide any additional information below. Attach a screenshot if possible.

I have made the error of orphaned building parts twice.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-04-27 20:35:33 +0200 (Tue, 27 Apr 2021)
Build-Date:2021-04-27 21:58:39
Revision:17833
Relative:URL: ^/trunk

Identification: JOSM/1.5 (17833 en) Windows 10 64-Bit
OS Build number: Windows 10 Home 2009 (19042)
Memory Usage: 989 MB / 989 MB (118 MB allocated, but free)
Java version: 1.8.0_281-b09, Oracle Corporation, Java HotSpot(TM) Client VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1080 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1080
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: Cp1252
System property sun.jnu.encoding: Cp1252
Locale info: en_US
Numbers with default locale: 1234567890 -> 1234567890
Dataset consistency test: No problems found

Plugins:
+ ShapeTools (1240)
+ apache-commons (35524)
+ apache-http (35589)
+ areaselector (368)
+ austriaaddresshelper (1597341117)
+ buildings_tools (35669)
+ ejml (35458)
+ gridify (1606242219)
+ imagery_offset_db (35640)
+ jna (35662)
+ log4j (35458)
+ mapwithai (1.7.1.5)
+ reltoolbox (35640)
+ turnrestrictions (35640)
+ utilsplugin2 (35691)
+ wms-turbo-challenge2 (35562)

Tagging presets:
+ https://raw.githubusercontent.com/osmlab/name-suggestion-index/main/dist/presets/nsi-josm-presets.min.xml

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/MapWithAI&zip=1

Last errors/warnings:
- 00012.054 E: Failed to locate image 'MapWithAI'
- 65343.835 E: java.lang.IllegalStateException: JOSM expected to find primitive [way -103396] in dataset but it is not there. Please report this at https://josm.openstreetmap.de. This is not a critical error, it should be safe to continue in your work.

[GerdP]

What exactly is needed to detect that a building:part is not disjoint? My understanding is that you can have valid building:part objects which are outside of any building=*, e.g. when there is a bridge between two buildings?

[skyper]

I would say, it should at least share one side (two consecutive nodes) with another building:part=* or building=* if completely outside and two non-consecutive nodes when crossing another building=* or building:part=*. Additional I expect some building:min_level=* on both kinds of building:part.

I am not sure if a building relation is always needed for these constructions with building:part=* outside building=*.

[Klumbumbus]

Replying to GerdP:

My understanding is that you can have valid building:part objects which are outside of any building=*, e.g. when there is a bridge between two buildings?

This is not how it is meant to be. The wiki page of bulding:part says: "building:part=* areas should be always within a separate building=* area representing the entire building. "
Therefore e.g. the ​Petronas Towers have ​https://www.openstreetmap.org/way/279944536 sourrounding all and the different parts, e.g. the bridge ​https://www.openstreetmap.org/way/137396365.

[skyper]

Sadly, I never understood the whole system of building=*, building:part=* and type=building 100%.
On one hand, I need the ground level outline and count the levels from there, on the other hand, I have complex buildings which might consist of several building=* in OSM and have bigger outlines above and/or below ground level. How to solve these situations without "building inside building"?
Additionally, MPs are invalid if members share segments which makes it more complicated, especially, with buildings with "holes" where the building:part=* are already MPs. I failed on ​this one so far.

What makes the situation even more dubious is that there are all kinds of links on ​Key:building and ​Buildings but none to ​Key:building:part.