I have honestly no clue, because I do not have any data model available - nor for OSM sec, nor for Nominatim.
But I would definitely advise to use ISO3166-2 codes if possible; so :
NL for the Netherlands / Nederland
AW Aruba
CW Curacao
SX St. Maarten (note: ‘Dutch’ part only !)
Ratio: using ISO3166-2 allows for coupling with other ISO standards like curency code, internet domain code etc.
Just for more (or less clarification: the former Netherlands Antilles islands of Bonaire, Saba and St. Eustatius are ‘special administrative units’ of the Netherlands / Nederland, but are not part of any province, do not belong to the Schengen -area and do not have the Euro as currency (rather the US Dollar). On these 3 islands, former Netherlands Antilles laws and tax regulations are being transformed to Netherlands ones in a gradual process.
Just an idea: Although Nominatim correctly determines address tags for Curaçao as CW, it still favours the higher ranked “Koninkrijk der Nederlanden” relation for ISO code and country display. Same for the other members of that relation.
Should relation # 2323309 (named ‘Nederland’) (admin level 2) not be labelled ‘Koninkrijk der Nederlanden’ indeed ? It is currently just named ‘Nederland’ but it seems to include Curacao, Aruba and St. Maarten (all admin level 3). After all, there is an IMHO correct relation for ‘Nederland’ (consisting of Europe mainland Nederland plus correctly Bonaire, Saba and St. Eustatius) being # 47796.
Whether that helps the postal code problem is another question…
Do I see here that Admin Level 3 has a description of ‘Kingdom of the Netherlands, cons’ - what does the ‘cons’ -part mean ?
It looks like ‘Kingdom of the Netherlands’ should be level 2, and ‘the Netherlands’ level 3.
Likewise int_name ‘Koninkrijk der Nederlanden’ on level 2, ‘Nederland’ on level 3.
And additionally I wonder whether the quoted ISO-3166 -codes should not be put on level 3 instead of level 2.
Most name:xxx descriptions currently under level 2 should also be level 3, I fear … (and on some of them, like the DAnish ‘Holland’ for level 2 vs. ‘Nederland’ for level 3 I have serious doubts).
Are you able - and willing to change some of them? Starting with some names? and ignoring the translations at first?
i think, its better a local mapper will do that.
no, they are looking ok to me. ISO-3166-1 is for countries. But level 3 needs additional ISO-Codes ISO3166-2, i think. i’ll check that at the ISO webpage.
One of the basic issues here is the question: ‘What is a country ?’. The UN (or at least it’s statistical department) defines it differently as others. The UN wants a country in principle to have a permanent representation at the UN. ISO is more relaxed and pragmatical. However, in the Kingdom of the Netherlands (the level 2 thus) there are 4 separate countries (on level 3 thus) where 1 of these takes care of all foreign business on behalf of all 4. That makes Aruba, Curacao and St. Maarten not really totally a country according to UN norms, with the result that those 3 have both a separate 3166 code (like ‘AW’ for Aruba) AND a (another) 3166-2 code, like ‘NL-AW’. Confused ? You would be right. Sag mal: would this be causing the postal code problems ?
That Bonaire, Saba and St. Eustatius as sub-entity of Nederland have a common separate country code ‘BQ’ is not logical at all - certainly not from UN point-of-view. But they may have been needed for another reason: those islands have the USD as official currency, and otherwise (being level 2 -labelled as ‘NL’) a lot of computer systems might have assumed they would use EUR which could cause issues in banking and payment systems (this is a true story, actually).
I’m fully willing to clean-up my country (administratively); but only after consulting the NL user forum.