Re: [I18nrp] Mappings for IDNA2008 ?

Patrik Fältström <paf@frobbit.se> Tue, 05 February 2019 13:00 UTC

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To: "Asmus Freytag (c)" <asmusf@ix.netcom.com>
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Subject: Re: [I18nrp] Mappings for IDNA2008 ?
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> On 5 Feb 2019, at 09:29, Asmus Freytag (c) <asmusf@ix.netcom.com>; wrote:
> 
>> On 2/4/2019 11:24 PM, Patrik Fältström wrote:
>>> On 5 Feb 2019, at 0:27, Asmus Freytag wrote:
>>> 
>>>> Are there any published IDNA2008 mappings?  As far as I can tell,
>>>> everyone uses one from UTS46 by default, and it's not very good.
>>>> 
>>> Examples of its badness, please.
>> Mapping of characters, including case folding, is LOCALE specific.
>> 
>>   
> That's not in contradiction to using a generic mapping for the 90% case and applying tailoring (on a per locale or other basis).
> 
> It may explain why it's bad to use a default WITHOUT adding tailoring, but does not explain why a particular generic mapping represents a "not very good" starting point for such tailoring.
> 

Let me try with a different explanation...

Depending on context (writing direction, locale, where the data in received etc) the application must for IDNA2008 FIRST make a conscious choice whether any mapping should happen (or just validation), and IF mapping is to happen, whether for example only NFC should happen, or case folding (locale dependent) etc.

One can not (IETF found when discussing IDNA2003) do everything “in one go”.

1. Mapping
2. Validation

   Patrik
> A./