Re: [I18ndir] [art] Modern Network Unicode

John C Klensin <john-ietf@jck.com> Wed, 10 July 2019 23:34 UTC

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Date: Wed, 10 Jul 2019 19:33:52 -0400
From: John C Klensin <john-ietf@jck.com>
To: Asmus Freytag <asmusf@ix.netcom.com>, i18ndir@ietf.org, Carsten Bormann <cabo@tzi.org>
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Subject: Re: [I18ndir] [art] Modern Network Unicode
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--On Wednesday, July 10, 2019 16:00 -0700 Asmus Freytag
<asmusf@ix.netcom.com>; wrote:

> On 7/10/2019 12:09 AM, John C Klensin wrote:
>> For the record, I do have one other concern.  The examples
>> above use extended Latin script.  Because of its NVT origins,
>> much of 5198 makes assumptions about that script or scripts
>> closely related to it.  If you are doing something for this
>> century and beyond, you should really think carefully about
>> the implications of scripts that are very different.
> 
> There are a few scripts where un-normalized text is
> "preferred" by the user community over NFC. In some cases, the
> most natural ordering of combining marks does not match NFC's
> canonical ordering. I other cases, NFC does not compose some
> sequences while local user communities strongly prefer the
> precomposed code points (e.g. Bengali).
> 
> Those scripts would be an exception to John's statement: " NFC
> is also a close approximation to what any sensible terminal
> driver or IME is going to produce natively from a plausible
> keyboard layout for the relevant script", a statement that
> otherwise holds well.

Indeed.   The explanation is also more detailed that I had time
for, and better than I would have written if I had tried, as to
why encouraging everything to be forced into NFC before
transmission is probably unwise.

    john