Re: [precis] Category changes with Unicode 6.3

John C Klensin <klensin@jck.com> Wed, 16 October 2013 13:47 UTC

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Date: Wed, 16 Oct 2013 09:46:51 -0400
From: John C Klensin <klensin@jck.com>
To: =?UTF-8?Q?Patrik_F=C3=A4ltstr=C3=B6m?= <paf@frobbit.se>, =?UTF-8?Q?=22Martin_J=2E_D=C3=BCrst=22?= <duerst@it.aoyama.ac.jp>
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Cc: idna-update@alvestrand.no, precis@ietf.org
Subject: Re: [precis] Category changes with Unicode 6.3
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--On Wednesday, October 16, 2013 10:16 +0300 Patrik Fältström
<paf@frobbit.se> wrote:

> Yeah, I had to do it anyways -- as I am expert reviewer of the
> IANA tables. New versions of the IANA tables where created by
> IANA the other day, and I just approved them as they match my
> own calculations. I.e. we have two completely independent
> implementations of IDNA2008 (one at IANA, one that I have --
> see link below) and I compare the output of the two. If the
> output matches, then we are pretty sure we are correct.

This is great.   To a considerable extent, it reinforces the
utility and importance of the IDNA2008 approach.   YOu (and
IANA) reapply the rules to a new version of Unicode, verify that
nothing  significant has changed and your results are the same,
and we move on.

In addition, because mapping is defined on top of those rules
and the collection of allowable code points they create, we
don't end up with different profiles for different domains or
applications.

It remains to be seen whether the PRECIS approach will work as
well.  On the one hand, generation rules have replaced the
normative Stringprep table.  On the other, that system leads,
not to a definitive list but to string classes that are then
profiled, potentially on an application-by-application or even
implementation-by-implementation basis, to yield actual
practices.  Different behavior in different applications may be
inevitable but it is certain that it will confuse at least some
users.  And, because different profiles will address different
parts of the basic PRECIS code space, it is possible that the
same evaluations that are run against the generation rules for
IDNA (and exceptional adjustments added if needed) will need to
be performed for each profile, resulting in temporal
instability.    Perhaps it will all work out and the profiles
will be completely stable, but it is hard to be completely
confident about that.

best,
   john