Re: [idn] call for comments for REORDERING

[David Hopwood <david.hopwood@zetnet.co.uk>]

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Martin Duerst wrote:
> At 15:43 01/10/10 +0900, Soobok Lee wrote:
> >From: "Martin Duerst" <duerst@w3.org>
> 
> > > The additional complexity introduced by reordering is a very
> > > serious problem. It is true that this complexity is somewhat
> > > similar to the complexity of e.g. nameprep or conversion from
> > > a legacy encoding. However, on many platforms, both conversion
> > > from a legacy encoding as well as many aspects of nameprep
> > > are available as libraries, and are used for other purposes.
> >
> >Current Windows 98,2K,XP and Linux  contain   NFKC codes ?
> 
> No. My personal preference would be for NFC, anyway, because
> most of the additional mappings in NFKC are not really useful,
> because they are from characters that are quite difficult
> to type in. So these characters could just be forbidden rather
> than mapped. The only exception I know is full-width ASCII,
> which could either be included in the nameprep mapping step,
> or could be done as a front-end 'quality of implementation'
> step (similar to how the ideographic fullstop is currently
> treated).

I absolutely agree with this - I've been preparing a detailed
rationale for using NFC in preference to NFKC, that considers all
the categories of compatibility mappings. I'll post it tomorrow.
An important consideration is that by disallowing a larger set of
characters, we can avoid the need for "additional foldings" - i.e.
it is possible to just apply NFC and the standard Unicode case
folding, in either order, which strengthens your argument above
about being able to use existing libraries.

> Displaying ACE when nothing else is available is acceptable
> as a 'best-effort' solution. But it is very far from a good
> solution, and designing the rest of IDN for this doesn't
> make sense.

A better solution for cases where a name can't be displayed in
its original script, is to use a transliteration (which unlike an
ACE encoding, has a chance of actually meaning something to end-
users). I have a proposal for a new RR that allows translations
and transliterations of a name to be looked up, and provides a
way to encode the language and script of each name. This is a new
feature that is independent of the rest of IDN; it doesn't break
the basic model of DNS as an untagged namespace.

- -- 
David Hopwood <david.hopwood@zetnet.co.uk>

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