Re: [idn] NFC vs NFKC

["Mark Davis" <mark@macchiato.com>]

Either deletion, prohibition or producing fillers can be accomplished, if
desired, by adding mappings to "D. Mapping Tables" in
http://www.ietf.org/internet-drafts/draft-ietf-idn-nameprep-06.txt. And this
is *without* having to change anything else in nameprep. For example, for
U+3131 HANGUL LETTER KIYEOK here are the three options:

Deletion:
3131; ; Deletion

Prohibition:
3131; 0000; Prohibition

Additional folding
3131; 1100 1160; Additional Folding

In the last case, the medial filler is added. It is sufficient to do this
only for the initials, since that prevents any syllable formation. However,
if one wanted, the initial filler could be added before medials, such as for
U+314F HANGUL LETTER A below (or initial and final fillers could be added
before finals).

Additional folding
314F; 115F 1161; Additional Folding

Mark

—————

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[http://www.macchiato.com]

----- Original Message -----
From: "Soobok Lee" <lsb@postel.co.kr>
To: "Yves Arrouye" <yves@realnames.com>; <idn@ops.ietf.org>; "Martin Duerst"
<duerst@w3.org>
Sent: Thursday, October 25, 2001 09:04
Subject: Re: [idn] NFC vs NFKC



----- Original Message -----
From: "Martin Duerst" <duerst@w3.org>
 >
> Hangul domain names in KS C 5601 would normally be encoded as
> precombined syllables. KS C 5601 provides about 2300 of them,
> the ones most often used. Users who want to used other Hangul
> syllables won't use non-conjoining Jamo (compatibility Jamo),
> because they will be displayed one Jamo at a time.
>
> In the nameprep design team, we discussed some cases where users
> might want to use sequences of independent consonant Jamo. There
> are a few web pages with some examples of these, but not too many.
> We are not sure whether they should be allowed in domain names or
> not, and if they are, how they should be represented.
>

Current windows 98 and above  support only  compatibility Jamo, does
not support "conjoining jamo + filler" sequence for isolated jamos
which are often found in informal texts/business names.
No display and No input method for "conjoining jamo + filler" in
windows O/S.

Compatiliby Jamo became the defacto standard for isolated jamos
inadvertantly and contrary to the intent of ISO Korean representatives and
UTC members.

NFKC maps Compatiblity Jamo to conjoining jamos withOUT fillers.

Nameprep's positions on NFKC's problematic handling of compat jamos
should be clarified. Two alternatives.

  1) NFC is used instead
  2) NFKC is used but bypass all characters from the compatibility jamo
block

Soobok Lee


>
> >[Edit] Is that because nobody uses these anymore, and so you would not
> >expect a modern invention like IDN to appear in an anachronic way? Is
that
> >the case with all LEGACY characters?
>
> I don't want IDN to carry unnecessary legacy compatibility
> baggage. If it turns out that something really helps the user
> (e.g. for the full-width Latin letters), I have nothing against
> mapping them. But I don't think it's a good idea to map a
> wholesale 3000, most of them not really used and very difficult
> to type in, just to get a few dozen mapped the right way.
> We can easily do the later without having to do the former.
>
>
> Regards,   Martin.
>