Subject: Re: [idn] WG Update

From: [email-masked]
Date: Wed, 10 Oct 2001 03:04:19 EDT

In a message dated 2001-10-09 23:12:59 Pacific Daylight Time, 
[email-masked] writes:

>> To say that UTF-8 does not preserve case distinctions is complete
>> nonsense.  It is the nameprep stage that folds away case distinctions
>> (for better or worse).
>
>                   If  you mean casing of  Latin characters , you may be
>  right. but you can try the characters in (u+F94D , u+6dda), (u+F950, 
u+7e37)
>  that are compatibility CJK ideograph characters in www.unicode.org .

Neither the compatibility CJK ideographs nor any other CJK ideographs have 
"case" in the sense that bicameral alphabets like Latin, Greek, and Cyrillic 
have "case."  U+F94D and U+6DDA are not upper-case or lower-case forms of one 
another.  The great majority of the compatibility CJK ideographs, and 
specifically the two L.M. Tseng cited, exist solely for round-trip conversion 
from a legacy encoding.

>  If these characters are mapped to single one code point like the  case 
mapping
>  in ASCII , you can not use UTF-8 to do case-like-insensitive comparation 
and
>  to keep case-prserving .  The difference come from the relative to LDH-DNS 
.

Nothing in Unicode or ISO/IEC 10646, and certainly nothing in UTF-8, maps the 
two characters in such a pair to a single code point.  The standard 
cross-references the compatibility characters to the "real" characters, but 
in informative notes only.

>                  I don not against UTF-8 , but AMC-ACE-Z  can support
>  case-code- mapping and case-preserving-after-code-mapping and
>  case-sensitive-comparation all coexisted. It is an intergreted properties 
in
>  LDH-DNS.

I thought nameprep was the mechanism that handled equivalencies like this.  
If AMC-ACE-Z *without nameprep* can equate U+F94D with U+6DDA, it is a lot 
more complicated and requires much larger tables than Adam is letting on.

I suspect the real comparison here is between "UTF-8 without nameprep" and 
"ACE with nameprep."  This is like preferring fresh apples over rotten 
oranges; it has nothing to do with the relative merits of apples and oranges.

-Doug Ewell
 Fullerton, California