Re: [idn] Zone rules (was: wg milestones update)

["Adam M. Costello" <amc@cs.berkeley.edu>]

Sun Guonian <sun@pier.cnnic.net.cn> wrote:

> for chinese user, the TC-SC equivalence rule is just alike the
> case-folding rule.

There are at least two differences.

First, case equivalence is much simpler.  It's almost always a
one-to-one map, and the few exceptions (like German sharp s)
disappear after you perform Unicode's "compatible decomposition"
(which is a one-to-many map).  As others have pointed out, the
traditional/simplified Chinese equivalence is much more complex.

This complexity is important because equivalence of domain names must
be computable by applications, not just DNS servers.  Browsers need to
check domain names for equality in order to do things like color visited
links and reject cookies from particular domains.

The second difference is that case equivalence is intuitive.  Any
person who knows the letter "a" also knows that "A" and "a" are the
same letter (even if you put diacritics on them, and even when they
appear in words of an unknown language).  I don't think this is true
of traditional/simplified Chinese characters.  If I'm not mistaken,
many people from China cannot read many of the traditional characters,
and many people from Taiwan, Hong Kong, etc. cannot read many of the
simplified characters.  And as others have pointed out, the equivalence
holds in Mandarin but not in Japanese (and I would guess not in
Cantonese and other Chinese languages, but I don't know).

AMC