Re: [idn] SC/TC equivalence

["Soobok Lee" <lsb@postel.co.kr>]

----- Original Message -----
From: "Adam M. Costello" <amc@cs.berkeley.edu>

> liana.ydisg@juno.com wrote:
>
> > [nameprep] is the place for case folding for Latin, then it should be
> > the place for other script folding as well.
>
> That's a valid argument, but there are also some counter-arguments:
>
> Existing domain names are already case-insensitive, so IDNs ought to
> be case-insensitive for consistency with the current standard.  This
> consistency constraint does not apply to SC/TC equivalence.
>

This is a really controversial issue.

NAMEPREP also applies additional equivalence rules in addition to
case-folding:
   1) compatibility decomposition
   2) canonical composition

What is the difference between these equivalences and SC/TC equivalence?


> With very few exceptions, case mapping is one-to-one.  SC/TC mapping is
> more complex more often.
>
> The case mapping rules are already defined in the Unicode standard.
> This is not true for SC/TC mapping.
>
The Unicord Standard is not the only document we can refer to.
I have no doubt about the accuracy of CNNIC-provided SC/TC mapping tables.


> Some people have expressed a desire to be able to register the
> simplified and traditional versions of a name as separate domain names
> No one has expressed an analogous desire to be able to register the
> all-uppercase and all-lowercase versions of a name as separate domain
> names.
>

If  SC/TC equivalence is like the equivalence between  "humor" and "humour",
registration/dispute resolution policy may be the right path to solve this
issue.

But, if SC/TC equivalence is like the equivalence between "H" and "h",
we should fold them. BTW, in which direction ?    SC->TC or TC->SC?
How can we recover the pre-normalization form of folded TC/SC domains?


--LSB