[idn] case preservation

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

----- Original Message ----- 
From: "D. J. Bernstein" <djb@cr.yp.to>
To: <idn@ops.ietf.org>
Sent: Tuesday, October 09, 2001 9:48 AM
Subject: Re: [idn] WG Update


> Suppose we deploy uppercase IDNs. This could turn out to be a mistake---
> in fact, a complete disaster---because uppercase Alpha looks just like
> uppercase A. We won't be able to fix the mistake, because people will
> already be relying on domain names that contain Alpha.

Greek small 'o' and Cyrillic small 'B' have the same looks with their
latin counterparts. This does not lead us to ban both of them.
It makes sense to map greek 'o' into latin 'o', but prohibiting greek 'o'
does not make sense. we have no standard yet on such look-alike mappings.

Desirable case preservation feature in ACE  is :

  to encode  Greek capital 'A'  as Greek small 'a' with 
     a case flag for 'Capital'.

  For example, AMC-ACE-Z encodes greek <alpha><epsilon><kappa>,
  
  all capital : U+03B1 U+03B5 U+03BA:  mxAIP 
  all small   : u+03B1 u+03B5 u+03BA:  mxaip

  Two output ACE labels are case-insensitively equivalent.

> 
> Suppose, on the other hand, we initially prohibit uppercase IDNs. If
> this turns out to be a mistake, we can fix it later, adding support for
> uppercase IDNs, without breaking anything.
> 

someone sticking to un-fixed old applications would lose.


> Dan Oscarsson writes:
> > If we are not going to support case-insensivity and case preserving in
> > responses, then we should turn it of for ASCII too.
> 
> Deprecating uppercase ASCII is fine. Of course, caches and servers will
> have to continue accepting uppercase ASCII for compatibility, but users
> shouldn't type any new names in uppercase.

The case information carries valuable preferred formating of a label:
 for example,  UN.org, WHO.org are much easier to recogize.
That's one of the reasons why Most browers and email clients preserve the case informations.

Soobok

> 
> > It *is* a requirement that case-insensitivity shall work for all letters.
> > That has been the DNS standard so far. That is what people expect.
> 
> ``It *is* a requirement that host names shall be ASCII. That has been
> the standard so far. That is what people expect.'' Stupid argument.
> 
> ---Dan
>