Re: Inputting mixed SC/TC (Re: [idn] A question...)

["Adam M. Costello" <idn.amc+0@nicemice.net.RemoveThisWord>]

"D. J. Bernstein" <djb@cr.yp.to> wrote:

> ``Nobody has given a coherent explanation of _why_ IDNA needs to do
> certain mappings and not others,'' I wrote.
> 
> Patrik responded:
> > Because we do comparison of Unicode strings.
> > See http://www.unicode.org/unicode/faq/normalization.html
> > I.e. not our choice (more than choosing to use Unicode).
> 
> Patrik is lying.

Unlikely.  He probably just didn't understand your question exactly the
way you intended it.  Language isn't perfect, misunderstandings happen.

> The web page that he cites does _not_ require, or even suggest, that
> uppercase and lowercase should be considered equivalent.

Right.

The reason IDNA does case-folding is to be consistent with the existing
standard for domain names, which says they are case-insensitive.  Not
everyone considers that a sufficient reason, and we've been through
all the arguments on both sides, but that is the reason.  There are
many ways IDNA could have been designed differently and still work, and
this is one of them, but at the end of the day we need to use our best
collective judgement and make a choice.  There does not exist a solution
that everyone would agree is the best possible in all respects.

AMC