Re: [idn] I-D ACTION:draft-ietf-idn-idna-08.txt

[Patrik Fältström <paf@cisco.com>]

--On 2002-06-09 17.47 -0500 "Eric A. Hall" <ehall@ehsco.com> wrote:

> on 6/9/2002 3:51 PM Adam M. Costello said the following:
> 
>> To say that a text string is
>> "case-sensitive" is to say that changing characters from upper to lower
>> case or vice-versa does change the identity of the string; in other
>> words, case differences are not ignored when the string is compared.
> 
> That's right.

Well, when working with Unicode, you need more specific text.

Two strings, X and Y, are said to be case insensitive if f(X) = f(Y) where
f() is either map to lower case or map to upper case. In nameprep we choose
to map to lower case. Further, we have added special mappings so f(f(X)) =
f(X).

Together with normalization this is a little bit tricker, and, because of
this complexity and given how DNS software work today, we chose to make the
mapping (nameprep) before the strings are used in DNS.

I.e. the heavy computation is when doing the mapping, and we optimize for
lookups, not storage. Lookup algorithm is exactly the same (given that the
input has passed ToASCII in IDNA of course).

   paf