Greek Casefolding sigma

segred at segred at
Sat Mar 29 20:00:10 CET 2008

Dear Patrik,

What I ask is not to introduce a 25th character in our language (the  
final sigma as a new character).

The current status is: The final sigma is mapped to the small sigma.

Is the IDNA200X with the DISALLOWED form of final sigma still preserving this
mapping inside the protocol?

Kind Regards,

Vaggelis Segredakis

Quoting Patrik Fältström <patrik at>:

> On 28 mar 2008, at 18.52, Mark Davis wrote:
>> That would show
>> σωτήρης properly, and maintain compatibility.
> This is not about how to "show" things, as DNS is nothing else than a
> storage / lookup mechanism.
> You store a key, and together with that key some data. You can _NOT_
> send in the data and get the key back.
> The way IDNA2003 is designed is that the key does _NOT_ allow final
> sigma, and this because of design of Unicode. Regardless of if "the
> user typed" sigma or final sigma, the same key should match. Without
> changing the matching algorithm (that is out), the key have to be
> calculated on the client side. This key that is sent in is sigma, never
> final sigma.
> There is _no_ "reverse" mapping in DNS. Just lookup.
> That said, one can do a lookup of a PTR record where the data is a
> domain name. This domain name because of same rules as for the key can
> not include the sigma, but the final sigma. And if that is the problem
> people try to resolve, then that is what should be discussed, but that
> has not much to do with the creation of the key used in the lookup.
>    Patrik

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