Greek Casefolding sigma

Paul Hoffman phoffman at
Sat Mar 29 22:05:26 CET 2008

Let me make an attempt at this, since those of the previous posters 
didn't seem to work.

At 9:00 PM +0200 3/29/08, segred at wrote:
>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.

That is, in IDNA2003, a final sigma in an input string is mapped to a 
small sigma.

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

No, because there is no mapping inside the protocol. That seems to be 
unclear in the current protocol document 
(draft-klensin-idnabis-protocol-04.txt). However, the protocol does 
suggest, possibly too gently, that the application that takes the 
user's input might do mapping itself, outside the protocol:

5.3.  Character Changes in Preprocessing or the User Interface

    The Unicode string MAY then be processed, in a way specific to the
    local environment, to make the result of the IDNA processing match
    user expectations.  For instance, at this step, it would be
    reasonable to convert all upper case characters to lower case, if
    this makes sense in the user's environment.

An interface that understands that a final sigma should be mapped to 
a small sigma would do that in this step.

More information about the Idna-update mailing list