Tonus (was: Re: Casefolding Sigma (was: Re: IDNAbis Preprocessing Draft))

Patrik Fältström patrik at
Thu Jan 31 12:26:49 CET 2008

On 31 jan 2008, at 10.55, Vaggelis Segredakis wrote:

> Should I start spelling my name as Βαγγέλησ instead of  
> Βαγγέλης which is the
> correct spelling because some people had problems designing a  
> multilingual
> protocol for computers?

The Unicode Consortium has decided that at time of matching, there is  
an equivalence between the codepoints U+03C2 (GREEK SMALL LETTER FINAL  
SIGMA) and U+03C3 (GREEK SMALL LETTER SIGMA). This implies only one of  
these codepoints can be stored in the DNS. Further, the casefolding  
algorithm provided together with normalization state U+03C3 is the  
stable codepoint of the two, and because of that U+03C2 can not be  
stored in the core of a database for matchings.

The way IDNA2003 is designed, both U+03C2 and U+03C3 are mapped to U 
+03C3, which implies either of the two codepoints will match with U 
+03C3 that is stored in the DNS. And, because of this, you can  
according to IDNA2003 include U+03C2 in a domain name that you ask  
people to use (although U+03C3 is stored in the DNS).

IDNA200x is, for exactly the reasons this discussion exists --  
confusion, only talking about what can be stored in the DNS, and that  
is U+03C3 in both IDNA2003 and IDNA200x, all according to the design  
of the Unicode Character Set.

So, your issues have nothing to do with IDN and implementation of IDN,  
but design of the Unicode Character Set and I because of that ask you  
to direct your issues to the Unicode Consortium.


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