Greek Casefolding sigma

Mark Davis mark.davis at
Fri Mar 28 18:52:36 CET 2008

I think a better solution to this problem is to have a post-processing step
for display, where the lowercase sigma is mapped to a final form according
to the rules in Ch. 3 of the Unicode Standard. That would show
σωτήρης properly, and maintain compatibility. The only case where
something extra needs to be done is when a label has multiple words --
people would need to have a hyphen in labels after final sigmas. That is,
you'd see σωτήρης-σωτήρης if the hyphen is used, instead of
σωτήρησσωτήρης if it weren't.


(There are messages with more background on why for comparison both Σ and ς
are converted to σ in the archives; it's also discussed in the Unicode
Standard, see

On Fri, Mar 28, 2008 at 10:11 AM, Patrik Fältström <patrik at>

> On 28 mar 2008, at 17.51, John C Klensin wrote:
> > I personally believe that you have adequately
> > explained the "correct and appropriate" part in your two notes
> > and earlier materials posted to the list, but others may have
> > different opinions on that subject.   For the second, it would
> > be useful to know exactly what your registries, and any other
> > registries that might have registered labels in Greek, propose
> > to do to deal with differences between the IDNA2003 behavior
> > (map to lower-case medial sigma) and your proposed IDNA200X
> > behavior (treat final sigma as a normal character).
> FWIW, I completely agree with this. I personally think you have
> explained why you need the codepoint. What you have to explain is how
> incompatibility issues with IDNA2003 are dealt with.
> To be very explicit, the codepoint 0x03C2 was not possible to register
> according to IDNA2003 as it was mapped to 03C3, so it was DISALLOWED
> in IDNA2003, and also DISALLOWED in IDNA200X.
>    Patrik
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