Unicode 5.2 -> 6.0

Tina Dam tina.dam at icann.org
Thu Oct 14 22:22:10 CEST 2010

Hi Patrick, thanks for this. It was sooner than I expected...

In terms of the forward progress, I agree with your recommendation for the specific example. Generally I think in order to choose between the options (accept change or add exception for backward compatibility) I would personally like to hear from registries that have implemented the character and who may be disadvantaged by it's elimination.

For this specific case, I am personally unaware of any IDNs with the New Tai Lue script. However, we should probably make some sort of process where the gTLD registries and ccTLD registries are asked to provide relevant input if/when this happens again.

I have just suggested to the gTLD registries, and will make the same suggestion to the ccTLD registries, that we have a session in the upcoming meeting in Cartagena, Colombia, on the subject of the transition from the old IDNA and to the new revised version. It probably make sense to add this subject to the discussion and I'm happy to do so.


> -----Original Message-----
> From: idna-update-bounces at alvestrand.no [mailto:idna-update-
> bounces at alvestrand.no] On Behalf Of Patrik Fältström
> Sent: Wednesday, October 13, 2010 10:47 PM
> To: idna-update at alvestrand.no work
> Subject: Unicode 5.2 -> 6.0
> [This has also been sent to IAB]
> We will shortly see Unicode 6.0 released. This implies we will see a
> new list of derived property values be calculated based on the
> algorithm in RFC 5892.
> There are incompatible changes in three codepoints:
> 1. The following two that go to PVALID from DISALLOWED:
> This because they go from General Category So to Lo.
> 2. This moves from PVALID to DISALLOWED:
> It has changed GeneralCategory from Nd to No.
> In both cases the rule that create the difference is in section 2.1 of
> RFC 5892 LetterDigits(A):
> > 2.1.  LetterDigits (A)
> >
> >   A: General_Category(cp) is in {Ll, Lu, Lo, Nd, Lm, Mn, Mc}
> There are two alternatives for the IETF:
> A) Accept the change and stay aligned with Unicode
> The changes made are all "bugs" in the tables that are resolved. The
> most troublesome of the three codepoints would be U+19DA as that goes
> from PVALID to DISALLOWED, as that potentially would make domain names
> registered with that codepoint be invalid.
> B) Add these three as exceptions for backward compatibility.
> One can add the three (or subset thereof) to section 2.7 in an updated
> version of RFC 5892:
> > 2.7.  BackwardCompatible (G)
> >
> >    G: cp is in {}
> This set is in RFC 5892 empty, but characters can be added. Characters
> with explicit derived property value. This would require an IETF
> action.
> The wg after long discussions came to the rough consensus that IETF
> action should be needed for update of the backward compatibility list
> because we should be forced to discuss whether alternative (A) or (B)
> above should be used. At least the first couple of times. In a future
> RFC we could say that IANA is to hold a table with the backward
> compatibility list, and for example allow an appointed expert take care
> of the update of that list.
> I was personally in favour of needing an IETF discussion if/when we had
> this issue between Unicode versions. And here we are. I welcome the
> discussion.
> My personal suggestion is that if noone can show that domain names are
> in fact registered or used with U+19DA according to IDNA2008, IETF
> should accept the incompatible changes, and stay completely aligned
> with Unicode 6.0.
>    Patrik - liaison from IETF to Unicode Consortium
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