referencing IDNA2008 (and IDNA2003?)

Mark Davis ☕ mark at
Sun Oct 24 19:55:10 CEST 2010

> These A-label having been initially registered as IDNA2003, IDNA2008 or
xn-ascii does not make any difference.

There is a bit of a problem in terminology. I used the term "punycode label"
to include labels of the form "xn--...", where the ... is valid Punycode
representations (in ASCII) of a Unicode string (with non-ASCII characters).

If we are speaking precisely, the term "A-Label" is defined in IDNA2008, and
is more restrictive. It does not include all the punycode labels that are
valid in IDNA2003. So "" (= http://€ does not have an A-Label in it, but is a punycode label,
and is valid in IDNA2003.

Because A-Label is defined in IDNA2008 (not in IDNA2003), we should follow
the IDNA2008 definition precisely. Otherwise communication becomes difficult
-- two people think they are in agreement about a point involving A-Labels,
when they mean different things, and are thus not in agreement.


*— Il meglio è l’inimico del bene —*

On Sat, Oct 23, 2010 at 19:05, jean-michel bernier de portzamparc <
jmabdp at> wrote:

> 2010/10/24 Mark Davis ☕ <mark at>
> I'm in agreement about the usefulness of storing the punycode form. As to
>> what you would like to see, Patrik, I'm in agreement there as well; that the
>> goal is IDNA2008. And I think we'll get there eventually, when the major
>> registries disallow the registrations of non-IDNA2008 names.
> Dear Mark,
> whatever the policy of the "registries", their transitions, their interest
> in Unicode, their commercial, cultural or political strategies, etc.  they
> only use A-labels as far as the Internet and the Internet DNS are concerned
> (them having "xn--" headers or not - remember that until IDNA2003 every
> cooky was A-label only). These A-label having been initially registered as
> IDNA2003, IDNA2008 or xn-ascii does not make any difference. Cookies are not
> interested in the origin of the domain name, but in the value of the domain
> names. Every IDN has one and only one lowercase A-label value. And this
> value is here to stay.
> Considering anything else for cookies, is to reintroduce the confusion that
> IDNA2008 clarified.
> Remember the sensible ".su" position: they will not register U-labels, but
> only A-label whatever the reverse punycodability.
> The problem for implementers is not there. The problem is to obtain a local
> user authoritative A-label, something the AD was told not to ask but IAB
> will have to document.
> Portzamparc
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