Punycode Mixed-case annotation

Wil Tan dready at gmail.com
Sun Jun 28 15:13:27 CEST 2009

Yes, that would work. Should we also discourage the use of such
labels, and explicitly say that XN-labels containing uppercase
characters are not A-labels?


On Sun, Jun 28, 2009 at 9:26 PM, Vint Cerf<vint at google.com> wrote:
> Wil,
> If we adopt a policy of mapping prior to look up, and if we map upper case
> to lower case,
> it may be that xn--RSUM-bpad.com will be changed to xn-rsum-bpad.com prior
> to lookup and it will work.
> vint
> On Jun 28, 2009, at 7:20 AM, Wil Tan wrote:
>> Hi folks,
>> RFC3492 contained a mixed-case annotation feature which, though not
>> used in IDNA2003, may affect the IDNA2008 specs. In particular, basic
>> code points ([a-z]) that are left unencoded in punycode may be
>> substituted in upper case, and the result of ToUnicode operation will
>> preserve them. For example,
>>  ToUnicode("xn--RSUM-bpad.com") = "RéSUMé.com"
>> From reading the rationale and protocol drafts, I'm not entirely sure
>> if the input is considered an A-label. The output is certainly not a
>> U-label since "RSUM" are disallowed codepoints.
>> I don't know if this is a problem, but it may warrant at least some
>> discussion in section 5.4 of idnabis-protocol?
>> =wil
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