draft-klensin-idnabis-protocol-04 section 4.5
simon at josefsson.org
Fri Mar 28 12:03:18 CET 2008
The quoting was selective. As far as I can see in the document,
registration also mention NFC (4.2), contextual rules (126.96.36.199), leading
combining marks (188.8.131.52).
Vint Cerf <vint at google.com> writes:
> this is an area where clarity will help so your assistance is
> John Klensin,
> on the surface, I can see Martin's point. Is there additional language
> in "rationale" that might clear up this uncertainty? Or perhaps more
> needs to be said?
>> This is irrelevant to the charter, but I have difficulties
>> from the citations below how registration is stricter than lookup.
>> Registration only mentions DISALLOWED and UNASSIGNED, whereas
>> lookup mentions NFC, contextual rules, and combining marks in
>> first position on top of that. So I get the impression that
>> lookup is more restricted that registration. What did I get wrong?
>> Regards, Martin.
>> At 21:37 08/03/27, Harald Alvestrand wrote:
>>> From draft-klensin-idnabis-protocol-04:
>>> 4.3. Permitted Character and Label Validation
>>> 4.3.1. Rejection of Characters that are not Permitted
>>> The Unicode string is examined to prohibit characters that IDNA
>>> not permit in input. Those characters are identified in the
>>> "DISALLOWED" and "UNASSIGNED" lists that are discussed in
>>> [IDNA200X-Rationale]. The normative rules for producing that list
>>> and the initial version of it are specified in [IDNA200X-Tables].
>>> Characters that are either DISALLOWED or UNASSIGNED MUST NOT be
>>> of labels being processed for registration in the DNS.
>>> 5.4. Validation and Character List Testing
>>> In parallel with the registration procedure, the Unicode string is
>>> checked to verify that all characters that appear in it are valid
>>> IDNA resolution input. As discussed in [IDNA200X-Rationale], the
>>> resolution check is more liberal than that of the registration one.
>>> Putative labels with any of the following characteristics MUST BE
>>> rejected prior to DNS lookup:
>>> o Labels containing code points that are unassigned in the version
>>> of Unicode being used by the application, i.e., in the
>>> "Unassigned" Unicode category or the UNASSIGNED category of
>>> o Labels that are not in NFC form.
>>> o Labels containing prohibited code points, i.e., those that are
>>> assigned to the "DISALLOWED" category in the permitted character
>>> table [IDNA200X-Tables].
>>> o Labels containing code points that are shown in the permitted
>>> character table as requiring a contextual rule and that are
>>> flagged as requiring exceptional special processing on lookup
>>> ("CONTEXTJ" in the Tables) MUST conform to the rule, which
>>> MUST be
>>> o Labels containing other code points that are shown in the
>>> permitted character table as requiring a contextual rule
>>> ("CONTEXTO" in the tables), but for which no such rule appears
>>> the table of rules. With the exception in the rule immediately
>>> above, applications resolving DNS names or carrying out
>>> operations are not required to test contextual rules, only to
>>> verify that a rule exists.
>>> o Labels whose first character is a combining mark. [[anchor15:
>>> in Draft: this definition may need to be further tightened.]]
>>> .... more text follows .....
>>>> What I'm trying to understand is what an IDNA200x implementation
>>>> will do
>>>> (i.e., which output string or what error) when the user types
>>>> or 'dェtェkonsult'.
>>> Read the drafts. It helps.
>>> Idna-update mailing list
>>> Idna-update at alvestrand.no
>> #-#-# Martin J. Du"rst, Assoc. Professor, Aoyama Gakuin University
>> #-#-# http://www.sw.it.aoyama.ac.jp
>> mailto:duerst at it.aoyama.ac.jp
>> Idna-update mailing list
>> Idna-update at alvestrand.no
More information about the Idna-update