draft-klensin-idnabis-protocol-04 section 4.5

[Simon Josefsson]

The quoting was selective.  As far as I can see in the document,
registration also mention NFC (4.2), contextual rules (4.3.2.2), leading
combining marks (4.3.2.1).

/Simon

Vint Cerf <vint at google.com> writes:

> martin,
>
> this is an area where clarity will help so your assistance is
> appreciated.
>
> 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?
>
> v
>
>> This is irrelevant to the charter, but I have difficulties
>> understanding
>> 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:
>>>
>>> (registration)
>>>
>>> 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
>>> does
>>>   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
>>> part
>>>   of labels being processed for registration in the DNS.
>>>
>>> (lookup)
>>>
>>> 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
>>> for
>>>   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
>>>      [IDNA200X-Tables].
>>>
>>>   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
>>>      present.
>>>
>>>   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
>>> in
>>>      the table of rules.  With the exception in the rule immediately
>>>      above, applications resolving DNS names or carrying out
>>> equivalent
>>>      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:
>>> Note
>>>      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
>>>> josef゜on'
>>>> or 'dェtェkonsult'.
>>>>
>>>
>>> Read the drafts. It helps.
>>>
>>>                 Harald
>>>
>>>
>>> _______________________________________________
>>> Idna-update mailing list
>>> Idna-update at alvestrand.no
>>> http://www.alvestrand.no/mailman/listinfo/idna-update
>>
>>
>> #-#-#  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
>> http://www.alvestrand.no/mailman/listinfo/idna-update