draft-klensin-idnabis-protocol-04 section 4.5

[John C Klensin]

--On Friday, 28 March, 2008 06:42 -0400 Vint Cerf
<vint at google.com> wrote:

> 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?

Because MAYBE was removed in some haste, I did not carefully
review all of the relevant surrounding text when it was pulled
out.  Clearly, that review must be done and the text updated and
clarified.   I will do so as soon as we get the charter settled.
As usual suggestions about text from others would be welcome.

    john



>> 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
> 
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