Mapping and Variants

Martin Duerst duerst at
Sat Mar 7 09:07:05 CET 2009

At 03:27 09/03/07, Andrew Sullivan wrote:
>On Fri, Mar 06, 2009 at 12:13:35PM -0500, John C Klensin wrote:
>> Well... A different way to look at this is that you can have all
>> of the case sensitivity, case-independent matching, and case
>> preservation you like in A-labels (as well as all other labels
>> that contain ASCII characters and maybe some others).  IDNA does
>> not change the DNS.
>> A different way to state Erik's observation/suggestion would be
>> that, in IDNA-aware "slots" use (on registration, lookup,
>> storage in files, etc.) of anything but lower case needs to be
>> really strongly discouraged.   That would imply that, in a given
>> "slot", the decision that IDNA can be used is a decision that
>> upper case is discouraged and violence may be done to it if it
>> appears.  That is an application-layer design tradeoff, not a
>> statement about the DNS or a problem for 1034.
>Actually, putting something like those two paragraphs together might
>make this idea rather more palatable.

Although the wording might turn out quite differently, and not
restricted to lower case, that's more or less what I planned
to do in the IRI spec: Make sure you use whatever the 'resolver'
(here used in a sense wider than just the DNS) considers the
'canonical' variant, or you risk that there will be resolution

Regards,    Martin.

#-#-#  Martin J. Du"rst, Assoc. Professor, Aoyama Gakuin University
#-#-#       mailto:duerst at     

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