Comments on IDNA Bidi

John C Klensin klensin at
Fri Jan 18 00:42:00 CET 2008

--On Thursday, 17 January, 2008 18:31 +0100 JFCM
<jefsey at> wrote:

> At 15:54 17/01/2008, John C Klensin wrote:
>> The short answer is that it is not realistic, in the general
>> case,  to impose restrictions on one label based on the
>> contents of another.
> Except if you use classes triggered by an included code.
> This would not be backward compatible with current DNS (what
> would protect from confusion), but in the case of an IDN class
> it could be OK  fo a bidi additional class.


You are wasting your time and ours.  If you want to pursue an
entirely different approach, as one of your earlier notes
indicated that you intended to do, by all means do so.  But, if
you are going to make suggestions here, please familiarize
yourself sufficiently with the DNS that they are plausible.

Even with an alternate class approach, which is definitely not
on the table at the moment, one cannot, in general, tied the
interpretation of, or matching rules for, one label to the
content of another.   Independent of whether they might be of
any use in dealing with IDNs, DNS Classes are very well defined
and neither "included code" nor inter-label dependencies fit
into that definition.  

Some of the folks who are interested in "language domains" keep
making the error of believing this as well.  While one could
imagine policies that would keep an entire domain tree
homogeneous with respect to language, they would still not be
able to affect the interpretation of those labels (in addition
to being very difficult to enforce).


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