Unicode position on local mapping

John C Klensin klensin at jck.com
Wed Feb 18 01:10:24 CET 2009



--On Tuesday, February 17, 2009 14:38 -0500 Andrew Sullivan
<ajs at shinkuro.com> wrote:

> On Tue, Feb 17, 2009 at 12:40:38PM -0500, John C Klensin wrote:
> 
>> As one example of that, I've recently concluded that there is
>> no excuse for any mapping (local or otherwise) on the
>> registration side.  
> 
> To be clear, are you here distinguishing the narrow meaning of
> "mapping" to mean "transforming one character into another",

yes

> and another possible meaning, which is "expanding to match
> other characters, and registering those _too_?  For instance
> the example that Jefsey provided is just école.fr and
> ecole.fr, which could easily be resolved by registering
> ecole.fr also whenever xn--cole-9oa.fr is registered.  This
> doesn't need anything at all in the IDNA protocol -- you can
> do it all with registration bundling.

Exactly.  But I read Jefsey's note as saying that it was up to
the registry whether to do that or not.  If it was not done,
then the two strings would effectively be treated as completely
different strings, as different as, say, "école" and "school".
I agree with that, but note that, were the protocol to
do/require the mapping between "é" and "e", the registry would
be deprived of the ability to make the choice.   Of course, no
one has seriously suggested that mapping, but no one has
seriously suggesting mapping a-acute and a-grave together either.

     john





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