Touchstones for "Mapping"

Vint Cerf vint at
Wed Mar 25 00:25:24 CET 2009

I think the symmetry of A-label and U-label together with the use of  
only U+002E for separator would allow either or both to be stored. The  
A-label has the peculiar advantage that it signals that it is an IDN  
with "xn--" and, of course, can be used directly for lookup as well as  
being convertible to U-label form at need.


Vint Cerf
1818 Library Street, Suite 400
Reston, VA 20190
vint at

On Mar 24, 2009, at 7:16 PM, Andrew Sullivan wrote:

> On Tue, Mar 24, 2009 at 03:46:01PM -0700, Lisa Dusseault wrote:
>> 1.  Canonical forms:  encourage labels to be stored and displayed,
>> whenever possible, in a canonical form.  The protocol only uses the
>> canonical form.
> Is that "labels" or "U-Labels"?  (I was going to ask this clarifying
> question at the mic, but we were running out of time).  My own opinion
> is that much of the time, if you have to store something, it would be
> better to store the A-Label, becuase then you can be sure you could
> actually resolve the same owner name if you had to do it again.  The
> symmetry in IDNA2008 is a help in this case: it lets you do that and
> get back "what the user typed".
> A
> -- 
> Andrew Sullivan
> ajs at
> Shinkuro, Inc.
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