Touchstones for "Mapping"

Vint Cerf vint at
Tue Mar 31 14:44:54 CEST 2009


for IDN-aware application, storage as A-labels has the benefit of  
storing an unambiguous string that can be converted directly to U- 
label form.

For IDN-unaware applications it isn't clear what will happen to a U- 
label (presented in some strange way maybe? IDN-unaware means the  
software thinks domain names are ASCII only) but at least the A-label  
form conforms to IDN-unaware domain name expectations.

So I am not sure I follow your line of reasoning.


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

On Mar 31, 2009, at 3:57 AM, Martin J. Dürst wrote:

> I very much agree with Harald. We are working on IDNs because we want
> humans to be able to easily read domain names in their script. Storing
> them as A-Labels when there is a reasonable chance that humans will
> have a look at them (e.g. in HTML or XML source, email source,...)
> is against the very intent of IDNs. Authors are humans, too, even
> if they work on plain text :-!
> Regards,    Martin.
> On 2009/03/30 15:32, Harald Tveit Alvestrand wrote:
>> Andrew Sullivan skrev:
>>> On Wed, Mar 25, 2009 at 09:08:36PM +0100, Harald Alvestrand wrote:
>>>> terminology quibble:
>>>> if it's an U-label, then it's already in canonical form....
>>> Yes, but my view still stands: it's way better to have the A-Label
>>> form, because you can't be sure that whatever looks at the U-Label
>>> later won't be an IDNA2003 client.
>> I agree with you for all cases where the "whatever looks at the  
>> label"
>> won't be a human with a text display who expects to find human  
>> readable
>> strings.
>> Among all the good things said about A-labels, "human readable" is  
>> not
>> one of them.
>>                   Harald
>> _______________________________________________
>> Idna-update mailing list
>> Idna-update at
> _______________________________________________
> Idna-update mailing list
> Idna-update at

More information about the Idna-update mailing list