The Two Lookups Approach (was Re: Parsing the issuesand finding a middle ground -- another attempt)

Patrik Fältström patrik at
Sat Mar 7 19:33:32 CET 2009

On 7 mar 2009, at 18.13, Erik van der Poel wrote:

> I think I agree with you, but I also think the wording you chose today
> can easily be misunderstood.
> IDNA2003 is absolutely clear about "what goes in DNS", i.e. Punycode
> with xn-- prepended. In fact, it was careful to specify that /all/
> IDNA-unaware domain name slots must receive that format (xn-- with
> Punycode).

Ok, you are absolutely correct of course.


My intention was to say, which I know you understand, was that when  
using IDNA2003, people are confused over what unicode characters are  
mapped to other unicode characters and then to punycode format, and  
what unicode characters can be turned into punycode directly.


> The term "U-label" is indeed one of the good things about IDNA2008.
> This makes it very easy for other specs (e.g. SMTP-related) to specify
> the use of U-labels. If those specs had to use IDNA2003 terminology,
> it would sound a bit clunkier e.g. "only strings that would be
> generated by first applying ToASCII, then ToUnicode".
> So I still believe that removing mappings from IDNA is a good thing,
> because it allows the higher layers (such as the series of SMTP specs)
> to avoid the mess that HTML got itself into. If there are no mappings
> in the base IDNA2008 spec, the SMTP spec can refer directly to that
> base spec, and avoid the issues surrounding Eszett et al.
> This does not mean that a mapping spec is unnecessary. Far from it. In
> order to maximize interoperability in situations where the original
> typist's language is unknown, we must have a crystal clear global
> mapping spec, i.e. language-independent.
> This does not mean that a local (language-specific) mapping
> recommendation is unnecessary. Far from it. In order to maximize
> interoperability in the keyboard UI and registrar UI contexts, we must
> provide crystal clear recommendations about the types of local
> mappings that are reasonable and those that are not.
> I believe the HTML IDNA mess could be cleaned up somewhat by making
> the HTML implementations stricter, e.g. by requiring U-labels or even
> A-labels. It would be a complete disaster if HTML implementers went in
> the other direction, i.e. more lenient, by performing
> language-specific mappings on domain names in hrefs. I hope many would
> join me in publicly and strongly criticizing any HTML implementer that
> makes such a mistake.
> Please, please, no more mistakes in HTML implementations.
> Erik
> On Sat, Mar 7, 2009 at 6:24 AM, Patrik Fältström <patrik at>  
> wrote:
>> Regardless of in what direction this is going, I want personally  
>> this to
>> very clearly be something that is done "before" what we have in  
>> IDNA2008 is
>> used. So that what we really talk about is a standardized mapping  
>> procedure
>> that applications use. I do not want to see an extension of U- 
>> label. That we
>> have this definition now is one of the best things with IDNA2008,  
>> as we have
>> severe confusion with IDNA2003 where there is basically no difference
>> between what is mapped and what goes in DNS.
>> Because of this, I do not have so much interest personally in  
>> exactly what
>> is defined for this mapping, but I must say I am seriously confused  
>> by the
>> ideas on doing two lookups. I strongly support the list of issues  
>> Marcos
>> wrote about. You can _NOT_ do two lookups and think they have any  
>> context
>> between them what so ever.
>> I also want to remind people that we have had file systems with  
>> different
>> casing, line break and other special rules, and the world seems to  
>> have
>> survived...
>> I think we "just" need documents that talk about how to handle  
>> different
>> situations in the time of lookup (and similar recommendations for
>> registries, but registries have already worked with these issues  
>> for many
>> years, so I do not really see the big problem).
>>   Patrik
>> _______________________________________________
>> Idna-update mailing list
>> Idna-update at

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