idna-mapping update

Vint Cerf vint at
Tue Dec 22 03:01:25 CET 2009


So perhaps the sensible thing is to engage on the question
of mappings that seem to make sense on an ongoing basis
and those that really ought to end at some point (examples of
these would be sharp-s and final sigma)?

could that be a part of the effort proposed by Cary Karp?


On Dec 21, 2009, at 8:55 PM, Kenneth Whistler wrote:

> Vint,
>> the mappings document was deliberately not normative. It outlined a
>> set of mappings that the authors and others saw as meeting user
>> expectations created in part by the case insensitivity of the ASCII
>> DNS, for example. It does not promote the more extensive mapping  
>> found
>> in TR46. Despite the backward compatibility arguments, at least some
>> of us worry that the TR46 mappings may tend to create defacto  
>> behaviors in IDN domain name labels by characters that aren't, in  
>> fact
> But that is *already* the case for every uppercase Latin, Greek,
> and Cyrillic letter in Unicode. Those are all *DISALLOWED* in
> the tables document in IDNA 2008. And the whole point of
> talking about case insensitivity in the mapping document and
> suggesting that mapping to lowercase might be an interesting
> thing to do before resolving by IDNA 2008 is to treat them
> as if they were defacto "PVALID" in IDN domain name labels.
> Because that is what everybody expects, and it would be
> crazy not to.
> The same thing applies to the width variants already discussed
> in the mappings document, except that those are compatibility
> width variants, rather than case pairs. And once again, they
> are *DISALLOWED* by the protocol, but mapping them as suggested
> in the mappings document creates defacto "PVALID" behaviors
> in IDN domain name labels for them.
> So the only way I can interpret what you are saying here is that
> somehow the group that produced the mappings document seems to
> think that there are some "good" mappings (for case pairs
> and width variants) that are suggested to produce defacto
> "PVALID" behaviors, and there are other "bad" mappings from
> IDNA 2003 that shouldn't. But it isn't explicit enough about
> that distinction, and in any case I don't think there was
> ever really consensus about that point. Instead, there was
> just a general weariness and a sense that if the document
> wasn't normative, who cares what the recommendation in it
> was, so why fight about it?
>> At least that's how I have been interpreting the distinction.
>> They also create a kind of conflict with the canonical A-Label/U- 
>> label
>> commutation of IDN2008.
> How does having a recommendation to do half of the mappings
> like IDNA 2003 and not do the other half of the mappings
> like IDNA 2003 not also create that conflict?
> The way I interpret Michel's suggestion is that *if* the
> mapping document is going to make any suggestions at all
> about what might be useful things to map before resolving
> an input string by the IDNA 2008 protocol, then it is
> way better to make that suggestion be precise and as close
> to compatibility with IDNA 2003 as possible, since that
> is quite likely what all the major browser implementers
> will do anyway.
> Otherwise, just junk the whole suggestion section in the
> mapping document and wave over at TR46 for a suggestion
> instead.
> I'd be fine with either approach. But a halfway approach
> that is vague about what mappings might be useful, based
> on some notion that this is what end users might expect
> is less than helpful. What matters here is what the
> implementers of the IDNA libraries and the browsers and
> indexers expect about backwards compatibility with
> IDNA 2003 mappings, IMO.
> --Ken

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