[gtld-tech] IDN Tables

[Kim Davies]

Hi John,

On Oct 22, 2013, at 4:49 AM, John Hollifield <John.Hollifield at nominet.org.uk<mailto:John.Hollifield at nominet.org.uk>> wrote:

I am a bit confused about how our IDN table should be structured with respect to variants as I feel section 5, A Model Table Format, of RFC 4290 (https://www.ietf.org/rfc/rfc4290.txt) is a bit ambiguous. I am therefore hoping there is somebody out there with experience of these things that could help me. I have looked at other IDN tables but none seem to help me with the issue below. The RFC states:
...
So if I have the following characters which are equivalent within the registry
e (U+0065) = è (U+00E8) = é (U+00E9) = ê (U+00EA) = ë (U+00EB)
...
U+0065|U+00E8:U+00E9:U+00EA:U+00EB # LATIN SMALL LETTER E (e)
U+00E8|U+0065:U+00E9:U+00EA:U+00EB # LATIN SMALL LETTER E WITH GRAVE
U+00E9|U+0065:U+00E8:U+00EA:U+00EB # LATIN SMALL LETTER E WITH ACUTE
U+00EA|U+0065:U+00E8:U+00E9:U+00EB # LATIN SMALL LETTER E WITH CIRCUMFLEX
U+00EB|U+0065:U+00E8:U+00E9:U+00EA # LATIN SMALL LETTER E WITH DIAERESIS

If the second method is the correct way does the order then become important?

I believe explicitly listing them out, your second method, is more desirable to ensure a naïve implementor gets it right. While some registries do enforce symmetry in their tables, I don't think it can be assumed. As for ordering, I don't think ordering is material within a set of variants.

This is probably a good point to raise awareness on work I and others have been doing on producing an improved table format which caters for more complex rulesets. You can find the current draft at http://tools.ietf.org/html/draft-davies-idntables-04. Our goal is to see this become a common format that all existing tables could be ported to. It will be used for the root zone label generation ruleset (i.e. the IDN table that governs variants in the root zone)

kim


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