Re: IdnaTest.txt and RFC 5893

From: Martin J. Dürst <>
Date: Wed, 4 Jan 2017 17:12:00 +0900

Hello Alastair,

On 2016/12/06 20:51, Alastair Houghton wrote:
> Hi all,
> I must be missing something; in IdnaTest.txt, in the BIDI TESTS section, there are examples like (line 74)

Can you tell us where you got IdnaTest.txt from?

> B; 0à.\u05D0; ; xn--0-sfa.xn--4db # 0à.א
> which the file alleges are valid, but I cannot for the life of me see why. First, “0à.א” is clearly a “Bidi domain name” since it has at least one RTL label, “א”. As such, the Bidi Rule (RFC 5893 section 2) should be applied to its labels, and the label “0à” fails [B1], since the first character has Bidi property EN, not L, R or AL.

On first sight, it looks to me as if you're correct.

For the exact interpretation of RFC 5893, you'd better write to the
mailing list of the former IDNA(bis) WG at

Regards, Martin.

> Similarly (line 93)
> B; àˇ.\u05D0; ; xn--0ca88g.xn--4db # àˇ.א
> Again, “àˇ.א” is clearly a “Bidi domain name”, but “àˇ” fails [B6], because “ˇ” has Bidi property ON, not L, EN or NSM.
> Have I misunderstood something fundamental here? Could someone explain why those examples are valid, in spite of RFC 5893?
> Kind regards,
> Alastair.
> --
> .

Prof. Martin J. Dürst
Department of Intelligent Information Technology
College of Science and Engineering
Aoyama Gakuin University
Fuchinobe 5-1-10, Chuo-ku, Sagamihara
252-5258 Japan
Received on Wed Jan 04 2017 - 02:12:47 CST

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