IdnaTest.txt and RFC 5893

Alastair Houghton alastair at
Tue Dec 6 05:51:55 CST 2016

Hi all,

I must be missing something; in IdnaTest.txt, in the BIDI TESTS section, there are examples like (line 74)

  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.

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,



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