Bidi tests on labels or domains?
simon at josefsson.org
Sun Jan 9 16:24:33 CET 2011
Vint Cerf <vint at google.com> writes:
> all of the tests in IDNA2008 are oriented around labels, not around domain
> names. This means that each test applies, independently, to each label. The
> existence of an RTL label does not necessarily force any special testing on
> other labels in the domain name. If any particular label contains an RTL
> character (ie is take from an RTL-script), that label needs to be bidi
> the clue is here:
> If the proposed label contains any characters from scripts that are
> written from right to left, it MUST meet the Bidi criteria [RFC5893].
> since these are label by label tests (and not inter-label tests), only those
> labels that actually contain RTL characters need to be tested.
Thank you for clarification (again!) -- this is good as it simplifies
> On Sun, Jan 9, 2011 at 5:50 AM, Simon Josefsson <simon at josefsson.org> wrote:
>> I need help with interpretation of this text in RFC 5891:
>> 126.96.36.199. Labels Containing Characters Written Right to Left
>> If the proposed label contains any characters from scripts that are
>> written from right to left, it MUST meet the Bidi criteria [RFC5893].
>> The terminology used in RFC 5893 suggests to me that _all_ labels, not
>> just a RTL-label, in a bidi domain name needs to be tested:
>> Section 2 defines a rule, the "Bidi rule", which can be used on a
>> domain name label to check how safe it is to use in a domain name of
>> possibly mixed directionality.
>> A "Bidi domain name" is a domain name that contains at least one RTL
>> "RTL" and "LTR" are abbreviations for "right to left" and "left to
>> right", respectively.
>> An RTL label is a label that contains at least one character of type
>> R, AL, or AN.
>> The following rule, consisting of six conditions, applies to labels
>> in Bidi domain names.
>> I can't resolve my different readings. To my questions:
>> 1) Is the bidi rule in 188.8.131.52 intended to be invoked on a non-RTL label
>> if the domain name under testing is a bidi domain name?
>> 2) Is the same approach intended in section 5.4? It currently reads:
>> o Verification that the string is compliant with the requirements
>> for right-to-left characters specified in the Bidi document
>> The term "string" is used to refer both to labels and domains in
>> section 5, causing my confusion.
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>> Idna-update at alvestrand.no
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