Bidi tests on labels or domains?
simon at josefsson.org
Sun Jan 9 11:50:49 CET 2011
I need help with interpretation of this text in RFC 5891:
18.104.22.168. 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
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 22.214.171.124 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.
More information about the Idna-update