[precis] PRECIS bidi rule for usernames

William Fisher <william.w.fisher@gmail.com> Fri, 07 October 2016 19:00 UTC

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From: William Fisher <william.w.fisher@gmail.com>
Date: Fri, 7 Oct 2016 12:00:31 -0700
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Subject: [precis] PRECIS bidi rule for usernames
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I've been working on a python implementation of the PRECIS specification
(https:github.com/byllyfish/precis-i18n).

The Username profiles apply the "bidi rule".

       Directionality Rule: Applications MUST apply the "Bidi Rule"
       defined in [RFC5893] to strings that contain right-to-left
       characters (i.e., each of the six conditions of the Bidi Rule
       must be satisfied).

Can someone please clarify whether:

A. The "Bidi rule" is ONLY applied to strings that contain right-to-left
characters.
B. The "Bidi rule" is applied to ALL strings.

If the answer is A, then "Juliet+" is a valid username.

If the answer is B, "Juliet+" is not a valid username because it violates
the Bidi rule.

I think the answer is probably A. However, this implies that right-to-left
usernames can never begin or end with ASCII punctuation.

Thanks,
Bill