Re: Bidi issues

Roy Badami <[email protected]> wrote:

> The problem with [applying the Stringprep bidi check to individual
> segments rather than to the entire local part] is that although it
> allows mixed LTR/RTL labels, it results in much stronger restrictions
> on RTL labels, since each RTL segment must now begin and end with an
> RTL character.  As previously discussed, A1-2B becomes illegal, for no
> obviously good reason, if we choose to segment on hyphen (all examples
> in logical order unless otherwise indicated).
>
> More significantly, I think, any approach based on the current
> stringprep restrictions prevents an RTL localpart from ending with
> digits.  With existing (ASCII) localparts, it is common practice
> to a append a number to the user's name or initials in order to
> disambiguate users with the same initials or names.  The address
> [email protected] is completely unambiguous, but would be disallowed by any
> bidi restrictions based on stringprep, for no evidently good reason.

This is all true, but how much of a burden would it be?  Would Arabic
local parts even want to use the European digits?  The middle-eastern
scripts chapter of the Unicode standard suggests that languages that use
Arabic scripts usually prefer the Arabic-Indic or Extended Arabic-Indic
digits, which would be allowed at the end of a local part.  Maybe the
final-digit problem would in practice only be a problem for Hebrew.
That would be a drastically smaller affected population (by a factor of
around 40 I think).

> I was proposing that there be no bidi restrictions at all on the
> localpart (ie use a variant of nameprep without the stringprep bidi
> restrictions).

That's an interesting idea that I hadn't considered.  It would be a
departure from the architecture envisioned in the IRI draft (which was
apparently the architecture in the minds of the people who provided the
bidi check in Stringprep), but it would be a simple way to achieve our
goal of allowing owner-RTL.  The main question is, if the bidi check
were applied to individual segments, would it do more harm than good, or
more good than harm?  It's not obvious to me.  We could use some more
opinions.

> http://www.gnomon.org.uk/bidi-ambiguities.txt

I haven't looked at it yet, but I will.  Thanks!

AMC