my comments on draft-ietf-idnabis-bidi-05

[John C Klensin]

--On Monday, September 07, 2009 6:21 PM +0900 "\"Martin J. 
Dürst\"" <duerst at it.aoyama.ac.jp> wrote:

> I herewith formally propose to:
>
> In 1.4, to make things easier to follow, change
> "o  BN - Boundary Neutral - control characters"
> to
> "o  BN - Boundary Neutral - control characters (in the context
> of this  document, ZWJ and ZWNJ)"

I'm fairly strongly opposed to this because it means that, if we 
make some other BN character context-dependent in the future, 
perhaps with respect to some newly-added script with other than 
left-to-right behavior, we have to change things in two places. 
Part of the current model, falling out from 
Unicode-version-independence, is that changes, even 
changes-by-exception, are very isolated.  Restricting BN in Bidi 
to ZWJ/ZWNJ would be a fairly  significant step and I haven't 
seen anything I'd consider a strong enough argument for doing 
it.  Just my opinion, of course.

> In 2., change point 5 from:
> "  5.  In an LTR label, only characters with the BIDI
> properties L, EN,         ES, CS.  ET, ON and NSM are allowed."
> to
> "  5.  In an LTR label, only characters with the BIDI
> properties L, EN,         ES, CS.  ET, ON, BN and NSM are
> allowed."

Maybe, but, if a change is really needed here, my instinct would 
be to say "only characters...ON, NSM, and characters 
specifically allowed by contextual rules, are allowed" or 
something to that effect.

best,
    john