Follow-up to Monday's discussion of digits
Alireza Saleh
saleh at nic.ir
Tue Nov 25 02:42:22 CET 2008
Hi,
I read the TR9 again, according to my understanding the only difference
between AN and EN will happen only if :
You have a RTL run(start the run with R) then having strong LTR
character(s) (L) ,followed by none or any Neutral character(s) and at
the end :
1) AN ES AN or
2) EN ES EN,
so the complete run would be like :
1) R L N AN ES AN or
2) R L N EN ES EN,
then you will see the difference between EN and AN. The numbers around
the ES will be displayed switched in case of AN or EN.
Please keep in mind that having both L and R in a label is prohibited by
IDNA bidi, also it is not possible to start the label with numbers
according to the current BIDI spec. therefore this difference doesn't
affect the IDN.
example 1)
تست.test.۴-۵
example 2)
تست.test.٤-٥
Finally I totally support any action to relax the IDNA so I support
removing the rule about mixing numbers in BIDI.
As I said earlier taking care of the visual confusions are registries
policy and responsibility, and it depends on the percentage of risk they
want to take. Some registries like it more secure some may like it more
relax.
Alireza
Kenneth Whistler wrote:
> Eric Brunner asked:
>
>
>> Could you point out where the "slightly different *directional*
>> behavior, with distinct bidi properties" is present? I'm reading TR9 but
>> I don't yet see where this matters. Examples of the differences would be
>> nice.
>>
>>
>
> Well, I'm not a bidi expert myself, so I'd appreciate it
> if anyone who has actually implemented this stuff could
> chime in here...
>
> But my reading of the bidi algorithm would concur that for
> *most* contexts, bc=AN versus bc=EN isn't going to make any
> difference in the final layout order of lines.
>
> The exception would seem to be in the following contexts:
>
> L N EN --> L N L --> L L L
> L N AN --> L N AN --> L e AN
>
> For L L L you are going to get resolved levels 0 0 0 in a L-to-R
> context and 2 2 2 in a R-to-L context. And everything in the
> stretch is going to display L-to-R in either.
>
> For L e AN you get resolved levels 0 0 2 in a L-to-R context
> and 2 1 2 in a R-to-L context. For that one, the neutrals
> in between the L and the AN make a significant difference then
> in the final layout result. You reverse both runs of 2's
> separately, and then the entire span including the neutrals.
> That gives you a very different outcome than if you had
> started with an L N EN sequence, instead.
>
> I could be wrong here, though -- so if somebody who knows better
> can correct me, that would be great. Also I'm not clear
> regarding what about the behavior of neutrals in the context
> of strong L strings and Perso-Arabic numbers versus Arabic
> numbers led the designers of the bidi algorithm in the first
> place to difurcate the properties to have this result.
>
> --Ken
>
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