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Re: Special ordering for BIDI URLs

From: Martin J. Dürst <duerst@it.aoyama.ac.jp>
Date: Tue, 25 May 2010 20:30:08 +0900
Message-ID: <4BFBB4C0.8060608@it.aoyama.ac.jp>
To: Slim Amamou <slim@alixsys.com>
CC: Mark Davis ☕ <mark@macchiato.com>, public-iri@w3.org, bidi@unicode.org, Shawn Steele <Shawn.Steele@microsoft.com>, Murray Sargent <murrays@exchange.microsoft.com>, aharon@google.com


On 2010/05/25 19:30, Slim Amamou wrote:
> 2010/5/25 "Martin J. Dürst"<duerst@it.aoyama.ac.jp>

>> Could you give a pointer to that 'proof'?
>
>
> http://www.alvestrand.no/pipermail/idna-update/2010-February/006528.html

I think that proof is wrong. Let's look at it in detail.

 >> (...)
 >> Label Uniqueness: No two labels, when presented in display order
 >>      in the same paragraph, should have the same sequence of characters
 >>      without also having the same sequence of characters in network
 >>      order, both when the paragraph has LTR direction and when the
 >>      paragraph has RTL direction.
 >
 >let ABC 3 different labels in network order A != B !=C
 >let JKL their LTR display order J != K != L
 >let MNO their RTL display order M != N != O
 >
 >given the requirement above :
 >
 >J = M           J = M = A
 >and       =>
 >K = N           K = N = B           JKL = ABC

I think that you say that because (J = M and K = N), it follows that
(J = M = A and K = N = B). I think this is wrong. The problem seems to 
come from assuming that "the paragraph has LTR direction" means that the 
labels will be arranged LTR. This is not the case if there are two or 
three adjacent RTL labels. In the specific case of three RTL labels 
(labels with only RTL characters), you will have (J = M = C and K = N = 
B and L = O = C).

Regards,   Martin.


 >                                     =>
 >K = N           K = N = B           MNO = ABC
 >and       =>
 >L = O           L = O = C
 >
 >                            L = N => L = K which is absurd
 >suppose L != O =>  or
 >                            L = M => L = J which is absurd
 >
 >
 >Note that this is a recursive demonstration : I demonstrated for N+1
 >labels which means that a domain name with any number of labels must
 >be displayed in network order to satisfy the requirement.



-- 
#-# Martin J. Dürst, Professor, Aoyama Gakuin University
#-# http://www.sw.it.aoyama.ac.jp   mailto:duerst@it.aoyama.ac.jp
Received on Tuesday, 25 May 2010 11:30:58 GMT

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