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Re: bidi discussion list was: Bidi Markup vs Unicode control characters

From: Tex Texin <tex@xencraft.com>
Date: Wed, 10 Aug 2005 01:11:11 -0700
Message-ID: <42F9B69F.28421B62@xencraft.com>
To: Ognyan Kulev <ogi@fmi.uni-sofia.bg>
CC: Stephen Deach <sdeach@adobe.com>, Addison Phillips <addison.phillips@quest.com>, www-international@w3.org, Richard Ishida <ishida@w3.org>, Bert Bos <bert@w3.org>

I prefer nesting of xml elements to reflect the semantic relationship of
the elements.
That is not necessarily the same as the presentation relationships.

Also the relationship between runs is not always to embed (or pop) a
level. Sometimes there will be sibling relationships, which to maintain
presentation ordering will need some sequencing attributes. (All in all,
I think I prefer control codes for all of this. ;-) )

Of course, at some point you can assign a default value to each language
and use xml:lang, and insist the xml be created in the sequences and
nesting that cause it to display correctly on accessibility devices, but
in doing so, we would be writing visually rather than logically to some
extent, which is counter to design goals.

You might want to look at the bidi algorithm:
http://www.unicode.org/reports/tr9/

tex

Ognyan Kulev wrote:
> 
> Tex Texin wrote:
> > Ogi,
> > I think the short answer is no. "Direction" has a number of components
> > to it.
> > Instead of thinking of an instance of a single text string, consider a
> > series of text runs, with direction changes.
> 
> I admit that I'm haven't read much about bidi.  I just try to talk with
> common sense.
> 
> > When the language changes, does the direction level increase, is it
> > reduced, or is it a start of a new top-level direction setting? How does
> > each run relate to the surrounding runs? (In terms of the bidi
> > algorithm.)
> 
> XML elements already imply nesting of text runs.  Isn't that enough?
> 
> > Also, what is the layout direction, regardless of the language of each
> > text run?
> > For example, as you know in HTML, tables have a direction. Regardless of
> > the language of each cell's contents, the placement of the cell (or
> > column actually) is determined by the direction of the table.
> 
> <table> can use xml:lang too.
> 
> > Direction for a language can also be ambiguous. Chinese can be written
> > lr-tb, rl-tb, tb-rl...
> > (where l,r,t,b are left, right, top, bottom). The front page of some
> > Chinese newspapers can use all 3 of those directions/layouts.
> 
> When stylesheet is not used, you already give up on controlling layout
> and you choose to use some default layout for elements.  So isn't enough
> if one of these directions (lr-tb, ...) is chosen as default for
> language?  I don't know if this is acceptable for Chinese.
> 
> > So xml:lang might be suggestive, but it is not explicit or informative
> > enough to base bidi layout upon it alone.
> 
> My point is: isn't xml:lang enough for producing acceptable layout when
> there is no stylesheet?
> 
> Regards,
> ogi

-- 
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Tex Texin   cell: +1 781 789 1898   mailto:Tex@XenCraft.com
Xen Master                          http://www.i18nGuy.com
                         
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Received on Wednesday, 10 August 2005 08:11:30 GMT

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