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Re: authoring @lang and @dir (was 3.6. The root element)

From: Robert Burns <rob@robburns.com>
Date: Thu, 2 Aug 2007 02:56:22 -0500
Message-Id: <EE34848A-3406-4B96-A145-3C72C5339815@robburns.com>
Cc: Sander Tekelenburg <st@isoc.nl>, public-html@w3.org
To: Maciej Stachowiak <mjs@apple.com>


On Aug 2, 2007, at 2:21 AM, Maciej Stachowiak wrote:

>
>
> On Aug 1, 2007, at 8:53 PM, Robert Burns wrote:
>
>>
>> I'm not really sure what you're asking. But what I'm trying to say  
>> is that fully expressing a language using @lang or @xml:lang  
>> provides all of the information required to deduce the  
>> directionality. So to take just one of the examples I gave above:
>>
>> lang='iw-LATN'=> dir='LTR'
>>
>> In that case the @dir attribute is technically redundant. I'm not  
>> saying that UAs work that way now. Rather I'm saying that by  
>> specifying language (including the specification of unconventional  
>> scripts), all the information is there to determine  
>> directionality. For some languages what demarcates the  
>> unconventional script may be up for debate and can even be a  
>> political football. If the web was around a century ago or so when  
>> Turkey was imposing a change from Arabic to Latin script, it would  
>> be difficult to say which was the conventional script. It would  
>> probably require specifying precisely which one was in use either  
>> way (if the government permits it).
>>
>> Again, though having @dir as a separate attribute saves UAs from  
>> the need to process language codes to determine directionality. It  
>> also is more flexible in the sense that an author can specify only  
>> @dir and leave @lang unspecified. Or specify @dir and @lang but  
>> provide only the primary language code with no script code. Doe  
>> that answer your question?
>
> HTML4 says that "User agents must not use the lang attribute to  
> determine text directionality", and current user agents respect  
> this. It is highly likely that content depends on lang and dir  
> being treated separately. So reversing this requirement in HTML5  
> would likely not be compatible with existing content.
>
> Note that dir only affects directionally neutral characters, not  
> characters from scripts with inherent directionality, so there are  
> valid reasons to write text in various languages that uses either  
> dir value.

Directionality also effects tables and block-alignment and related  
display issues.

BTW, can you provide a use-case for setting @dir to the opposite  
value to what a particular script would usually have (i.e., setting  
@dir to 'ltr' for Arabic or Hebrew or 'rtl' for Latin or Cyrillic or  
the like). I cannot think of any use-case myself.

Take care,
Rob
Received on Thursday, 2 August 2007 07:56:56 UTC

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