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Re: FAQ: CSS vs. markup for bidi support

From: Bert Bos <bert@w3.org>
Date: Tue, 28 Aug 2007 17:58:46 +0200
To: 'WWW International' <www-international@w3.org>
Cc: fantasai <fantasai.lists@inkedblade.net>, 'Richard Ishida' <ishida@w3.org>
Message-Id: <200708281758.46680.bert@w3.org>

On Tuesday 28 August 2007 16:22, fantasai wrote:
> I was looking at
>    http://www.w3.org/International/questions/qa-bidi-css-markup
> yesterday and noticed that there's still a major error in this
> section:
> http://www.w3.org/International/questions/qa-bidi-css-markup#xhtml
> Specifically, because namespacing allows XHTML to be recognized as
> XHTML even in compound documents, XHTML 'dir' attributes should work
> in browsers even when the document is served as XML.

That's not so clear. I think you should distinguish known document types 
from generic XML.

The meaning of every bit of mark-up depends on the context in which it 
is used, starting from the MIME type of the document as a whole. E.g., 
the fact that

    <h:li>The second item.</h:li>

is displayed as

    2. The second item.

is not because the meaning of h:li elements is to display "2.", but 
because it happens to be the second element in another element that 
happens to be a list in the context of this document.

Namespaces are no different from attributes in that respect. They are 
more difficult to understand and handle because they are inherited and 
abbreviated, but otherwise they are just mark-up, i.e., syntax, without 
any inherent, context-independent meaning. E.g., a namespace in an XSLT 
document has a very different function from one in an RDF document, 
which is again different from a WICD.

It is, of course, bad practice to use namespaces in unexpected ways in 
different documents, just as it is bad practice to use the "wrong" 
names for elements (you don't call a list item <red-cow>, even though 
the computer doesn't care), but sometimes it's unavoidable.

Which means, in brief, that seeing an h:dir attribute outside of XHTML 
(where h is the namespace of XHTML, which I don't know by heart), 
*suggests* that the enclosing element is to be rendered with a certain 
writing direction, but you can't be sure, unless you start with the 
MIME type and that MIME type's RFC and work your way through the 
document with the specification in hand.

A text/xml or application/xml document has, by definition, no meaning 
other than what the style sheet PI (if any) provides. XHTML 
(application/xhtml+xml), however, *does* have meaning. The XHTML 
specification says pretty much that the meaning of the mark-up is the 
same as that of similar HTML mark-up.

So I agree that the quoted FAQ is incorrect for XHTML ("dir" works 
without any style rules), but I believe it is correct for generic XML 
("dir" needs style rules to work).

  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Tuesday, 28 August 2007 15:58:57 UTC

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