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BiDi in modularization

From: Nir Dagan <nir@nirdagan.com>
Date: Tue, 01 Feb 2000 18:59:49 -0500
Message-Id: <200002012358.SAA21727@vega.brown.edu>
To: www-html-editor@w3.org
Concerning the handling of BiDi in 


we find:
"4.4.3. BDO Module
The BDO module defines an element that can be used to declare the
bi-directional rules for the element's content."

This is rather inaccurate. In HTML4.0
the bi-directional rules at decided via
* Intristic directionality of characters, and special BiDi control
* HTML markup: the dir attribute (included in i18n attributes) of many
  and the BDO element.
* The above two define the directionality of each character, and rendering
is done based
  on Unicode's bi-directional algorithm.

In other words, having an HTML version without the BDO module 
(e.g. <http://www.w3.org/TR/xhtml-basic/>)
doesn't change much per se the support for bi-dirctionality, as an
identical effect 
of BDO can be achieved by using special control characters, assuming the 
rules of HTML4.0 apply.

In HTML4.0 it is possible to include a Hebrew word in English text in a way
will be rendered correctly by both BiDi and non-BiDi browsers. This can be
by writing the Hebrew word "visually" (backwards) and puting it 
inside a <bdo dir="ltr"></bdo>

Paradoxically, BDO can be used to write documents for browsers that do not 
support BiDi, in a way that would not confuse those who do support it.

So my conclusion is that the BDO module should not exist, and BDO should be
in the basic text module.

Then support for BiDi should be defined in user-agent profiles 
(assuming these can describe things beyond modules).
A non-BiDi browser renders all characters left to right. A BiDi browser
the HTML4.0 BiDi rules. If a document contains little of right to left script
the same BDO'ed variant may be served to both types of client. If it
contains a lot 
probably two different variants are needed.

Nir Dagan
Assistant Professor of Economics
Brown University 
Providence, RI

Received on Tuesday, 1 February 2000 18:58:06 UTC

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