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Re: XHTML Basic and XHTML modularization: ACRONYM and BDO

From: Nir Dagan <nir@nirdagan.com>
Date: Tue, 22 Feb 2000 11:33:34 -0500
Message-Id: <200002221630.LAA21071@vega.brown.edu>
To: Jonny Axelsson <jonny@metastasis.net>, www-html@w3.org
At 01:59 PM 2/22/00 +0100, Jonny Axelsson wrote:
>And as for BDO, what is the point with the BDO element, given that every
>applicable element, in particular SPAN, has a DIR attribute? What
>advantages has 
><p><bdo dir="rtl">right to left text direction here.</bdo></p> to 
><p dir="rtl">right to left text direction here.</p>? 
>(substitute any other element for P as needed)

The bdo element and the dir attribute on other elements do completely 
different things.

<bdo> says that characters should be shown in a particular directionality
disregarding the bi-directional algorithm. The dir attribute in other
elements (not in BDO) sets the directionality of neutral characters, 
such as spaces, in order that the browser will apply the bidirectional algorithm 
to the whole thing correctly. Thus, the dir attribute has different semantics 
in BDO and other elements.

That is <span dir="rtl">Nir</span> should be rendered as Nir 
(as there are no neutral characters in the <span> at all; Latin characters 
are all left to right.) 
and <bdo dir="rtl">Nir</bdo> should be rendered as riN. (It doesn't matter that 
these are Latin characters; as the directionality is overridden)

An argument in your favor is that the functionality of BDO is available 
via special bi-di override characters that are a part of HTML's 
character set.

An argument in favor of <bdo> is that if you write "by hand", 
that is in a regular text editor, it is very easy to make mistakes 
of improper nesting. With <bdo> a validator will catch many of 
these errors. With special characters, SGML validators don't 
help for this problem. Special characters are good for 
sophisticated editing Unicode bi-di aware software (which doesn't 
really exists as of now).

Last thing. I actually agree on the ACRONYM ABBR thing. Even if they have 
different semantics, in practice they are used inconsistently by different 
authors, in a way that makes them practically equivalent, say for default 
styling by browsers or for general indexing robots.

Nir Dagan
Assistant Professor of Economics
Brown University 
Providence, RI

Received on Tuesday, 22 February 2000 11:31:00 UTC

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