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Re: Content negotiation example needed.

From: Nir Dagan <nir@nirdagan.com>
Date: Sat, 11 Sep 1999 09:39:15 -0400
Message-Id: <199909111338.JAA16005@dark.brown.edu>
To: Chuck Letourneau <cpl@starlingweb.com>, w3c-wai-gl@w3.org
I think that the intention of the example in the techniques document 
referred to HTTP content negotiation based on the accept-language header 
sent by the client.

The client requested:

host: www.w3.org
user-agent: Moozillah/6.3
accept-language: fr,it

The server then based on the accept-language header should return 
a French document if it has one, an Italian one if French is not available 
but Italian is. In case it doesn't have any, the server may either return
a document in a third language, with a 200 OK status, this makes sense if
the document
is available in only one language anyway.

The server may instead return a 406 error code and a document listing the 
available alternatives:

HTTP/1.1 406 Not acceptable
content-type: text/html;charset=iso-8859-1
server: ServerDuJour/4.8
content-language: en

<title>We have only other languages!</title>
<p>We have only an <a href="english.html">English version</a>
and a <a href="spanish.html">Spanish version.</a>

The WAI may like to take a position on related issues:
The latest version of HTTP/1.1, RFC2616 http://www.ietf.org/rfc/rfc2616.txt 
actually considers the user-agent request header as well as legitimate for 
conducting content negotiation.

Also it is possible to learn about the clients capabilities with
client-side scripts 
(often more than with HTTP) so there may be room for some guidelines on
this too.

One problem with HTTP examples is that they leave the reader clueless in
to how to practically implement them with the server that he/she is using. 
So it would be desirable to give reference to various servers' documantation 
on the matter.


At 10:04 PM 9/10/99 -0400, Chuck Letourneau wrote:
>For Checkpoint 11.3, "Provide information so that users may receive documents
>according to their preferences"
>The Techniques Document has the following example:
>"1) Instead of including links such as "Here is the French version of this
>document", use content negotiation so that the French version is served to
>clients requesting French versions of documents."
>I have never seen markup (or scripting) that actually shows how to do content
>negotiation.  I honestly don't even know if it is only something that can be
>done server-side or if it can be done client-side. 
>I need to include a meaningful example in the EO WCAG Curriculum that will
>students how to actually do it (or what it means to be able to do it), and
>able to explain the concept in a few words.  
>I also can't think of any reason that the same example couldn't be
included in
>the WCAG Techniques document, since the current example isn't really an
>at all.
>Thanks in advance,
>Chuck Letourneau
>Starling Access Services
> "Access A World Of Possibility"
>  e-mail: info@starlingweb.com
>   URL: http://www.starlingweb.com
>    Phone: 613-820-2272  FAX: 613-820-6983
Nir Dagan
Assistant Professor of Economics
Brown University 
Providence, RI

Received on Saturday, 11 September 1999 09:38:19 UTC

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