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Re: [XHTML2] Specifying alternative resources/content

From: Risto Kankkunen <risto.kankkunen@iki.fi>
Date: Mon, 18 Oct 2004 21:57:12 +0300
Message-ID: <41741208.6070504@iki.fi>
To: www-html@w3.org

> (My example should have been better, e.g. with unique images so that you 
> cannot optimize the common part out of the equation...)

I hope this is a better example of grouped alternative representations:

   <alt>
       <!-- show a graph in vector format -->
       <object src="graph.svg" type="image/svg+xml" />

       <!-- or show it as a bitmap and explanation -->
       <div>
           <p>Could not show a <a href="graph.svg">vector version</a>
               of the graph.
           </p>
           <object src="graph.jpg" type="image/jpeg" />
           <p>This is a low-resoltion bitmap image of the graph that
               unfortunately loses some interesting details. To see a
               close-up of the phenomenon near the upper right corner,
               look at <a href="graph-ur.jpg">this image</a>.
           </p>
       </div>

       <!-- or just as a link -->
       <p>Graph not available at the moment neither in
           <a href="graph.svg">vector</a> or
           <a href="graph.jpg">bitmap</a> format.
       </p>
   </alt>

Here we show either a vector image, a bitmap with an explanation or just 
a text message for the failure. This shows that you can tailor the 
content based on what resources the agent understands and has available, 
which should be important, since the alternative resources are not equal 
and you cannot just replace one with another without possibly losing a 
lot of information. However, that is the model used by the current draft.

Another example showing the possibilities of "<alt>" when used to give 
alternative representation for inline data:

   <alt>
       <math xmlns="http://www.w3.org/1998/Math/MathML">
           <mrow>
               <msup>
                   <mfenced open="[" close="]">
                       <mrow>
                           <mi>a</mi>
                           <mo>+</mo>
                           <mi>b</mi>
                       </mrow>
                   </mfenced>
                   <mn>260</mn>
               </msup>
           </mrow>
       </math>

       <object src="equation.png" type="image/png" />
   </alt>

Here the agent shows an equation using either MathML or, if it doesn't 
support it, as an image. This same situation applies to the multitude of 
ever increasing number of XML sub-languages as well as natural languages 
as I showed in another example.

Regards,
Risto Kankkunen
Received on Monday, 18 October 2004 18:57:08 GMT

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