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Re: [XHTML2] Specifying alternative resources/content

From: Risto Kankkunen <risto.kankkunen@iki.fi>
Date: Tue, 19 Oct 2004 18:49:35 +0300
To: www-html@w3.org
Message-ID: <4175378F.1020005@iki.fi>

>>>In the proposal above, the user agent has to look inside the <div/>
>>
>> > element, and if it reports that it can accept JPEG but not MP3, it
>> > has to reject that block altogether and go to the next one?
>>
>>Right.
> 
> That requires look-ahead, which is not something to be encouraged, as
> it frustrates incremental rendering.

Look-ahead is not nice, IF it can be avoided. But the agent has to parse 
the <div> anyway first, because it doesn't know whether it's gonna fail. 
If it's going to find that it cannot render the page, would you really 
want it to keep all the partial stuff rather than scrap the junk to 
avoid confusion, just to save a few seconds?

I think the user agent is much faster trying out what combination 
satisfies the document author's intent than the user. If it takes a 
couple more seconds to render the page, but I get a complete page in the 
end automatically, I'm willing to wait.

Here is an example of picking an image from a number of mirror servers. 
I'd rather let my browser do the picking according to the instructions 
of the document author rather than try out each mirror by hand. If you 
can come up with an algorithm that does this without look-ahead, please 
tell me.

Again, "<alt>" doesn't require look-ahead any more than the current 
draft proposal, but it makes possible to use look-ahead in scenarios 
that the proposal doesn't handle at all.

   <section>
   <h>Screenshots</h>
   <alt>
       <div xml:base="http://mirror1.example.net/">
           <a href="pic001.jpeg">
               <object src="pic001-thumb.jpg type="image/jpeg" />
           </a>
           <a href="pic002.html">Next</a>
       </div>

       <div xml:base="http://mirror2.example.net/">
           <a href="pic001.jpeg">
               <object src="pic001-thumb.jpg type="image/jpeg" />
           </a>
           <a href="pic002.html">Next</a>
       </div>

       <div xml:base="http://mirror3.example.net/">
           <a href="pic001.jpeg">
               <object src="pic001-thumb.jpg type="image/jpeg" />
           </a>
           <a href="pic002.html">Next</a>
       </div>

       <div xml:base="http://mirror4.example.net/">
           <a href="pic001.jpeg">
               <object src="pic001-thumb.jpg type="image/jpeg" />
           </a>
           <a href="pic002.html">Next</a>
       </div>
   </alt>
   </section>
Received on Tuesday, 19 October 2004 15:49:38 GMT

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