Re: ... other formats in HTML ...

Anne van Kesteren wrote:
>
> You also mentioned animation. Most animation you see on the Web is of
> presentational nature. 

Not my lot...
Typically I have the problem to provide a text fallback content
for abstract arts (graphical content) or for something like 
concrete poetry (mainly text with specific requirements of
arrangement, timing, etc) or a combination of both. 
This can be done with a combination of external or internal
SVG and a simpler (X)HTML alternative/additional text, somehow 
like concept art.
I discussed this already with an accessibility expert years ago
and this is more or less the conclusion and not really simple
to realise.

> It seems more natural to address that with CSS, 

more with SMIL animation or SMIL animation in SVG

> such as the WebKit animation proposal:
>
>    http://lists.w3.org/Archives/Public/www-style/2007Nov/0090.html
>
> I hope this helps a bit.

There is a ready to implement solution from SMIL, called timesheets:
http://www.w3.org/TR/2007/WD-SMIL3-20070713/smil-timesheets.html

To be used in HTML5 (not XHTML), I think there is unfortunately
a requirement for such an 'alien container' similar as for directly
embedded SVG - the known problem of having XML inside HTML5.
I could not convince the authors/editors to do it completely externally
as possible with CSS.
However, there seems to be no problem for the XHTML variant.
Someone provided already a script solution to show, how it could
work.