Sorry to be dense, but ...
SMIL is multimedia - any kind of multimedia, including still images, sound, and animation, and transitions between any of these.
Inkscape is a 2D drawing program that among other things renders SVG.
What are you all trying to accomplish here? Is the goal to get Inkscape to render SMIL, complete with fades, sounds, and embedded movies, or is it to make Inkscape more SMIL friendly, so that it can be used from within SMIL to render those sorts of objects it already supports? Or something else entirely?
For instance, and this really doesn't have to apply to just SMIL, I can imagine extensions for inkscape that would aid in creating animations: given drawing A and drawing F, interpolate in steps the sizes, positions, and orientations of all objects to fill in intervening drawings B,C,D,E. Most likely that wouldn't be adequate, and some sort of trajectories would have to be used, and different trajectories would be applied to groups of objects. But that isn't very complicated, it is just the automated stepwise application of a transform to existing elements, and it does not require adding an explicit time value to objects. However, for Inkscape to do anything much with SMIL it would seem like it would have to go from (x,y) to (x,y,t) for pretty much every visible object, and that seems like a pretty major change to make for what may be a niche application.
Regards,
David Mathog mathog@...1176... Manager, Sequence Analysis Facility, Biology Division, Caltech