SWF file type for imagedata or videodata - Why not?

I think I have asked something similar before but can't recall getting
reply.  The swf file type does not exist as a valid file type in either
the imagedata or videodata elements.

I want to be able to store data of this file type within these elements.
What is the rationale for this?

What is the work around to this so documents will validate with this
extension? Must be someone else out there wanting to embed Flash movies
as well.

Thanks in advance for any replies.