No no no a thousand times no absolutely not. This is completely out
of the question and conflicts severely with current practice. Making
forms a "separate document type" would grievously wound WWW as it now
exists.
If you don't see this, please look harder.
> The same goes for tables, math, and small inline images. Rather than trying
> to squeeze these into the HTML DTD, we need a way to transmit multiple MIME
> body parts in one transaction.
Likewise for inlined images.
Marc