Robin Fairbains writes:
> let's not lose sight of what we're discussing, though: we need to know
> if the xmlrelated efforts can provide us with models of what we want
> to do within latex, or whether it's too restrictive for the full
> generality of what latex does for people today.
My guess is that most of LaTeX admits rational translations to XML
but not fully regular ones, a metaphorical illusion to some pre20th
century mathematics that is not always well understood.
For example, consider the problem of birationally mapping
P^2 > P^1 X P^1
(where you know what P^N = Ndimensional projective space is, right?)
I claim that we need to follow something like this procedure with
markup. I do not have a proof.
But I think that with successive approximations one will find that the
LaTeX we know and love is a complicated categorical limit of XML's.
 Bill
