> >how do you do without markup in this case:
> >
> >  The $a$ in the formula is a variable
>
> The usual remark on this: Can you parse it? :-) -- If you can parse it, it
> must be possible. Right?

quite.

when i was first thinking of switching to computer science (from
mathematics) i went to the central library of the large city where my
parents lived, and read all the books they had on computing.  one
(written ca. 1952, iirc) included a detailed description of the
authors' algorithms for understanding and then translating natural
languages.

my first job, in 1968, was in an institute whose primary research
"product" was a natural language parser.

for two or more decades, this department has run a large (and pretty
successful, by its own lights) group of researchers who study the same
problems.

none of these groups has yet "finished the job".  they have some
interesting results, but probably could not parse the awful english
that i write.

can we practically hypothecate a markup language that depends on
comprehending natural language?

surely not, even in the hans aberg universe?

robin