XOR conditionals

G'day,

Is it possible to do XOR conditionals in docbook (xsltproc)?

I have a subsection of a document that I want to do this:

	if condition=html 
		publish it

	if conditional=pdf
		DONT publish it

	if condition=FOO
		ONLY publish the subsection, and not the rest of the document

I have the first two working fine, and I could just spin off the
subsection into a redundant, separate document, but I'd rather not have
to maintain two docs that way.

Any thoughts?

Thanks,

Jens