data source as parameter?

I've been toying around with some stuff lately, and I must say, I
really like XSL :)

One thing I tried, is loading up a couple of data sources and
transforming them into the same stylesheet.  Basically, what I did,
which feels very hack-ish, but firefox let me do it... is I set one of
the data sources as a parameter to the stylesheet, then transformed the
other data source with the document.

Here's the 'proof of concept' code I wrote to see if it was even
possible:
http://edge.scriptkitchen.com:81/~kitchen/xsl/cute3/cutetest.html (I
was feeling 'cute' for some reason...)

Now, my question is:  Is this legit?  Am I supposed to be able to do
this?  I tried it in Opera (9.02) and saw that it worked there as well,
so I can only assume so.. but I wanted to get an answer straight from
the horse's mouth, so to speak.

If it is legit.. this is EXTREMELY handy :)  I was able to do what I
wanted another way, but it was even more hack-ish, and destroyed the
two source documents...

Thanks!

-Jeremy