Where can I find it?
on my machine:-)
It's an update of unicode.xml as found, for example, here
http://www.w3.org/2003/entities/xml/
but it's quite a bit bigger (as I added all the information from the
Unicode 5 version of the Unicode Character data file, and I added the
client side XSLT transform to HTML, because someone asked for it.
I'll make it public once I've had chance to check the right numbers are
in the right places, but probably not for a week or so. Depends on when
we can get the next draft of MathML3 out.

I would like to make some tests with that file, to get a feeling for
the time the XSLT processing needs. It sounds ideal for that purpose
and to get it online in a few weeks would be fine with me.