btw (hope this is not off-topic), will there be a 2nd edition
of the XSLT Programmer's Reference? (i could not found an
answer to my question in the 1st edition, but i guess this is
too specific anyway.
but it is still the best book about xslt...)
Actually, the one that is currently on sale is the 2nd edition.
But I am indeed working on a 3rd edition, which will cover XSLT 2.0 and
XPath 2.0. It won't be available for some months though.
I'm sorry you didn't find what you were looking for. The basic
information is all there, but it's always hard to find an answer when
you don't realize what the problem is. Your problem wasn't really about
the union operator, it was the behavior of xsl:value-of.
Michael Kay
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list