> However, in my second example,
> 
> ancestor::menu = (//menu)[$pos]
> 
> i can not do
> 
> (count(ancestor::menu|(//menu)[$pos])=1)
> 
> but if my understanding of the union operator is correct, i can make
> 
> (count(ancestor::menu|(//menu)[$pos])=(count(ancestor::menu))
> 
> Right?

Yes. Or you could do

xsl:variable name="P" select="(//menu)[$pos]"
xsl:if test="ancestor::menu[count(.|$P)=1]"

Michael Kay
http://www.saxonica.com/