generate-id() problem

apparantly, as I see it in my code, generate-id is dependent to the
context and the current location in the xml document. that is, when I
use generate-id() twice and in the same context it returns the same
value though I need two different values!

however, when I use generate-id(../..) or generate-id(/) it returns
some other values to me!

is there anything wrong with my settings and assumptions? do I have
any way around it?

thanks,
-Nima