Dear Jin Xu,
you could try two things, the first is add a filesharing application
to the xml-file, this should generate some lookups.
The second thing is that you initiate some lookups randomly. The
easiest way to do this is by taking a look at some other action diles
than pastry (I think napster does this).
(A third way would be a randomLookupGenerator, but sadly only Chord
has one at the moment)