Hi,
 I have my own tool 

 That's what I need to dig in my previous projects 

_0_ is your identifier to inject a value in the xpath.
so 'books[@category="_0_"]' is really something you want to be 
books[@category="My own category"]
and so _0_ means that I will look at the first variable defined and replace _0_ with its value.
 does that make sense?
xml proxy doesn't beed to be blank and can be anywhere, but a top level gameobject is a good start, then you can complexify this aspect, right now only try to go straight to a result.
bye,
 Jean
bye,
Jean