Chances are about even that Lily is green. It is almost certain that John went to the garden. We believe that Julius is white. It is impossible that if 'John went to the garden and Lily is green' then Bill left the milk. Chances are about even that if 'Julius is white and John went to the garden' then Gertrude is a mouse. It is unlikely that if 'John went to the garden' or 'Lily is green' or both then Emily is a wolf.
It is highly unlikely that either 'Emily is a wolf' or 'John went to the garden' but not both.
We believe that either 'Emily is a wolf' or 'John went to the garden' but not both.
It is highly unlikely that either 'Emily is a wolf' or 'John went to the garden' but not both.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.5::factA.
  0.95::factB.
  0.75::factC.
  %hop1
  0.0::factX:-and(factB,factA).
  0.5::factY:-and(factC,factB).
  0.2::factZ:-or(factB,factA).

  %hop2
  conclusion:-xor(factZ,factB).

  query(conclusion).
  
Either 'Emily is a wolf' or 'John went to the garden' but not both.