It is unlikely that Lily is green. It is highly likely that Greg is a lion. Chances are slight that Julius is a rhino. It is probably the case that if either 'Lily is green' or 'Greg is a lion' but not both then Mary left the football. It is highly unlikely that if 'Greg is a lion' or 'Julius is a rhino' or both then John picked up the milk. There is little chance that if either 'Lily is green' or 'Greg is a lion' but not both then Bernhard is a swan.
It is probably not the case that 'Lily is green' or 'Bernhard is a swan' or both.
It is probably not the case that 'Lily is green' or 'Bernhard is a swan' or both.
It is certain that 'Lily is green' or 'Bernhard is a swan' or 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
  0.2::factA.
  0.9::factB.
  0.1::factC.
  %hop1
  0.7::factX:-xor(factA,factB).
  0.05::factY:-or(factB,factC).
  0.1::factZ:-xor(factA,factB).

  %hop2
  conclusion:-or(factA,factZ).

  query(conclusion).
  
'Lily is green' or 'Bernhard is a swan' or both.