It is probable that Mary went to the bedroom. It is probably the case that Julius is gray. It is impossible that John left the milk. It is highly unlikely that if 'Julius is gray' or 'Mary went to the bedroom' or both then Brian is a rhino. It is almost certain that if 'John left the milk' or 'Mary went to the bedroom' or both then Lily is a lion. There is a better than even chance that if 'John left the milk and Julius is gray' then Bernhard is a frog.
It is highly unlikely that 'John left the milk' or 'Brian is a rhino' or both.
It is highly unlikely that 'John left the milk' or 'Brian is a rhino' or both.
It is probably the case that 'John left the milk' or 'Brian is a rhino' 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
  0.7::factA.
  0.7::factB.
  0.0::factC.
  %hop1
  0.05::factX:-or(factB,factA).
  0.95::factY:-or(factC,factA).
  0.6::factZ:-and(factC,factB).

  %hop2
  conclusion:-or(factC,factX).

  query(conclusion).
  
'John left the milk' or 'Brian is a rhino' or both.