It is highly likely that John grabbed the milk. Chances are about even that Bill went to the bedroom. It is impossible that Julius is a frog. It is highly unlikely that if 'Julius is a frog' or 'John grabbed the milk' or both then Greg is white. It is highly unlikely that if either 'John grabbed the milk' or 'Bill went to the bedroom' but not both then Bernhard is a rhino. We believe that if 'Bill went to the bedroom' or 'John grabbed the milk' or both then Mary left the apple.
It is impossible that 'John grabbed the milk and Julius is a frog'.
It is impossible that 'John grabbed the milk and Julius is a frog'.
There is a very good chance that 'John grabbed the milk and Julius is a frog'.

  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
  0.9::factA.
  0.5::factB.
  0.0::factC.
  %hop1
  0.05::factX:-or(factC,factA).
  0.05::factY:-xor(factA,factB).
  0.75::factZ:-or(factB,factA).

  %hop2
  conclusion:-and(factA,factC).

  query(conclusion).
  
'John grabbed the milk and Julius is a frog'.