There is little chance that Fred is in the cinema. There is little chance that John went to the bedroom. It is likely that Brian is a lion. It is highly unlikely that if 'Fred is in the cinema' or 'Brian is a lion' or both then Julius is green. It is impossible that if either 'Fred is in the cinema' or 'John went to the bedroom' but not both then Mary dropped the milk. We believe that if 'Brian is a lion and John went to the bedroom' then Lily is a frog.
It is highly unlikely that 'Brian is a lion and Lily is a frog'.
It is highly unlikely that 'Brian is a lion and Lily is a frog'.
There is a very good chance that 'Brian is a lion and Lily 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
  0.1::factA.
  0.1::factB.
  0.7::factC.
  %hop1
  0.05::factX:-or(factA,factC).
  0.0::factY:-xor(factA,factB).
  0.75::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Brian is a lion and Lily is a frog'.