Chances are about even that Greg is white. It is likely that Bernhard is gray. We believe that Brian is a swan. There is little chance that if 'Brian is a swan' or 'Bernhard is gray' or both then John moved to the garden. It is certain that if either 'Greg is white' or 'Brian is a swan' but not both then Lily is a lion. It is almost certain that if 'Greg is white' or 'Bernhard is gray' or both then Mary went to the bedroom.
There is a very good chance that 'Lily is a lion and Greg is white'.
Chances are slight that 'Lily is a lion and Greg is white'.
There is a very good chance that 'Lily is a lion and Greg is white'.

  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.
  0.7::factB.
  0.75::factC.
  %hop1
  0.1::factX:-or(factC,factB).
  1.0::factY:-xor(factA,factC).
  0.95::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Lily is a lion and Greg is white'.