It is improbable that Mary dropped the apple. We doubt that Julius is white. Chances are slight that Greg is gray. It is unlikely that if 'Julius is white and Greg is gray' then Sandra left the football. We believe that if either 'Mary dropped the apple' or 'Greg is gray' but not both then Brian is a lion. There is little chance that if either 'Julius is white' or 'Greg is gray' but not both then Lily is green.
There is a better than even chance that 'Brian is a lion and Julius is white'.
There is almost no chance that 'Brian is a lion and Julius is white'.
There is a better than even chance that 'Brian is a lion and Julius 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
  0.1::factA.
  0.2::factB.
  0.1::factC.
  %hop1
  0.2::factX:-and(factB,factC).
  0.75::factY:-xor(factA,factC).
  0.1::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Brian is a lion and Julius is white'.