There is little chance that Greg is white. It is certain that John dropped the apple. There is little chance that Lily is yellow. It is probable that if 'Greg is white' or 'John dropped the apple' or both then Mary went to the bedroom. We believe that if 'Lily is yellow and John dropped the apple' then Brian is green. It is likely that if 'John dropped the apple and Lily is yellow' then Bernhard is a frog.
Chances are slight that 'John dropped the apple and Lily is yellow'.
Chances are slight that 'John dropped the apple and Lily is yellow'.
It is highly likely that 'John dropped the apple and Lily is yellow'.

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

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

  query(conclusion).
  
'John dropped the apple and Lily is yellow'.