context: Chances are slight that John grabbed the apple. It is highly likely that Jeff put down the milk. We believe that Greg is gray.
hypothesis: There is little chance that 'Greg is gray and John grabbed the apple'.
valid_hypothesis: There is little chance that 'Greg is gray and John grabbed the apple'.
invalid_hypothesis: It is certain that 'Greg is gray and John grabbed the apple'.
problog: 
    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.
    0.9::factB.
    0.75::factC.
    
  
    %hop2
    conclusion:-and(factC,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is gray and John grabbed the apple'.