context: Chances are about even that Julius is gray. There is little chance that Sandra dropped the milk. It is impossible that Greg is yellow.
hypothesis: It is impossible that 'Sandra dropped the milk and Greg is yellow'.
valid_hypothesis: It is impossible that 'Sandra dropped the milk and Greg is yellow'.
invalid_hypothesis: It is probable that 'Sandra dropped the milk and Greg is yellow'.
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
    0.5::factA.
    0.1::factB.
    0.0::factC.
    
  
    %hop2
    conclusion:-and(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Sandra dropped the milk and Greg is yellow'.