context: It is unlikely that Mary dropped the milk. We believe that Jessica is a cat. Chances are about even that John put down the apple.
hypothesis: It is probably the case that 'Mary dropped the milk and John put down the apple'.
valid_hypothesis: There is little chance that 'Mary dropped the milk and John put down the apple'.
invalid_hypothesis: It is probably the case that 'Mary dropped the milk and John put down 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
    0.2::factA.
    0.75::factB.
    0.5::factC.
    
  
    %hop2
    conclusion:-and(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary dropped the milk and John put down the apple'.