context: We doubt that John put down the apple. It is probably the case that Greg is a swan. There is little chance that Brian is white.
hypothesis: It is improbable that 'Greg is a swan and John put down the apple'.
valid_hypothesis: It is improbable that 'Greg is a swan and John put down the apple'.
invalid_hypothesis: There is a better than even chance that 'Greg is a swan 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.
    0.7::factB.
    0.1::factC.
    
  
    %hop2
    conclusion:-and(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and John put down the apple'.