context: We doubt that John picked up the milk. Chances are about even that Brian is a rhino. It is probably not the case that Greg is a swan.
hypothesis: There is little chance that 'Brian is a rhino and John picked up the milk'.
valid_hypothesis: There is little chance that 'Brian is a rhino and John picked up the milk'.
invalid_hypothesis: It is almost certain that 'Brian is a rhino and John picked up the milk'.
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.
    0.5::factB.
    0.25::factC.
    
  
    %hop2
    conclusion:-and(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is a rhino and John picked up the milk'.