context: There is little chance that Greg is a swan. It is highly unlikely that Brian is a frog. It is probably not the case that Jeff left the apple.
hypothesis: There is a very good chance that 'Brian is a frog and Greg is a swan'.
valid_hypothesis: It is impossible that 'Brian is a frog and Greg is a swan'.
invalid_hypothesis: There is a very good chance that 'Brian is a frog and Greg is a swan'.
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.
    0.05::factB.
    0.25::factC.
    
  
    %hop2
    conclusion:-and(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is a frog and Greg is a swan'.