context: It is probably the case that Brian is a lion. There is almost no chance that Julius is a swan. We believe that Greg is a frog.
hypothesis: There is almost no chance that 'Julius is a swan and Brian is a lion'.
valid_hypothesis: There is almost no chance that 'Julius is a swan and Brian is a lion'.
invalid_hypothesis: It is certain that 'Julius is a swan and Brian is a lion'.
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
    0.7::factA.
    0.02::factB.
    0.75::factC.
    
  
    %hop2
    conclusion:-and(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Julius is a swan and Brian is a lion'.