context: Chances are about even that Bernhard is a swan. There is little chance that Lily is white. It is probably not the case that Greg is a lion.
hypothesis: We believe that 'Bernhard is a swan and Lily is white'.
valid_hypothesis: It is highly unlikely that 'Bernhard is a swan and Lily is white'.
invalid_hypothesis: We believe that 'Bernhard is a swan and Lily is white'.
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
    0.5::factA.
    0.1::factB.
    0.25::factC.
    
  
    %hop2
    conclusion:-and(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a swan and Lily is white'.