context: Chances are about even that Bernhard is a swan. It is unlikely that Daniel got the football. It is certain that Jessica is a sheep.
hypothesis: We believe that 'Daniel got the football and Jessica is a sheep'.
valid_hypothesis: We doubt that 'Daniel got the football and Jessica is a sheep'.
invalid_hypothesis: We believe that 'Daniel got the football and Jessica is a sheep'.
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.
    0.2::factB.
    1.0::factC.
    
  
    %hop2
    conclusion:-and(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Daniel got the football and Jessica is a sheep'.