context: It is highly likely that Sandra left the milk. There is little chance that Julius is a swan. There is a better than even chance that Brian is a lion. We believe that if 'Julius is a swan' or 'Sandra left the milk' or both then Jessica is a cat. It is likely that if 'Brian is a lion' or 'Julius is a swan' or both then John moved to the office. It is certain that if 'Sandra left the milk' or 'Brian is a lion' or both then Bernhard is a frog.
hypothesis: We believe that either 'Jessica is a cat' or 'Bernhard is a frog' but not both.
valid_hypothesis: It is probably not the case that either 'Jessica is a cat' or 'Bernhard is a frog' but not both.
invalid_hypothesis: We believe that either 'Jessica is a cat' or 'Bernhard is a frog' but not both.
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
    0.9::factA.
    0.1::factB.
    0.6::factC.
    %hop1
    0.75::factX:-or(factB,factA).
    0.7::factY:-or(factC,factB).
    1.0::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-xor(factX,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Jessica is a cat' or 'Bernhard is a frog' but not both.