context: It is highly unlikely that Julius is a swan. There is little chance that Jessica is a sheep. We believe that Bernhard is green. It is improbable that if either 'Jessica is a sheep' or 'Bernhard is green' but not both then Mary put down the apple. It is likely that if either 'Jessica is a sheep' or 'Julius is a swan' but not both then Brian is white. There is almost no chance that if 'Bernhard is green' or 'Jessica is a sheep' or both then John grabbed the milk.
hypothesis: Chances are slight that 'Brian is white' or 'Julius is a swan' or both.
valid_hypothesis: Chances are slight that 'Brian is white' or 'Julius is a swan' or both.
invalid_hypothesis: It is certain that 'Brian is white' or 'Julius is a swan' or 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
    0.05::factA.
    0.1::factB.
    0.75::factC.
    %hop1
    0.1::factX:-xor(factB,factC).
    0.7::factY:-xor(factB,factA).
    0.02::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-or(factY,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is white' or 'Julius is a swan' or both.