context: There is almost no chance that Julius is yellow. There is little chance that Lily is a frog. It is probable that John got the apple. It is highly unlikely that if either 'Julius is yellow' or 'Lily is a frog' but not both then Brian is green. Chances are slight that if 'John got the apple and Julius is yellow' then Bernhard is a swan. It is almost certain that if 'Lily is a frog' or 'John got the apple' or both then Sandra left the milk.
hypothesis: It is impossible that 'Bernhard is a swan' or 'Sandra left the milk' or both.
valid_hypothesis: It is probable that 'Bernhard is a swan' or 'Sandra left the milk' or both.
invalid_hypothesis: It is impossible that 'Bernhard is a swan' or 'Sandra left the milk' 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
    0.02::factA.
    0.1::factB.
    0.7::factC.
    %hop1
    0.05::factX:-xor(factA,factB).
    0.1::factY:-and(factC,factA).
    0.95::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-or(factY,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a swan' or 'Sandra left the milk' or both.