context: It is certain that Greg is a swan. Chances are slight that Mary took the milk. It is certain that Jason is bored. It is probable that if 'Greg is a swan' or 'Jason is bored' or both then Bernhard is a swan. It is impossible that if either 'Mary took the milk' or 'Greg is a swan' but not both then Sandra dropped the milk. There is little chance that if 'Mary took the milk and Jason is bored' then Julius is a frog.
hypothesis: Chances are slight that 'Julius is a frog' or 'Greg is a swan' or both.
valid_hypothesis: It is certain that 'Julius is a frog' or 'Greg is a swan' or both.
invalid_hypothesis: Chances are slight that 'Julius is a frog' or 'Greg 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
    1.0::factA.
    0.1::factB.
    1.0::factC.
    %hop1
    0.7::factX:-or(factA,factC).
    0.0::factY:-xor(factB,factA).
    0.1::factZ:-and(factB,factC).
  
    %hop2
    conclusion:-or(factZ,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Julius is a frog' or 'Greg is a swan' or both.