context: There is a very good chance that Julius is a frog. There is a very good chance that Greg is a swan. It is almost certain that Mary put down the apple. It is impossible that if either 'Greg is a swan' or 'Mary put down the apple' but not both then Brian is a lion. It is highly unlikely that if either 'Julius is a frog' or 'Greg is a swan' but not both then Sandra took the milk. It is impossible that if either 'Julius is a frog' or 'Mary put down the apple' but not both then Bernhard is a rhino.
hypothesis: It is unlikely that 'Greg is a swan' or 'Sandra took the milk' or both.
valid_hypothesis: There is a very good chance that 'Greg is a swan' or 'Sandra took the milk' or both.
invalid_hypothesis: It is unlikely that 'Greg is a swan' or 'Sandra took 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
    0.8::factA.
    0.8::factB.
    0.95::factC.
    %hop1
    0.0::factX:-xor(factB,factC).
    0.05::factY:-xor(factA,factB).
    0.0::factZ:-xor(factA,factC).
  
    %hop2
    conclusion:-or(factB,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan' or 'Sandra took the milk' or both.