context: There is a very good chance that Brian is white. It is highly likely that Fred dropped the milk. There is a better than even chance that Lily is a frog. It is highly unlikely that if 'Lily is a frog and Fred dropped the milk' then Julius is a rhino. There is almost no chance that if either 'Fred dropped the milk' or 'Lily is a frog' but not both then Mary went to the office. It is probably not the case that if 'Fred dropped the milk' or 'Lily is a frog' or both then Greg is a swan.
hypothesis: There is little chance that 'Fred dropped the milk' or 'Greg is a swan' or both.
valid_hypothesis: It is highly likely that 'Fred dropped the milk' or 'Greg is a swan' or both.
invalid_hypothesis: There is little chance that 'Fred dropped the milk' 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
    0.8::factA.
    0.9::factB.
    0.6::factC.
    %hop1
    0.05::factX:-and(factC,factB).
    0.02::factY:-xor(factB,factC).
    0.25::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-or(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Fred dropped the milk' or 'Greg is a swan' or both.