context: We believe that Greg is a frog. It is highly likely that Brian is a swan. It is likely that Mary got the milk. There is a better than even chance that if either 'Brian is a swan' or 'Mary got the milk' but not both then Winona is a mouse. Chances are slight that if 'Greg is a frog' or 'Brian is a swan' or both then John went to the garden. It is probably not the case that if either 'Mary got the milk' or 'Brian is a swan' but not both then Sumit is tired.
hypothesis: It is unlikely that 'John went to the garden' or 'Mary got the milk' or both.
valid_hypothesis: We believe that 'John went to the garden' or 'Mary got the milk' or both.
invalid_hypothesis: It is unlikely that 'John went to the garden' or 'Mary got 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
    0.75::factA.
    0.9::factB.
    0.7::factC.
    %hop1
    0.6::factX:-xor(factB,factC).
    0.1::factY:-or(factA,factB).
    0.25::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-or(factY,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'John went to the garden' or 'Mary got the milk' or both.