context: There is almost no chance that Daniel put down the milk. It is improbable that Sandra dropped the milk. Chances are about even that Lily is a lion. It is highly likely that if 'Sandra dropped the milk and Lily is a lion' then Bernhard is gray. We believe that if 'Sandra dropped the milk' or 'Lily is a lion' or both then Mary moved to the garden. There is a better than even chance that if 'Daniel put down the milk' or 'Lily is a lion' or both then Greg is yellow.
hypothesis: It is highly unlikely that 'Greg is yellow' or 'Sandra dropped the milk' or both.
valid_hypothesis: Chances are about even that 'Greg is yellow' or 'Sandra dropped the milk' or both.
invalid_hypothesis: It is highly unlikely that 'Greg is yellow' or 'Sandra dropped 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.
    0.5::factC.
    %hop1
    0.9::factX:-and(factB,factC).
    0.75::factY:-or(factB,factC).
    0.6::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-or(factZ,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is yellow' or 'Sandra dropped the milk' or both.