context: It is highly likely that Greg is gray. There is a better than even chance that Brian is a rhino. We believe that Lily is green. It is highly unlikely that if 'Brian is a rhino and Lily is green' then John moved to the garden. We believe that if 'Greg is gray' or 'Brian is a rhino' or both then Mary dropped the milk. It is highly unlikely that if 'Brian is a rhino' or 'Lily is green' or both then Julius is a lion.
hypothesis: It is almost certain that 'Greg is gray' or 'Mary dropped the milk' or both.
valid_hypothesis: It is almost certain that 'Greg is gray' or 'Mary dropped the milk' or both.
invalid_hypothesis: It is improbable that 'Greg is gray' or 'Mary 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
    0.9::factA.
    0.6::factB.
    0.75::factC.
    %hop1
    0.05::factX:-and(factB,factC).
    0.75::factY:-or(factA,factB).
    0.05::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-or(factA,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is gray' or 'Mary dropped the milk' or both.