context: There is a better than even chance that Greg is yellow. It is highly likely that Sandra left the milk. We believe that Brian is a swan. It is probable that if 'Greg is yellow' or 'Sandra left the milk' or both then Julius is a lion. There is a better than even chance that if 'Greg is yellow' or 'Brian is a swan' or both then John dropped the apple. Chances are about even that if 'Brian is a swan' or 'Sandra left the milk' or both then Lily is a rhino.
hypothesis: Chances are slight that 'Julius is a lion' or 'Lily is a rhino' or both.
valid_hypothesis: There is a very good chance that 'Julius is a lion' or 'Lily is a rhino' or both.
invalid_hypothesis: Chances are slight that 'Julius is a lion' or 'Lily is a rhino' 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
    0.6::factA.
    0.9::factB.
    0.75::factC.
    %hop1
    0.7::factX:-or(factA,factB).
    0.6::factY:-or(factA,factC).
    0.5::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-or(factX,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Julius is a lion' or 'Lily is a rhino' or both.