context: It is probably not the case that Julius is gray. We believe that Greg is a lion. It is probable that Sandra got the milk. It is highly likely that if either 'Greg is a lion' or 'Julius is gray' but not both then Gertrude is a cat. There is little chance that if 'Greg is a lion' or 'Sandra got the milk' or both then Jeff dropped the apple. It is highly likely that if either 'Julius is gray' or 'Greg is a lion' but not both then Brian is gray.
hypothesis: It is certain that 'Julius is gray' or 'Jeff dropped the apple' or both.
valid_hypothesis: It is probably not the case that 'Julius is gray' or 'Jeff dropped the apple' or both.
invalid_hypothesis: It is certain that 'Julius is gray' or 'Jeff dropped the apple' 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
    0.25::factA.
    0.75::factB.
    0.7::factC.
    %hop1
    0.9::factX:-xor(factB,factA).
    0.1::factY:-or(factB,factC).
    0.9::factZ:-xor(factA,factB).
  
    %hop2
    conclusion:-or(factA,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Julius is gray' or 'Jeff dropped the apple' or both.