context: There is a better than even chance that Greg is a lion. Chances are slight that Fred went to the garden. Chances are slight that Sandra dropped the apple.
hypothesis: It is unlikely that either 'Fred went to the garden' or 'Sandra dropped the apple' but not both.
valid_hypothesis: It is unlikely that either 'Fred went to the garden' or 'Sandra dropped the apple' but not both.
invalid_hypothesis: It is probable that either 'Fred went to the garden' or 'Sandra dropped the apple' but not 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.
    0.1::factB.
    0.1::factC.
    
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Fred went to the garden' or 'Sandra dropped the apple' but not both.