context: It is highly unlikely that John moved to the garden. We believe that Greg is a lion. There is a very good chance that Bernhard is gray. It is probable that if 'Bernhard is gray' or 'Greg is a lion' or both then Sandra left the milk. We doubt that if either 'Greg is a lion' or 'John moved to the garden' but not both then Brian is a frog. There is little chance that if 'John moved to the garden' or 'Greg is a lion' or both then Mary dropped the milk.
hypothesis: We believe that either 'Bernhard is gray' or 'John moved to the garden' but not both.
valid_hypothesis: We believe that either 'Bernhard is gray' or 'John moved to the garden' but not both.
invalid_hypothesis: It is improbable that either 'Bernhard is gray' or 'John moved to the garden' 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
    0.05::factA.
    0.75::factB.
    0.8::factC.
    %hop1
    0.7::factX:-or(factC,factB).
    0.2::factY:-xor(factB,factA).
    0.1::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factC,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is gray' or 'John moved to the garden' but not both.