context: It is almost certain that Mary dropped the milk. It is improbable that Fred left the football. Chances are slight that Julius is a frog.
hypothesis: It is highly likely that either 'Fred left the football' or 'Mary dropped the milk' but not both.
valid_hypothesis: It is highly likely that either 'Fred left the football' or 'Mary dropped the milk' but not both.
invalid_hypothesis: There is little chance that either 'Fred left the football' or 'Mary dropped the milk' 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
    0.95::factA.
    0.1::factB.
    0.1::factC.
    
  
    %hop2
    conclusion:-xor(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Fred left the football' or 'Mary dropped the milk' but not both.