context: It is likely that Mary left the football. It is probably not the case that John got the apple. It is probable that Greg is a rhino.
hypothesis: It is improbable that either 'Greg is a rhino' or 'John got the apple' but not both.
valid_hypothesis: There is a better than even chance that either 'Greg is a rhino' or 'John got the apple' but not both.
invalid_hypothesis: It is improbable that either 'Greg is a rhino' or 'John got 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
    0.7::factA.
    0.25::factB.
    0.7::factC.
    
  
    %hop2
    conclusion:-xor(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is a rhino' or 'John got the apple' but not both.