context: It is probable that Julius is a lion. It is highly likely that John discarded the apple. We believe that Mary took the football.
hypothesis: Chances are about even that either 'Julius is a lion' or 'Mary took the football' but not both.
valid_hypothesis: Chances are about even that either 'Julius is a lion' or 'Mary took the football' but not both.
invalid_hypothesis: It is almost certain that either 'Julius is a lion' or 'Mary took the football' 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.
    0.9::factB.
    0.75::factC.
    
  
    %hop2
    conclusion:-xor(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a lion' or 'Mary took the football' but not both.