context: It is probably not the case that Gertrude is a sheep. We doubt that Mary moved to the office. It is improbable that Greg is a swan.
hypothesis: It is probably not the case that either 'Greg is a swan' or 'Gertrude is a sheep' but not both.
valid_hypothesis: It is probably not the case that either 'Greg is a swan' or 'Gertrude is a sheep' but not both.
invalid_hypothesis: It is certain that either 'Greg is a swan' or 'Gertrude is a sheep' 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
    0.25::factA.
    0.2::factB.
    0.1::factC.
    
  
    %hop2
    conclusion:-xor(factC,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is a swan' or 'Gertrude is a sheep' but not both.