context: Chances are slight that Mary discarded the apple. It is probably not the case that Lily is a rhino. Chances are about even that Fred is in the school.
hypothesis: There is almost no chance that either 'Fred is in the school' or 'Lily is a rhino' but not both.
valid_hypothesis: Chances are about even that either 'Fred is in the school' or 'Lily is a rhino' but not both.
invalid_hypothesis: There is almost no chance that either 'Fred is in the school' or 'Lily is a rhino' 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
    0.1::factA.
    0.25::factB.
    0.5::factC.
    
  
    %hop2
    conclusion:-xor(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Fred is in the school' or 'Lily is a rhino' but not both.