context: It is highly unlikely that Brian is a swan. It is highly likely that Mary got the football. Chances are slight that Bernhard is white. Chances are slight that if 'Brian is a swan' or 'Bernhard is white' or both then Jessica is a mouse. It is highly likely that if 'Mary got the football' or 'Brian is a swan' or both then Greg is white. It is impossible that if 'Brian is a swan' or 'Mary got the football' or both then John went to the garden.
hypothesis: There is little chance that either 'Mary got the football' or 'Bernhard is white' but not both.
valid_hypothesis: There is a very good chance that either 'Mary got the football' or 'Bernhard is white' but not both.
invalid_hypothesis: There is little chance that either 'Mary got the football' or 'Bernhard is white' 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
    0.05::factA.
    0.9::factB.
    0.1::factC.
    %hop1
    0.1::factX:-or(factA,factC).
    0.9::factY:-or(factB,factA).
    0.0::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary got the football' or 'Bernhard is white' but not both.