context: There is a very good chance that Brian is white. There is little chance that Gertrude is a mouse. It is probable that John went to the office. We doubt that if 'Gertrude is a mouse and Brian is white' then Lily is a rhino. Chances are slight that if 'Gertrude is a mouse' or 'John went to the office' or both then Mary left the football. It is certain that if 'John went to the office and Gertrude is a mouse' then Bernhard is a lion.
hypothesis: There is a better than even chance that either 'Mary left the football' or 'John went to the office' but not both.
valid_hypothesis: There is a better than even chance that either 'Mary left the football' or 'John went to the office' but not both.
invalid_hypothesis: It is improbable that either 'Mary left the football' or 'John went to the office' 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
    0.8::factA.
    0.1::factB.
    0.7::factC.
    %hop1
    0.2::factX:-and(factB,factA).
    0.1::factY:-or(factB,factC).
    1.0::factZ:-and(factC,factB).
  
    %hop2
    conclusion:-xor(factY,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary left the football' or 'John went to the office' but not both.