context: There is little chance that Winona is a sheep. It is probably not the case that Bernhard is green. It is impossible that Mary left the football. We doubt that if 'Bernhard is green and Mary left the football' then Fred is in the school. It is impossible that if 'Bernhard is green' or 'Winona is a sheep' or both then Bill went to the garden. It is likely that if 'Winona is a sheep' or 'Mary left the football' or both then John put down the milk.
hypothesis: It is highly unlikely that either 'Mary left the football' or 'John put down the milk' but not both.
valid_hypothesis: It is highly unlikely that either 'Mary left the football' or 'John put down the milk' but not both.
invalid_hypothesis: We believe that either 'Mary left the football' or 'John put down the milk' 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.
    0.0::factC.
    %hop1
    0.2::factX:-and(factB,factC).
    0.0::factY:-or(factB,factA).
    0.7::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-xor(factC,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary left the football' or 'John put down the milk' but not both.