context: It is unlikely that John went to the hallway. There is almost no chance that Brian is white. It is highly likely that Greg is green. It is improbable that if 'John went to the hallway and Brian is white' then Jessica is a cat. Chances are slight that if either 'Greg is green' or 'John went to the hallway' but not both then Sandra got the football. There is a better than even chance that if either 'Brian is white' or 'John went to the hallway' but not both then Mary left the milk.
hypothesis: It is improbable that either 'Brian is white' or 'Mary left the milk' but not both.
valid_hypothesis: It is improbable that either 'Brian is white' or 'Mary left the milk' but not both.
invalid_hypothesis: It is probable that either 'Brian is white' or 'Mary left 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
    0.2::factA.
    0.02::factB.
    0.9::factC.
    %hop1
    0.1::factX:-and(factA,factB).
    0.1::factY:-xor(factC,factA).
    0.6::factZ:-xor(factB,factA).
  
    %hop2
    conclusion:-xor(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is white' or 'Mary left the milk' but not both.