context: It is almost certain that Lily is a swan. Chances are slight that Mary went to the office. It is probably not the case that Greg is green. It is improbable that if 'Lily is a swan' or 'Mary went to the office' or both then Emily is a sheep. We doubt that if 'Greg is green' or 'Lily is a swan' or both then Sandra got the football. Chances are slight that if either 'Lily is a swan' or 'Mary went to the office' but not both then John dropped the milk.
hypothesis: We doubt that either 'Mary went to the office' or 'John dropped the milk' but not both.
valid_hypothesis: We doubt that either 'Mary went to the office' or 'John dropped the milk' but not both.
invalid_hypothesis: It is probably the case that either 'Mary went to the office' or 'John dropped 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
    0.95::factA.
    0.1::factB.
    0.25::factC.
    %hop1
    0.1::factX:-or(factA,factB).
    0.2::factY:-or(factC,factA).
    0.1::factZ:-xor(factA,factB).
  
    %hop2
    conclusion:-xor(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary went to the office' or 'John dropped the milk' but not both.