context: There is almost no chance that Greg is white. It is improbable that Emily is a wolf. We believe that Lily is a lion. There is a better than even chance that if 'Greg is white and Lily is a lion' then Sandra got the football. It is improbable that if either 'Emily is a wolf' or 'Lily is a lion' but not both then Brian is a swan. Chances are about even that if 'Emily is a wolf' or 'Lily is a lion' or both then Mary went to the office.
hypothesis: Chances are about even that either 'Lily is a lion' or 'Mary went to the office' but not both.
valid_hypothesis: Chances are about even that either 'Lily is a lion' or 'Mary went to the office' but not both.
invalid_hypothesis: It is impossible that either 'Lily is a lion' or 'Mary 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
    0.02::factA.
    0.1::factB.
    0.75::factC.
    %hop1
    0.6::factX:-and(factA,factC).
    0.1::factY:-xor(factB,factC).
    0.5::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-xor(factC,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Lily is a lion' or 'Mary went to the office' but not both.