context: It is impossible that John moved to the office. We doubt that Brian is gray. There is a better than even chance that Jessica is a cat. It is improbable that if 'Jessica is a cat' or 'Brian is gray' or both then Bernhard is a frog. We believe that if 'Brian is gray and Jessica is a cat' then Greg is white. It is certain that if 'John moved to the office and Jessica is a cat' then Daniel left the milk.
hypothesis: It is impossible that either 'John moved to the office' or 'Daniel left the milk' but not both.
valid_hypothesis: It is impossible that either 'John moved to the office' or 'Daniel left the milk' but not both.
invalid_hypothesis: Chances are about even that either 'John moved to the office' or 'Daniel 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
    0.0::factA.
    0.2::factB.
    0.6::factC.
    %hop1
    0.1::factX:-or(factC,factB).
    0.75::factY:-and(factB,factC).
    1.0::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-xor(factA,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'John moved to the office' or 'Daniel left the milk' but not both.