context: Chances are about even that Daniel got the milk. It is likely that Gertrude is a cat. It is probable that Brian is a lion. We doubt that if either 'Brian is a lion' or 'Daniel got the milk' but not both then Julius is white. It is probably the case that if either 'Daniel got the milk' or 'Gertrude is a cat' but not both then Jason is tired. We doubt that if 'Gertrude is a cat and Daniel got the milk' then Fred went to the garden.
hypothesis: There is a better than even chance that either 'Fred went to the garden' or 'Gertrude is a cat' but not both.
valid_hypothesis: There is a better than even chance that either 'Fred went to the garden' or 'Gertrude is a cat' but not both.
invalid_hypothesis: It is improbable that either 'Fred went to the garden' or 'Gertrude is a cat' 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
    0.5::factA.
    0.7::factB.
    0.7::factC.
    %hop1
    0.2::factX:-xor(factC,factA).
    0.7::factY:-xor(factA,factB).
    0.2::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-xor(factZ,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Fred went to the garden' or 'Gertrude is a cat' but not both.