context: It is probably not the case that Lily is a frog. It is probably not the case that Brian is a swan. It is likely that Julius is a lion. There is almost no chance that if 'Lily is a frog' or 'Brian is a swan' or both then John took the football. It is likely that if 'Brian is a swan and Lily is a frog' then Greg is a rhino. It is almost certain that if 'Brian is a swan' or 'Julius is a lion' or both then Mary left the milk.
hypothesis: It is highly likely that either 'Brian is a swan' or 'Lily is a frog' but not both.
valid_hypothesis: It is probably not the case that either 'Brian is a swan' or 'Lily is a frog' but not both.
invalid_hypothesis: It is highly likely that either 'Brian is a swan' or 'Lily is a frog' 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
    0.25::factA.
    0.25::factB.
    0.7::factC.
    %hop1
    0.02::factX:-or(factA,factB).
    0.7::factY:-and(factB,factA).
    0.95::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-xor(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is a swan' or 'Lily is a frog' but not both.