context: Chances are slight that John left the milk. We believe that Julius is a lion. It is certain that Mary went to the bedroom. There is a very good chance that if 'Mary went to the bedroom' or 'Julius is a lion' or both then Bernhard is a rhino. It is highly likely that if either 'Mary went to the bedroom' or 'John left the milk' but not both then Greg is yellow. It is highly unlikely that if 'Julius is a lion and John left the milk' then Lily is a swan.
hypothesis: It is probably the case that either 'Julius is a lion' or 'John left the milk' but not both.
valid_hypothesis: It is probably the case that either 'Julius is a lion' or 'John left the milk' but not both.
invalid_hypothesis: It is probably not the case that either 'Julius is a lion' or 'John 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
    0.1::factA.
    0.75::factB.
    1.0::factC.
    %hop1
    0.8::factX:-or(factC,factB).
    0.9::factY:-xor(factC,factA).
    0.05::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-xor(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a lion' or 'John left the milk' but not both.