context: There is little chance that John left the apple. It is improbable that Greg is a frog. Chances are about even that Lily is white. It is almost certain that if 'Greg is a frog and Lily is white' then Brian is gray. It is likely that if 'Greg is a frog and Lily is white' then Bernhard is a lion. It is unlikely that if either 'John left the apple' or 'Greg is a frog' but not both then Julius is a rhino.
hypothesis: Chances are about even that either 'Julius is a rhino' or 'Brian is gray' but not both.
valid_hypothesis: It is highly unlikely that either 'Julius is a rhino' or 'Brian is gray' but not both.
invalid_hypothesis: Chances are about even that either 'Julius is a rhino' or 'Brian is gray' 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.
    0.1::factB.
    0.5::factC.
    %hop1
    0.95::factX:-and(factB,factC).
    0.7::factY:-and(factB,factC).
    0.2::factZ:-xor(factA,factB).
  
    %hop2
    conclusion:-xor(factZ,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a rhino' or 'Brian is gray' but not both.