context: It is probably the case that Lily is a rhino. There is little chance that Gertrude is a sheep. We believe that Jessica is a cat. It is probably the case that if 'Jessica is a cat and Lily is a rhino' then Bernhard is gray. It is almost certain that if 'Jessica is a cat and Lily is a rhino' then Fred went to the garden. We doubt that if either 'Jessica is a cat' or 'Gertrude is a sheep' but not both then Daniel took the milk.
hypothesis: Chances are about even that either 'Bernhard is gray' or 'Gertrude is a sheep' but not both.
valid_hypothesis: Chances are about even that either 'Bernhard is gray' or 'Gertrude is a sheep' but not both.
invalid_hypothesis: It is certain that either 'Bernhard is gray' or 'Gertrude is a sheep' 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
    0.7::factA.
    0.1::factB.
    0.75::factC.
    %hop1
    0.7::factX:-and(factC,factA).
    0.95::factY:-and(factC,factA).
    0.2::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-xor(factX,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is gray' or 'Gertrude is a sheep' but not both.