context: It is probable that Bernhard is a swan. It is improbable that Brian is a rhino. There is a better than even chance that Julius is a swan. It is certain that if 'Brian is a rhino and Bernhard is a swan' then John moved to the garden. It is probably the case that if either 'Brian is a rhino' or 'Julius is a swan' but not both then Emily is a sheep. Chances are about even that if either 'Brian is a rhino' or 'Bernhard is a swan' but not both then Gertrude is a cat.
hypothesis: There is little chance that either 'Julius is a swan' or 'Brian is a rhino' but not both.
valid_hypothesis: There is a better than even chance that either 'Julius is a swan' or 'Brian is a rhino' but not both.
invalid_hypothesis: There is little chance that either 'Julius is a swan' or 'Brian is a rhino' 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.
    0.6::factC.
    %hop1
    1.0::factX:-and(factB,factA).
    0.7::factY:-xor(factB,factC).
    0.5::factZ:-xor(factB,factA).
  
    %hop2
    conclusion:-xor(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a swan' or 'Brian is a rhino' but not both.