context: It is probably the case that Bernhard is a frog. There is little chance that Lily is a swan. There is a better than even chance that Brian is a rhino. There is a better than even chance that if 'Bernhard is a frog and Brian is a rhino' then Daniel took the football. It is impossible that if 'Brian is a rhino and Bernhard is a frog' then Mary moved to the garden. It is certain that if either 'Bernhard is a frog' or 'Brian is a rhino' but not both then Julius is gray.
hypothesis: It is improbable that either 'Brian is a rhino' or 'Julius is gray' but not both.
valid_hypothesis: It is probably the case that either 'Brian is a rhino' or 'Julius is gray' but not both.
invalid_hypothesis: It is improbable that either 'Brian is a rhino' or 'Julius 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
    0.7::factA.
    0.1::factB.
    0.6::factC.
    %hop1
    0.6::factX:-and(factA,factC).
    0.0::factY:-and(factC,factA).
    1.0::factZ:-xor(factA,factC).
  
    %hop2
    conclusion:-xor(factC,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is a rhino' or 'Julius is gray' but not both.