context: It is likely that Greg is a rhino. There is a better than even chance that Sandra left the milk. It is highly likely that Brian is a lion. There is a better than even chance that if either 'Greg is a rhino' or 'Sandra left the milk' but not both then Lily is white. We doubt that if 'Sandra left the milk' or 'Brian is a lion' or both then John went to the office. It is impossible that if either 'Sandra left the milk' or 'Greg is a rhino' but not both then Bernhard is green.
hypothesis: It is certain that 'Brian is a lion and Bernhard is green'.
valid_hypothesis: It is impossible that 'Brian is a lion and Bernhard is green'.
invalid_hypothesis: It is certain that 'Brian is a lion and Bernhard is green'.
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.
    0.6::factB.
    0.9::factC.
    %hop1
    0.6::factX:-xor(factA,factB).
    0.2::factY:-or(factB,factC).
    0.0::factZ:-xor(factB,factA).
  
    %hop2
    conclusion:-and(factC,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is a lion and Bernhard is green'.