context: It is highly unlikely that Greg is white. There is almost no chance that John went to the hallway. There is almost no chance that Brian is a rhino. It is almost certain that if 'John went to the hallway and Brian is a rhino' then Gertrude is a mouse. It is highly unlikely that if either 'John went to the hallway' or 'Greg is white' but not both then Julius is a frog. There is a very good chance that if either 'Brian is a rhino' or 'Greg is white' but not both then Bernhard is a swan.
hypothesis: It is probable that either 'Bernhard is a swan' or 'Brian is a rhino' but not both.
valid_hypothesis: It is highly unlikely that either 'Bernhard is a swan' or 'Brian is a rhino' but not both.
invalid_hypothesis: It is probable that either 'Bernhard 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
    0.05::factA.
    0.02::factB.
    0.02::factC.
    %hop1
    0.95::factX:-and(factB,factC).
    0.05::factY:-xor(factB,factA).
    0.8::factZ:-xor(factC,factA).
  
    %hop2
    conclusion:-xor(factZ,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is a swan' or 'Brian is a rhino' but not both.