context: There is a better than even chance that Mary moved to the office. We doubt that Bernhard is a swan. It is highly likely that Lily is a frog. There is a better than even chance that if either 'Lily is a frog' or 'Bernhard is a swan' but not both then Julius is a swan. Chances are about even that if either 'Mary moved to the office' or 'Bernhard is a swan' but not both then John went to the garden. It is improbable that if 'Mary moved to the office and Bernhard is a swan' then Gertrude is a mouse.
hypothesis: There is a better than even chance that 'Bernhard is a swan' or 'Julius is a swan' or both.
valid_hypothesis: There is a better than even chance that 'Bernhard is a swan' or 'Julius is a swan' or both.
invalid_hypothesis: It is highly unlikely that 'Bernhard is a swan' or 'Julius is a swan' or 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
    0.6::factA.
    0.2::factB.
    0.9::factC.
    %hop1
    0.6::factX:-xor(factC,factB).
    0.5::factY:-xor(factA,factB).
    0.1::factZ:-and(factA,factB).
  
    %hop2
    conclusion:-or(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a swan' or 'Julius is a swan' or both.