context: It is improbable that John moved to the office. It is probably not the case that Bernhard is white. It is probably not the case that Lily is a frog. Chances are about even that if either 'John moved to the office' or 'Bernhard is white' but not both then Greg is yellow. There is a better than even chance that if 'John moved to the office and Bernhard is white' then Julius is a swan. It is probably the case that if 'Lily is a frog' or 'Bernhard is white' or both then Mary went to the hallway.
hypothesis: It is probably the case that either 'Julius is a swan' or 'Greg is yellow' but not both.
valid_hypothesis: We doubt that either 'Julius is a swan' or 'Greg is yellow' but not both.
invalid_hypothesis: It is probably the case that either 'Julius is a swan' or 'Greg is yellow' 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
    0.1::factA.
    0.25::factB.
    0.25::factC.
    %hop1
    0.5::factX:-xor(factA,factB).
    0.6::factY:-and(factA,factB).
    0.7::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-xor(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a swan' or 'Greg is yellow' but not both.