context: It is likely that Greg is a swan. We doubt that Jeff dropped the apple. It is unlikely that John took the football. There is a better than even chance that if 'Greg is a swan and Jeff dropped the apple' then Lily is a frog. It is certain that if 'John took the football' or 'Greg is a swan' or both then Jessica is a cat. There is a better than even chance that if either 'Greg is a swan' or 'Jeff dropped the apple' but not both then Bernhard is a swan.
hypothesis: Chances are about even that 'Bernhard is a swan' or 'Lily is a frog' or both.
valid_hypothesis: Chances are about even that 'Bernhard is a swan' or 'Lily is a frog' or both.
invalid_hypothesis: It is certain that 'Bernhard is a swan' or 'Lily is a frog' 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
    0.7::factA.
    0.2::factB.
    0.2::factC.
    %hop1
    0.6::factX:-and(factA,factB).
    1.0::factY:-or(factC,factA).
    0.6::factZ:-xor(factA,factB).
  
    %hop2
    conclusion:-or(factZ,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a swan' or 'Lily is a frog' or both.