context: There is a better than even chance that Gertrude is a sheep. It is highly unlikely that Julius is white. It is improbable that Bernhard is a frog. Chances are slight that if 'Bernhard is a frog' or 'Julius is white' or both then Mary moved to the garden. There is little chance that if 'Gertrude is a sheep' or 'Bernhard is a frog' or both then Daniel left the milk. It is highly likely that if either 'Bernhard is a frog' or 'Julius is white' but not both then Brian is a lion.
hypothesis: It is probably the case that 'Bernhard is a frog' or 'Julius is white' or both.
valid_hypothesis: Chances are slight that 'Bernhard is a frog' or 'Julius is white' or both.
invalid_hypothesis: It is probably the case that 'Bernhard is a frog' or 'Julius is white' 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.
    0.05::factB.
    0.1::factC.
    %hop1
    0.1::factX:-or(factC,factB).
    0.1::factY:-or(factA,factC).
    0.9::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-or(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a frog' or 'Julius is white' or both.