context: It is highly likely that Emily is a sheep. There is little chance that Greg is a lion. It is certain that Lily is green. There is almost no chance that if either 'Emily is a sheep' or 'Greg is a lion' but not both then Bernhard is a frog. It is probably the case that if either 'Emily is a sheep' or 'Greg is a lion' but not both then Brian is yellow. Chances are about even that if either 'Greg is a lion' or 'Lily is green' but not both then Daniel got the milk.
hypothesis: It is highly unlikely that 'Brian is yellow' or 'Bernhard is a frog' or both.
valid_hypothesis: There is a better than even chance that 'Brian is yellow' or 'Bernhard is a frog' or both.
invalid_hypothesis: It is highly unlikely that 'Brian is yellow' or 'Bernhard 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
    0.9::factA.
    0.1::factB.
    1.0::factC.
    %hop1
    0.02::factX:-xor(factA,factB).
    0.7::factY:-xor(factA,factB).
    0.5::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-or(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is yellow' or 'Bernhard is a frog' or both.