context: We believe that Sandra dropped the milk. Chances are about even that Lily is white. It is almost certain that Jessica is a cat. It is highly unlikely that if 'Lily is white' or 'Jessica is a cat' or both then Brian is white. There is almost no chance that if 'Lily is white' or 'Sandra dropped the milk' or both then Jeff moved to the office. We doubt that if 'Sandra dropped the milk' or 'Lily is white' or both then Mary went to the garden.
hypothesis: It is impossible that 'Lily is white' or 'Brian is white' or both.
valid_hypothesis: Chances are about even that 'Lily is white' or 'Brian is white' or both.
invalid_hypothesis: It is impossible that 'Lily is white' or 'Brian 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
    0.75::factA.
    0.5::factB.
    0.95::factC.
    %hop1
    0.05::factX:-or(factB,factC).
    0.02::factY:-or(factB,factA).
    0.2::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-or(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Lily is white' or 'Brian is white' or both.