context: Chances are slight that Julius is yellow. It is highly likely that Lily is white. There is little chance that Bernhard is a swan. It is probable that if either 'Julius is yellow' or 'Bernhard is a swan' but not both then Gertrude is a sheep. There is a very good chance that if 'Julius is yellow and Bernhard is a swan' then Brian is white. It is highly unlikely that if 'Lily is white and Julius is yellow' then John took the milk.
hypothesis: It is highly likely that 'Brian is white and Lily is white'.
valid_hypothesis: It is impossible that 'Brian is white and Lily is white'.
invalid_hypothesis: It is highly likely that 'Brian is white and Lily is white'.
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.
    0.9::factB.
    0.1::factC.
    %hop1
    0.7::factX:-xor(factA,factC).
    0.8::factY:-and(factA,factC).
    0.05::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-and(factY,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is white and Lily is white'.