context: Chances are about even that Lily is white. Chances are about even that Mary is in the bathroom. It is unlikely that Yann is hungry. We believe that if either 'Yann is hungry' or 'Mary is in the bathroom' but not both then Brian is a frog. There is little chance that if 'Yann is hungry' or 'Mary is in the bathroom' or both then Greg is yellow. It is probably the case that if either 'Mary is in the bathroom' or 'Yann is hungry' but not both then John went to the garden.
hypothesis: There is almost no chance that 'Greg is yellow and Lily is white'.
valid_hypothesis: There is almost no chance that 'Greg is yellow and Lily is white'.
invalid_hypothesis: There is a better than even chance that 'Greg is yellow 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
    0.5::factA.
    0.5::factB.
    0.2::factC.
    %hop1
    0.75::factX:-xor(factC,factB).
    0.1::factY:-or(factC,factB).
    0.7::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-and(factY,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is yellow and Lily is white'.