context: It is probably not the case that Bernhard is yellow. We doubt that Brian is white. It is highly likely that Gertrude is a mouse. It is certain that if either 'Bernhard is yellow' or 'Gertrude is a mouse' but not both then Mary dropped the apple. It is probable that if 'Brian is white' or 'Bernhard is yellow' or both then Greg is a rhino. It is likely that if either 'Bernhard is yellow' or 'Gertrude is a mouse' but not both then Julius is gray.
hypothesis: Chances are about even that 'Bernhard is yellow' or 'Brian is white' or both.
valid_hypothesis: Chances are about even that 'Bernhard is yellow' or 'Brian is white' or both.
invalid_hypothesis: It is impossible that 'Bernhard is yellow' 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
    0.25::factA.
    0.2::factB.
    0.9::factC.
    %hop1
    1.0::factX:-xor(factA,factC).
    0.7::factY:-or(factB,factA).
    0.7::factZ:-xor(factA,factC).
  
    %hop2
    conclusion:-or(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is yellow' or 'Brian is white' or both.