context: It is probable that Julius is a frog. Chances are slight that Sandra took the apple. It is highly unlikely that Bernhard is green. It is improbable that if either 'Julius is a frog' or 'Sandra took the apple' but not both then Greg is yellow. It is likely that if 'Julius is a frog' or 'Sandra took the apple' or both then Jessica is a mouse. It is impossible that if either 'Sandra took the apple' or 'Bernhard is green' but not both then Brian is white.
hypothesis: There is a better than even chance that 'Greg is yellow' or 'Bernhard is green' or both.
valid_hypothesis: It is improbable that 'Greg is yellow' or 'Bernhard is green' or both.
invalid_hypothesis: There is a better than even chance that 'Greg is yellow' or 'Bernhard is green' 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
    0.7::factA.
    0.1::factB.
    0.05::factC.
    %hop1
    0.1::factX:-xor(factA,factB).
    0.7::factY:-or(factA,factB).
    0.0::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-or(factX,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is yellow' or 'Bernhard is green' or both.