context: There is a very good chance that Jessica is a cat. We believe that John dropped the apple. There is a very good chance that Greg is a swan. It is probably not the case that if 'John dropped the apple and Jessica is a cat' then Bernhard is gray. Chances are slight that if 'Jessica is a cat' or 'John dropped the apple' or both then Fred went to the garden. It is probably the case that if 'Greg is a swan' or 'Jessica is a cat' or both then Brian is white.
hypothesis: Chances are slight that 'Greg is a swan and Brian is white'.
valid_hypothesis: There is a better than even chance that 'Greg is a swan and Brian is white'.
invalid_hypothesis: Chances are slight that 'Greg is a swan and Brian 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
    0.8::factA.
    0.75::factB.
    0.8::factC.
    %hop1
    0.25::factX:-and(factB,factA).
    0.1::factY:-or(factA,factB).
    0.7::factZ:-or(factC,factA).
  
    %hop2
    conclusion:-and(factC,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and Brian is white'.