context: It is impossible that Julius is gray. We doubt that Brian is white. There is almost no chance that Emily is a cat. It is probable that if either 'Brian is white' or 'Emily is a cat' but not both then Greg is a rhino. It is certain that if 'Julius is gray' or 'Emily is a cat' or both then John dropped the milk. It is likely that if 'Brian is white and Julius is gray' then Sandra put down the milk.
hypothesis: Chances are slight that 'Greg is a rhino' or 'Sandra put down the milk' or both.
valid_hypothesis: Chances are slight that 'Greg is a rhino' or 'Sandra put down the milk' or both.
invalid_hypothesis: It is likely that 'Greg is a rhino' or 'Sandra put down the milk' 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
    0.0::factA.
    0.2::factB.
    0.02::factC.
    %hop1
    0.7::factX:-xor(factB,factC).
    1.0::factY:-or(factA,factC).
    0.7::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-or(factX,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a rhino' or 'Sandra put down the milk' or both.