context: It is probably the case that Greg is white. Chances are slight that Jessica is a mouse. There is almost no chance that Julius is gray. There is little chance that if either 'Jessica is a mouse' or 'Julius is gray' but not both then Bernhard is a frog. Chances are about even that if either 'Julius is gray' or 'Greg is white' but not both then Lily is a swan. There is almost no chance that if either 'Jessica is a mouse' or 'Julius is gray' but not both then Brian is a rhino.
hypothesis: It is improbable that 'Greg is white' or 'Jessica is a mouse' or both.
valid_hypothesis: We believe that 'Greg is white' or 'Jessica is a mouse' or both.
invalid_hypothesis: It is improbable that 'Greg is white' or 'Jessica is a mouse' 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.
    0.02::factC.
    %hop1
    0.1::factX:-xor(factB,factC).
    0.5::factY:-xor(factC,factA).
    0.02::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-or(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is white' or 'Jessica is a mouse' or both.