context: We believe that Greg is a frog. There is almost no chance that Jason is tired. It is improbable that Julius is a rhino. It is certain that if either 'Jason is tired' or 'Julius is a rhino' but not both then Gertrude is a mouse. There is a very good chance that if 'Julius is a rhino and Jason is tired' then John went to the garden. It is probable that if either 'Jason is tired' or 'Julius is a rhino' but not both then Sandra left the milk.
hypothesis: Chances are slight that 'Gertrude is a mouse and Julius is a rhino'.
valid_hypothesis: Chances are slight that 'Gertrude is a mouse and Julius is a rhino'.
invalid_hypothesis: There is a very good chance that 'Gertrude is a mouse and Julius is a rhino'.
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
    0.75::factA.
    0.02::factB.
    0.1::factC.
    %hop1
    1.0::factX:-xor(factB,factC).
    0.8::factY:-and(factC,factB).
    0.7::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-and(factX,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Gertrude is a mouse and Julius is a rhino'.