The dog stands on something while the snowfalls around him.
A dog is chasing a ball.
the dog doesn't stand on something while chasing a ball.
exists e1 x1 x2 x3.(n_male(x3) & n_snowfall(x3) & n_dog(x1) & around(e1,x3) & while(e1,x3) & on(e1,x2) & n_thing(x2) & Actor(e1,x1) & v_stand(e1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_chase(e1) & n_ball(x2) & n_dog(x1))