A gray dog runs along the green grass.
A gray dog runs after something in the green grass.
A dog can run for many reasons and not only if it is after something.
exists e1 s1 s2 x1 x2.(n_grass(x2) & a_green(s2) & Theme(s2,x2) & along(e1,x2) & Actor(e1,x1) & v_run(e1) & n_dog(x1) & a_gray(s1) & Theme(s1,x1))
exists s1 s2 x1 x2 x3 x4.(n_grass(x4) & a_green(s2) & Theme(s2,x4) & a_topic(x1) & after(x1,x3) & in(x3,x4) & n_thing(x3) & n_run(x1) & of(x1,x2) & n_dog(x2) & a_gray(s1) & Theme(s1,x1))