Black dog climbs over fallen logs or boards.
The black dog is chasing a fox.
Just because a black dog is climbing over fallen logs doesn't have to mean that it is chasing a fox.
exists s1 s2 x1 x2 x3.(a_topic(x1) & over(x1,x3) & (n_log(x3) | n_board(x3)) & a_fallen(s2) & Theme(s2,x3) & n_climb(x1) & of(x1,x2) & n_dog(x2) & a_black(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(n_dog(x1) & a_black(s1) & Theme(s1,x1) & Theme(e1,x2) & Actor(e1,x1) & v_chase(e1) & n_fox(x2))