A dog walking on a beach
a dog walks the beach alone
The dog could be walking alone, or with other dogs, or with a person or people.
exists x1 x2 x3.(a_topic(x1) & on(x1,x3) & n_beach(x3) & n_walking(x1) & of(x1,x2) & n_dog(x2))
exists e1 x1 x2.(n_beach(x2) & Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & r_alone(x2) & n_dog(x1))