A dog trotting down the beach with a toy in its mouth.
The dog is playing fetch with his owner.
We don't know that the dog is playing fetch or with his owner based on the first sentence.
exists e1 s1 x1 x2 x3 x4 x5.(n_mouth(x5) & of(x5,x3) & n_thing(x3) & n_beach(x3) & a_topic(x1) & with(e1,x4) & in(x4,x5) & n_toy(x4) & a_down(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x2) & v_trot(e1) & (x1 = x2) & n_dog(x1))
exists e1 x1 x2 x3.(n_owner(x3) & of(x3,x1) & n_male(x1) & n_dog(x1) & with(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_fetch(x2))