A little boy walking on railroad tracks.
A little boy is by a train
Railroad tracks might not currently have a train on it
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x3) & n_track(x3) & of(x3,x4) & n_railroad(x4) & Actor(e1,x2) & v_walk(e1) & (x1 = x2) & n_boy(x1) & a_little(s1) & Theme(s1,x1))
exists p1 s1 x1.(exists x2.(by(x1,x2) & n_train(x2)) & n_boy(x1) & a_little(s1) & Theme(s1,x1))