Young boys playing ball on the beach.
The children are playing.
"Young boys playing ball" is a rephrasing of "children are playing"
exists e1 s1 x1 x2 x3 x4.(n_beach(x4) & a_topic(x1) & on(e1,x4) & Theme(e1,x3) & Actor(e1,x2) & v_play(e1) & n_ball(x3) & (x1 = x2) & n_boy(x1) & a_young(s1) & Theme(s1,x1))
exists e1 x1.(n_child(x1) & Actor(e1,x1) & v_play(e1))