This group of boys are fishing off of a bridge.
Boys are playing on a bridge.
Boys aren't always playing.
exists e1 x1 x2 x3.(n_group(x1) & of(e1,x3) & n_bridge(x3) & r_off(e1) & Actor(e1,x1) & v_fish(e1) & of(x1,x2) & n_boy(x2))
exists e1 x1 x2.(on(e1,x2) & n_bridge(x2) & Actor(e1,x1) & v_play(e1) & n_boy(x1))