A boy is riding his bike over a ramp at a park.
A boy is skateboarding on the street.
One boy is riding his back while another boy is skateboarding.
exists e1 x1 x2 x3 x4.(at(e1,x4) & n_park(x4) & over(e1,x3) & n_ramp(x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & of(x2,x1) & n_male(x1) & n_boy(x1))
exists e1 x1 x2.(n_street(x2) & on(e1,x2) & Actor(e1,x1) & v_skateboard(e1) & n_boy(x1))