A guy skateboarding on the side of steps.
The guy is riding a bike.
Skateboarding versus riding.
exists e1 x1 x2 x3 x4.(n_side(x3) & a_topic(x1) & on(e1,x3) & of(x3,x4) & n_step(x4) & Actor(e1,x2) & v_skateboard(e1) & (x1 = x2) & n_guy(x1))
exists e1 x1 x2.(n_guy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2))