A rollerskater does tricks on a half pipe.
A rollerskater does a trick without rollerskates.
He is either doing one trick, or multiple tricks.
exists e1 x1 x2 x3 x4.(on(e1,x3) & n_pipe(x3) & of(x3,x4) & n_half(x4) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_trick(x2) & n_rollerskater(x1))
exists e1 x1 x2.(-exists x3.(with(e1,x3) & n_rollerskate(x3)) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_trick(x2) & n_rollerskater(x1))