A skateboarder performs a skateboard trick against a graffiti wall.
A skateboarder is sitting in his board.
A skateboarder performs a skateboard trick but it never happens if he is sitting in his board.
exists e1 x1 x2 x3 x4 x5.(against(e1,x4) & n_wall(x4) & of(x4,x5) & n_graffitus(x5) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_trick(x2) & of(x2,x3) & n_skateboard(x3) & n_skateboarder(x1))
exists e1 x1 x2.(in(e1,x2) & n_board(x2) & of(x2,x1) & n_male(x1) & Actor(e1,x1) & v_sit(e1) & n_skateboarder(x1))