A person in a hat is skateboarding and there is graffiti behind them.
The man is wearing knee pads.
Not all people skateboarding is wearing knee pads.
exists e1 p1 x1 x2 x3.(exists x4.((x3 = x4) & behind(x4,x1) & n_graffitus(x4)) & n_thing(x1) & Actor(e1,x1) & v_skateboard(e1) & in(x1,x2) & n_hat(x2) & n_person(x1))
exists e1 x1 x2 x3.(n_man(x1) & Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_pad(x2) & of(x2,x3) & n_knee(x3))