The skateboarder is wearing a helmet.
A skateboarder is wearing a baseball cap.
There can either be a helmet or baseball cap.
exists e1 x1 x2.(n_skateboarder(x1) & Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_helmet(x2))
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_cap(x2) & of(x2,x3) & n_baseball(x3) & n_skateboarder(x1))