A skateboarder sits on a bench while wearing a black helmet.
A skateboarder is waiting for his friends to join him.
The skateboarder sitting on the bench is not necessarily waiting for his friends to join him as he could be skateboarding alone.
exists e1 e2 s1 x1 x2 x3.(while(e1,e2) & Theme(e2,x3) & Actor(e2,x1) & v_wear(e2) & n_helmet(x3) & a_black(s1) & Theme(s1,x3) & on(e1,x2) & n_bench(x2) & Actor(e1,x1) & v_sit(e1) & n_skateboarder(x1))
exists e1 p1 x1 x2 x3.(Topic(e1,p1) & exists e2.(Theme(e2,x2) & Actor(e2,x1) & v_join(e2)) & n_male(x2) & for(e1,x3) & n_friend(x3) & of(x3,x1) & n_male(x1) & Actor(e1,x2) & v_wait(e1) & n_skateboarder(x2) & n_skateboarder(x1))