A person wearing a helmet begins to ride a skateboard down a street hill.
The person's arms are extended.
A skateboarders arms could be in any position.
exists e1 e2 p1 x1 x2 x3 x4 x5.(down(e2,x4) & n_hill(x4) & of(x4,x5) & n_street(x5) & Topic(e2,p1) & Actor(e2,x1) & v_begin(e2) & exists e3 x6.(Theme(e3,x6) & Actor(e3,x1) & v_ride(e3) & n_skateboard(x6)) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_helmet(x3) & (x1 = x2) & n_person(x1))
exists e1 x1 x2.(n_arm(x2) & of(x2,x1) & n_person(x1) & Theme(e1,x2) & v_extend(e1))