A boy watches another person falling in the snow.
Boy throwing snow balls.
The boy is either watches or throwing, can not be doing both at once. There may or may not be another person present we don't know.
exists e1 e2 x1 x2 x3 x4 x5.(n_snow(x5) & n_person(x2) & Theme(e2,x3) & Actor(e2,x1) & v_watch(e2) & in(e1,x5) & Actor(e1,x4) & v_fall(e1) & (x3 = x4) & n_person(x3) & -(x3 = x2) & n_boy(x1))
exists e1 x1 x2 x3.(ne_nam_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_throw(e1) & n_ball(x2) & of(x2,x3) & n_snow(x3))