The ball boys are waiting on the side lines of the tennis court while they watch the lady hitting the ball.
Ball boys eager await their chance to run on the court in front of the huge crowd.
Ball boys waiting does not imply that they are eager and await their change to run on the court.  A lady hitting the ball does not imply that they are in front of the huge crowd.
exists e1 p1 x1 x2 x3 x4 x5 x6 x7.(n_ball(x2) & n_ball(x2) & n_lady(x7) & n_thing(x3) & n_court(x5) & of(x5,x6) & n_tennis(x6) & n_line(x3) & of(x3,x4) & n_side(x4) & n_boy(x1) & of(x1,x2) & exists e3 e2 x8.(Theme(e3,x7) & Actor(e3,x3) & v_watch(e3) & Theme(e2,x2) & Actor(e2,x8) & v_hit(e2) & (x7 = x8)) & while(e1,p1) & on(e1,x3) & of(x3,x5) & Actor(e1,x1) & v_wait(e1))
exists e1 p1 s1 s2 x1 x2 x3 x4 x5 x6.(n_crowd(x5) & a_huge(s2) & Theme(s2,x5) & n_court(x6) & Theme(e1,x4) & Actor(e1,x1) & v_await(e1) & of(x4,x5) & Topic(x4,p1) & exists e2 x7.(in(e2,x7) & n_front(x7) & on(e2,x6) & Actor(e2,x4) & v_run(e2)) & n_chance(x4) & of(x4,x1) & n_thing(x1) & Theme(s1,x3) & a_eager(s1) & (x1 = x3) & n_boy(x1) & (x1 = x2) & ne_nam_ball(x2))