A group of skaters are at a skate park.
There are some people skating.
Some people skating shows that there is a group of skaters.
exists p1 x1 x2.(exists x3 x4.(at(x1,x3) & n_park(x3) & of(x3,x4) & n_skate(x4)) & of(x1,x2) & n_skater(x2) & n_group(x1))
exists p1 x1 e1 x2 x3.((x1 = x2) & Actor(e1,x3) & v_skate(e1) & (x2 = x3) & n_people(x2))