A group of skaters are at a skate park.
People are at a skate park.
Group usually means people.
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.(exists x2 x3.(at(x1,x2) & n_park(x2) & of(x2,x3) & n_skate(x3)) & n_people(x1))