A group of people are at a rock concert.
A group of people are swimming,
being and swimming are two different actions
exists p1 x1 x2.(exists x3 x4.(at(x1,x3) & n_concert(x3) & of(x3,x4) & n_rock(x4)) & of(x1,x2) & n_people(x2) & n_group(x1))
exists p1 x1 x2.(exists x3.((x1 = x3) & n_swimming(x3)) & of(x1,x2) & n_people(x2) & n_group(x1))