A child on a rock in a stream.
The child is swimming.
One cannot be on a rock and swimming at the same time.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & in(x2,x3) & n_stream(x3) & n_rock(x2) & n_child(x1))
exists p1 x1.(n_child(x1) & exists x2.((x1 = x2) & n_swimming(x2)))