A naked person standing on a rock.
A nudist stands on the rock.
Just because the person is naked on a rock doesn't imply they are a nudist, there's no way to know what they do at other times.
exists e1 s1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_rock(x3) & Actor(e1,x2) & v_stand(e1) & (x1 = x2) & n_person(x1) & a_naked(s1) & Theme(s1,x1))
exists s1 x1 x2.(n_rock(x2) & a_topic(x1) & on(x1,x2) & n_stand(x1) & a_nudist(s1) & Theme(s1,x1))