A seminar in an auditorium.
A seminar on a beach in the water.
The seminar is in an auditorium not a beach.
exists x1 x2.(a_topic(x1) & in(x1,x2) & n_auditorium(x2) & n_seminar(x1))
exists x1 x2 x3.(n_water(x3) & a_topic(x1) & on(x1,x2) & in(x2,x3) & n_beach(x2) & n_seminar(x1))