People attending an event in a park.
An empty park.
If people are in a park, the park can not be empty.
exists e1 x1 x2 x3 x4.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_attend(e1) & in(x3,x4) & n_park(x4) & n_event(x3) & (x1 = x2) & n_people(x1))
exists s1 x1.(a_topic(x1) & n_park(x1) & a_empty(s1) & Theme(s1,x1))