A classroom of students watching a presentation.
No one is in the room
If no one is in the room then there are no classroom of students.
exists e1 x1 x2 x3 x4.(a_topic(x1) & of(x1,x2) & Theme(e1,x4) & Actor(e1,x3) & v_watch(e1) & n_presentation(x4) & (x2 = x3) & n_student(x2) & n_classroom(x1))
exists x2.(n_room(x2) & -exists p1 x1.(in(x1,x2) & n_one(x1)))