People are gathered at a business conference.
No body is using the conference room.
If there are people, it means that there cannot be no body present.
exists e1 x1 x2 x3.(at(e1,x2) & n_conference(x2) & of(x2,x3) & n_business(x3) & Theme(e1,x1) & v_gather(e1) & n_people(x1))
exists x2 x3.(n_room(x2) & of(x2,x3) & n_conference(x3) & -exists e1 x1.(Theme(e1,x2) & Actor(e1,x1) & v_use(e1) & n_body(x1)))