People laughing while at a restaurant.
People at a restaurant.
At a restaurant is a rephrasing of at a restaurant.
exists e1 x1 x2 x3.(a_topic(x1) & at(e1,x3) & n_restaurant(x3) & r_while(e1) & Actor(e1,x2) & v_laugh(e1) & (x1 = x2) & n_people(x1))
exists x1 x2.(a_topic(x1) & at(x1,x2) & n_restaurant(x2) & n_people(x1))