Many people sit and socialize in groups inside a restaurant.
A group of friends are eating at a restaurant
People at a restaurant are not necessarily a group of friends.
exists e1 e2 x1 x2 x3 x4.(in(e2,x3) & inside(x3,x4) & n_restaurant(x4) & n_group(x3) & Actor(e2,x2) & v_socialize(e2) & n_people(x2) & n_quantity(x2) & Actor(e1,x1) & v_sit(e1) & n_people(x1) & n_quantity(x1))
exists e1 x1 x2 x3.(at(e1,x3) & n_restaurant(x3) & Actor(e1,x1) & v_eat(e1) & of(x1,x2) & n_friend(x2) & n_group(x1))