Three workers are working on a metal roof
People are looking at a building.
People are not necessarily workers. One working on a roof is not looking at a building.
exists e1 x1 x2 x3.(on(e1,x2) & n_roof(x2) & of(x2,x3) & n_metal(x3) & Actor(e1,x1) & v_work(e1) & n_worker(x1) & card_eq_3(x1))
exists e1 x1 x2.(at(e1,x2) & n_building(x2) & Actor(e1,x1) & v_look(e1) & n_people(x1))