A band is performing on stage.
There is a concert today.
band doesn't always mean  concert
exists e1 x1 x2.(on(e1,x2) & n_stage(x2) & Actor(e1,x1) & v_perform(e1) & n_band(x1))
exists p1 x1 x2.(Time(p1,x2) & n_today(x2) & exists x3.((x1 = x3) & n_concert(x3)))