A band performs on stage.
There is a band on the stage.
If the band performs on stage, it must be on the stage.
exists e1 x1 x2.(on(e1,x2) & n_stage(x2) & Actor(e1,x1) & v_perform(e1) & n_band(x1))
exists p1 x1 x3.(n_stage(x3) & exists x2.((x1 = x2) & on(x2,x3) & n_band(x2)))