A singer on a stage is singing into a microphone.
The person is a professional singer.
Not all singer on stage singing is a professional singer
exists e1 x1 x2 x3.(into(e1,x3) & n_microphone(x3) & Actor(e1,x1) & v_sing(e1) & on(x1,x2) & n_stage(x2) & n_singer(x1))
exists p1 x1.(n_person(x1) & exists s1 x2.((x1 = x2) & n_singer(x2) & a_professional(s1) & Theme(s1,x2)))