A man is sitting in a chair playing guitar.
A man is performing onstage.
You can not infer he is onstage.
exists e1 e2 x1 x2 x3.(for(e1,e2) & Theme(e2,x3) & Actor(e2,x1) & v_play(e2) & n_guitar(x3) & in(e1,x2) & n_chair(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_onstage(x2) & n_man(x1))