A shirtless man with a backpack.
the man is a model
A shirtless man is not necessarily a model.
exists s1 x1 x2.(a_topic(x1) & with(x1,x2) & n_backpack(x2) & n_man(x1) & a_shirtless(s1) & Theme(s1,x1))
exists p1 x1.(n_man(x1) & exists x2.((x1 = x2) & n_model(x2)))