A man is working on steel.
The man is working.
A man working on steel is working in general.
exists e1 x1 x2.(on(e1,x2) & n_steel(x2) & Actor(e1,x1) & v_work(e1) & n_man(x1))
exists e1 x1.(n_man(x1) & Actor(e1,x1) & v_work(e1))