A man standing on a locomotive working on it.
the man is a mechanic
Working on a locomotive implies he is a mechanic
exists e1 e2 x1 x2 x3.(a_topic(x1) & for(e1,e2) & on(e2,x1) & n_thing(x1) & Actor(e2,x2) & v_working(e2) & on(e1,x3) & n_locomotive(x3) & Actor(e1,x2) & v_stand(e1) & (x1 = x2) & n_man(x1))
exists p1 x1.(n_man(x1) & exists x2.((x1 = x2) & n_mechanic(x2)))