Two men working on a tractor wearing hard hats.
Two construction workers are fixing the tractor.
Two men with hard hats are not necessarily construction workers and they may not be fixing the tractor.
exists e1 e2 s1 x1 x2 x3 x4 x5.(a_topic(x1) & on(e1,x3) & Theme(e2,x5) & Actor(e2,x4) & v_wear(e2) & n_hat(x5) & a_hard(s1) & Theme(s1,x5) & (x3 = x4) & n_tractor(x3) & Actor(e1,x2) & v_work(e1) & (x1 = x2) & n_man(x1) & card_eq_2(x1))
exists e1 x1 x2 x3.(n_tractor(x3) & Theme(e1,x3) & Actor(e1,x1) & v_fix(e1) & n_worker(x1) & of(x1,x2) & n_construction(x2) & card_eq_2(x1))