One man who has a black backpack is approaching an escalator.
Someone with a backpack is approaching moving stairs.
man who has a black backpack is approaching an escalator simply means someone with a backpack is approaching moving stairs.
exists e2 e1 s1 x1 x2 x3 x4.(Theme(e2,x4) & Actor(e2,x1) & v_approach(e2) & n_escalator(x4) & Theme(e1,x3) & Actor(e1,x2) & v_have(e1) & n_backpack(x3) & a_black(s1) & Theme(s1,x3) & (x1 = x2) & n_man(x1) & card_eq_1(x1))
exists e2 e1 x1 x2 x3.(Theme(e2,x3) & Actor(e2,x1) & v_approach(e2) & n_stair(x3) & Actor(e1,x3) & v_move(e1) & with(x1,x2) & n_backpack(x2) & n_person(x1))