A woman on a cellphone taking a walk.
There is a woman.
There is a woman on a cellphone, walking. The later simply defines a key element to the statement.
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(x1,x2) & Theme(e1,x4) & Actor(e1,x3) & v_take(e1) & n_walk(x4) & (x2 = x3) & n_cellphone(x2) & n_woman(x1))
exists p1 x1 x2.((x1 = x2) & n_woman(x2))