Children are pulling on a rope.
the children are playing
Children pulling on a rope are not necessarily playing.
exists e1 x1 x2.(on(e1,x2) & n_rope(x2) & Actor(e1,x1) & v_pull(e1) & n_child(x1))
exists e1 x1.(n_child(x1) & Actor(e1,x1) & v_play(e1))