The boys play on the rocks overlooking the valley.
The boys play outside.
To play on the rocks implies being outside.
exists e2 e1 x1 x2 x3.(n_valley(x3) & n_rock(x2) & n_boy(x1) & for(e1,e2) & Theme(e2,x3) & Actor(e2,x1) & v_overlook(e2) & on(e1,x2) & Actor(e1,x1) & v_play(e1))
exists e1 s1 x1.(n_boy(x1) & a_outside(s1) & Manner(e1,s1) & Actor(e1,x1) & v_play(e1))