A young girl walks across big rocks.
The girl walks across slippery rocks.
the rocks may or may not be slippery.
exists e1 s1 s2 x1 x2.(across(e1,x2) & n_rock(x2) & a_big(s2) & Theme(s2,x2) & Actor(e1,x1) & v_walk(e1) & n_girl(x1) & a_young(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(n_girl(x1) & across(e1,x2) & n_rock(x2) & a_slippery(s1) & Theme(s1,x2) & Actor(e1,x1) & v_walk(e1))