A man in a green sweater sharping knifes on a sharping stone.
a stone is used to sharpen knives
If a person is sharpening knives on a sharpening stone, they are using the stone to sharpen the knives.
exists e1 s1 x1 x2 x3 x4 x5 x6.(a_topic(x1) & in(x1,x2) & on(e1,x5) & n_stone(x5) & of(x5,x6) & n_sharping(x6) & Theme(e1,x4) & Actor(e1,x3) & v_sharp(e1) & n_knife(x4) & (x2 = x3) & n_sweater(x2) & a_green(s1) & Theme(s1,x2) & n_man(x1))
exists e1 p1 x1.(Recipient(e1,p1) & Topic(e1,x1) & v_use(e1) & exists e2 x2.(Theme(e2,x2) & Actor(e2,x1) & v_sharpen(e2) & n_knife(x2)) & n_stone(x1))