One boy hoists another boy up on his back.
A boy is giving another boy a piggyback ride.
Just because a boy hoists another boy doesn't necessarily mean he is giving him a piggyback ride
exists e1 s1 x1 x2 x3.(on(e1,x3) & n_back(x3) & of(x3,x2) & n_male(x2) & a_up(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_hoist(e1) & n_boy(x2) & -(x2 = x1) & n_boy(x1) & n_boy(x1) & card_eq_1(x1))
exists e1 x1 x2 x3 x4.(Recipient(e1,x4) & Theme(e1,x2) & Actor(e1,x1) & v_give(e1) & n_boy(x4) & -(x4 = x1) & n_boy(x1) & n_boy(x1) & n_ride(x2) & of(x2,x3) & n_piggyback(x3))