A boy in a red shirt sledding down a sand dune.
The little boy is trying to set the world speed record in sand dune sledding.
This implies that the boy is going very fast.  The boy in the first sentence doesn't necessarily have to be going fast.
exists e1 s1 s2 x1 x2 x3 x4 x5.(a_topic(x1) & in(x1,x2) & a_down(s2) & Manner(e1,s2) & Theme(e1,x4) & Actor(e1,x3) & v_sled(e1) & n_dune(x4) & of(x4,x5) & n_sand(x5) & (x2 = x3) & n_shirt(x2) & a_red(s1) & Theme(s1,x2) & n_boy(x1))
exists e1 p1 s1 x1 x2 x3 x4.(n_record(x2) & of(x2,x4) & n_speed(x4) & of(x2,x3) & n_world(x3) & n_boy(x1) & a_little(s1) & Theme(s1,x1) & Topic(e1,p1) & Actor(e1,x1) & v_try(e1) & exists e2 x5 x6 x7.(Theme(e2,x2) & Actor(e2,x1) & v_set(e2) & in(x2,x5) & n_sledding(x5) & of(x5,x7) & n_dune(x7) & of(x5,x6) & n_sand(x6)))