A boy walks down the sidewalk with a trash bag while two other boys follow him.
A boy is chasing after the bag while his two friends try to catch up.
The boy isn't necessarily chasing after the bag. The other two boys might not be the first boy's friends. The other two boys also might not be trying to catch up.
exists e1 p1 s1 x1 x2 x3 x4.(n_male(x2) & n_sidewalk(x2) & exists e2 x5.(Theme(e2,x2) & Actor(e2,x5) & v_follow(e2) & -(x5 = x1) & n_boy(x5) & card_eq_2(x5)) & n_boy(x1) & n_boy(x1) & while(e1,p1) & a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_walk(e1) & with(x2,x3) & n_bag(x3) & of(x3,x4) & n_trash(x4))
exists e1 p1 x1 x2 x3.(n_friend(x3) & card_eq_2(x3) & of(x3,x2) & n_male(x2) & n_bag(x2) & exists e2 p2.(Topic(e2,p2) & Actor(e2,x3) & v_try(e2) & exists e3 s1.(a_up(s1) & Manner(e3,s1) & Actor(e3,x3) & v_catch(e3))) & while(e1,p1) & after(e1,x2) & Actor(e1,x1) & v_chase(e1) & n_boy(x1))