a group of people walking down the street.
A pickle riding a cat.
A pickle and cat do not constitute a group of people. One cannot walk while riding something.
exists e1 x1 x2 x3 x4.(n_street(x4) & a_topic(x1) & of(x1,x2) & down(e1,x4) & Actor(e1,x3) & v_walk(e1) & (x2 = x3) & n_people(x2) & n_group(x1))
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_cat(x3) & (x1 = x2) & n_pickle(x1))