A crowd of people walking.
The people are standing.
The people were walking not standing
exists e1 x1 x2 x3.(a_topic(x1) & of(x1,x2) & Actor(e1,x3) & v_walk(e1) & (x2 = x3) & n_people(x2) & n_crowd(x1))
exists e1 x1.(n_people(x1) & Actor(e1,x1) & v_stand(e1))