A group of motorcyclists riding down the street.
There are people on motorcycles.
People, refers to the group of motorcyclists riding.
exists e1 x1 x2 x3 x4.(n_street(x4) & a_topic(x1) & down(e1,x4) & Actor(e1,x3) & v_ride(e1) & (x1 = x3) & of(x1,x2) & n_motorcyclist(x2) & n_group(x1))
exists p1 x1 x2 x3.((x1 = x2) & on(x2,x3) & n_motorcycle(x3) & n_people(x2))