A crowd of people are in a street.
the people are rioters
People can be in the street without being rioters.
exists p1 x1 x2.(exists x3.(in(x1,x3) & n_street(x3)) & of(x1,x2) & n_people(x2) & n_crowd(x1))
exists p1 x1.(n_people(x1) & exists x2.((x1 = x2) & n_rioter(x2)))