A group of motorcyclist are ridding through the streets.
They are a motorcycle gang.
Group of motorcyclist are not necessarily a gang.
exists e1 x1 x2 x3.(n_street(x3) & through(e1,x3) & Actor(e1,x1) & v_rid(e1) & of(x1,x2) & n_motorcyclist(x2) & n_group(x1))
exists p1 x1.(n_thing(x1) & exists x2 x3.((x1 = x2) & n_gang(x2) & of(x2,x3) & n_motorcycle(x3)))