"FIG. 7A is a vertical cross sectional view of the affinity domain for City A in FIG. 5, in a plane through the locations of the importance values for City A and City H. In FIG. 7A, the importance value for City H is shown to exceed the affinity value domain for City A. Thus, City H is important enough to occupy a position at the same index level as City A. FIG. 7B is a vertical cross sectional vie" . . . .