16. A method according to claim 11 , further comprising: generating groups of the cluster spines, comprising: selecting those cluster spines that are unique; grafting one or more remaining cluster spines on one such unique cluster spine as one such cluster spine group.
17. A method according to claim 16 , further comprising: placing the cluster spine groups within the two-dimensional display by arranging one or more of the cluster spine groups circumferentially to a circle defined within the two-dimensional display.