12. A system according to claim 11 , further comprising: a group generator to generate one such spine group by identifying unique cluster spines from a set of cluster spines, selecting an anchor cluster on one of the unique cluster spines, selecting a cluster from one of the remaining cluster spines in the set that is most similar to the anchor cluster, and grafting the cluster of the remaining cluster spine to the anchor cluster of the unique cluster spine as the spine group.
12. A system according to claim 11 , further comprising: a group generator to generate one such spine group by identifying unique cluster spines from a set of cluster spines, selecting an anchor cluster on one of the unique cluster spines, selecting a cluster from one of the remaining cluster spines in the set that is most similar to the anchor cluster, and grafting the cluster of the remaining cluster spine to the anchor cluster of the unique cluster spine as the spine group. 13. A system according to claim 12 , further comprising: a unique determination module to determine that the spine groups are unique when each of the spine groups is sufficiently dissimilar to one another.