11. A computer-implemented method for cluster spine group arrangement, comprising: obtaining a set of spine groups each comprising one or more spines of clusters and at least one singleton cluster; identifying unique spine groups within the set; placing the unique spine groups in a center of a display; and placing at least a portion of the remaining spine groups in the set extending radially from the unique spine groups in the display center.
15. A method according to claim 11 , further comprising: generating one such spine group, comprising: arranging two or more clusters of documents along a spine based on concepts of the clusters; and grafting at least one other spine of clusters to one of the clusters arranged along the spine.