A computer network has storage devices organized into X levels and storing element-group information. To determine whether an element is a member of any target groups, each target group is validated by searching the storage devices to find a target group item and, if found, placing the target group in a validated target bin (V). Also, the element is validated by searching the storage devices to find an element item, and if found, determining from the item all groups that the element is listed as being a member of and placing such member-of groups in a search bin (S). If (S) intersects (V), the element is a member of a target group. If not, all groups in (S) are moved to a queue (Q1) corresponding to the storage device at level 1 and an iterative process searches for a membership path from the element to any target group.