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Recognizing immediacy in an N-tree hierarchy and its application to protection groups

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1 Author(s)
Sandhu, R.S. ; Dept. of Inf. Syst. & Syst. Eng., George Mason Univ., Fairfax, VA, USA

The benefits of providing access control with groups of users as the unit of granularity are enhanced if the groups are organized in a hierarchy (partial order) by the subgroup relation ⩽, where g h signifies that every member of group g is thereby also a member of group h. It is often useful to distinguish the case when g is an immediate subgroup of h , that is when g<h and there is no group k such that g<k<h. The class of partial orders called n-trees was recently defined by using rooted trees and inverted rooted trees as basic partial orders and combining these recursively by refinement. Any n-tree hierarchy can be expressed as the intersection of two linear orderings, so it is possible to assign a pair of integers l[x] and r [x] to each group x such that gh if and only if l[g]⩽l[h] and r[g ]⩽r[h]. The author shows how to extend this representation of n-trees by assigning four additional integers to each group so that it is also easily determined whether or not g is an immediate subgroup of h

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Software Engineering, IEEE Transactions on  (Volume:15 ,  Issue: 12 )