Monday, 10 October 2011

Completeness of policy refinement

Source: N. Damianou, A. Bandara, M. Sloman, and E. Lupu. A Survey of Policy Specification Approaches. Technical re- port, Department of Computing, Imperial College of Science Technology and Medicine, London, 2002.

The objective of policy refinement is to transform high-level policy specifications into more specific policies that would be better suited for use in different execution environments.

Definition: (Policy Refinement) If there exists a set of policies Prs:p1, p2, .. pn, such that the enforcement of a combination of these policies results in a system behaving in an identical manner to a system that is enforcing some base policy Pb, it can be said that Prs is a refinement of Pb. The set of policies Prs:p1, p2, .. pn is referred to as the refined policy set.

A policy refinement can be said to complete iff all the following properties hold:
1.    Correctness: a refinement is said to be correct if there exists a subset of the refined policy set such that the conjunction of all the members of that subset is also a refinement of the base policy.
2.    Consistency: refinement is said to be consistent if there are no conflicts between any of the policies in the refined policy set.
3.    Minimality: a refinement is said to be minimal if it is correct and if removing any policy from the refined policy set causes the refinement to be incorrect.


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