Presentation of the paper: Evaluating role mining algorithms. In Proceedings of the 14th ACM symposium on Access control models and technologies (SACMAT '09) Ian Molloy, Ninghui Li, Tiancheng Li, Ziqing Mao, Qihua Wang, and Jorge Lobo. 2009. ACM, New York, NY, USA, 95-104. DOI=10.1145/1542207.1542224 http://doi.acm.org/10.1145/1542207.1542224

1. Evaluating Role Mining
Algorithms
SACMAT’09, June 3 - 5, 2009, Stresa, Italy.
Ian Molloy, Ninghui Li, Tiancheng Li, Ziqing Mao, Qihua Wang
@ CERIAS Research Center Department of Computer Science, Purdue University
Jorge Lobo @ IBM T.J. Watson Research Center
Presentation by Onur Yılmaz - onur@onuryilmaz.me

2. Outline
 Introduction
 Overview
 Role Mining Algorithms
 Evaluation Results
 Analysis
 Conclusion
 Future Work

3. Introduction
 Aim of the study
 Comprehensive study to compare role mining algorithms
 What is presented?
 Two new methods for generating datasets
 Analysis of nine role mining algorithms

4. Introduction
Role Mining
 Using data mining techniques to discover roles from existing
system configuration data

5. Overview
 3 key points:
Output of a role mining algorithm
Criteria to compare outputs of algorithms
Input datasets

6. Overview
Output of Role Mining Algorithm
Existing algorithms based on their outputs:
 Class 1: Outputting prioritized roles
 Class 2: Outputting RBAC states

7. Overview
Output of Role Mining Algorithm
Class 1: Outputting prioritized roles
 Prioritized list of candidate roles, each of which is a set of permissions
 CompleteMiner and Fast-Miner
Candidate
role
generation
a set of candidate
roles from the userpermission assignment
data
Candidate
role
prioritization

8. Overview
Output of Role Mining Algorithm
Class 2: Outputting RBAC states
ρ = <User, Permission, UP >
RBAC state γ = <Roles, UserRoleAss,
RolePermissionAss,
RoleHierarchy, DirectUserPermissionAss>

9. Overview
Output of Role Mining Algorithm
Class 2: Outputting RBAC states
 Minimize some cost measure while finding RBAC
output
Number of roles, number of user assignments
etc..

10. Overview
Output of Role Mining Algorithm
Class 2: Outputting RBAC states
Weighted Structural Complexity (WSC)
Sums up the number of relationships in an RBAC state, with
possibly different weights for each relationship.

11. Overview
Output of Role Mining Algorithm
Class 2: Outputting RBAC states
Weighted Structural Complexity (WSC)
Given a weight vector W = < wr,
wu, wp, wh, wd >
wsc(γ,W) = wr ∗ |R| + wu ∗ |UA| + wp ∗ |PA|+
wh ∗ |transitive_reduce(RH)| + wd∗ |DUPA|

12. Overview
Output of Role Mining Algorithm
Class 2: Outputting RBAC states
Weighted Structural Complexity (WSC)
 Different weight vectors encode different mining objectives and
minimization goals
 HierarchicalMiner takes both a configuration ρ and a weight vector and
aims at outputting an RBAC state with low WSC.
 Graph optimization minimizes the number of edges

13. Overview
Output of Role Mining Algorithm
Class 1 vs Class 2 Algorithms
 RBAC states are easy to compare
 List of candidate roles can be more useful in practice
Administrator examines the role mining results and
determine whether to adopt some part of it.
In practice, whether role mining algorithms can suggest the
best candidate roles.

14. Overview
Metrics for Comparing Algorithms
Two metrics:
 Complexity of the RBAC state
 Quality of roles

15. Overview
Metrics for Comparing Algorithms
Complexity of the RBAC state
Using WSC, how well each algorithm performs
under a variety of mining objectives

16. Overview
Metrics for Comparing Algorithms
Quality of Roles
 For each weight vector W, evaluate the complexity of the optimal
RBAC state using only the top k roles.
 Among the top k roles, how quickly do the mined roles cover the UP
relation?
 Among the top k roles, how well do they «resemble» the original
roles?

17. Overview
Input Data Type
Access Control Configuration
ρ = <User, Permission, UserPermissionRelation >

18. Overview
Input Data Type
Datasets from literature

19. Overview
Input Data Type
 Generated Datasets
Random Data Generator
Tree-Based Data Generator
ERBAC Data Generator

20. Overview
Input Data Type
Random Data Generator
Permission
Role
User – Permission
Assignment
Roles
Number of Users,
Number of Roles,
Number of Permissions,
Users
Maximum Number of Roles for Users,
Maximum Number of Permissions for Role

21. Overview
Input Data Type
Tree-Based Data Generator
Assign
permissions to
nodes in the
tree
Assign users to
leaf nodes
Randomly
generate a tree
Number of Users,
Number of Permissions,
Height of Tree
Upper bound on number of children node,
Lower bound on number of children node

22. Overview
Input Data Type
ERBAC Data Generator
Permissions
Functional
Roles
Functional
Roles
Users
Number of Users,
Number of Business Roles,
Number of Functional Roles,
Number of Permissions
Business
Roles
Business
Roles
Maximum # of Business Roles,
Maximum # of Functional Roles,
Maximum # of Permissions

23. Role Mining Algorithms
Class 1
Class 2
CompleteMiner (CM)
ORCA
FastMiner (FM)
Graph Optimization (GO)
DynamicMiner (DM)
HP Role Minimization (HPr)
PairCount (PC)
HP Edge Minimization (HPe)
HierarchicalMiner (HM)

24. Role Mining Algorithms
CompleteMiner (CM)
Initial set of
roles
from user
permission sets
All possible
intersections
Prioritization
of roles
Candidate roles
Based on
number of
exact matches
Exponential Time

25. Role Mining Algorithms
FastMiner (FM)
Initial set of
roles
from user
permission sets
Only
intersection
between pairs of
initial roles
Prioritization of
roles
Candidate roles
O (n2m)
n: users, m: permissions

26. Role Mining Algorithms
DynamicMiner (DM)
 CM and FM -> static prioritization (does not consider candidate
roles that been already chosen)
Initial set of
roles
from user
permission sets
All possible
intersections
Prioritization
of roles
Candidate roles
with the highest
priority first
O (n * |C| * min{n,m} )
C: Set of candidate roles

27. Role Mining Algorithms
PairCount (PC)
 Newly proposed method
 CM -> Prioritization based on exact numbers
 In reality, multiple roles are assigned to a user
 Pair Count: Pairs of users that share the only role, but no other
PC(P) = | { (ui, uj ) | ui = uj ∧ P(ui) ∩ P(uj) = P } |
O (n2m)

28. Role Mining Algorithms
PairCount (PC)
Initial set of
roles
from user
permission sets
All possible
intersections
Prioritization
of roles
Candidate roles
Based on Pair
Counts
O (n2m)

29. Role Mining Algorithms
ORCA
 Hierarchical clustering on permissions
Set of clusters of
permissions
Find pairs of
clusters
The number
of users
having both
permissions is
the largest
Continue
until
One cluster
or
No user with
permissions in
two clusters
O (m2n)

30. Role Mining Algorithms
HP Role Minimization (HPr)
 Minimal set of roles to cover the user-permission assignment
relation
Selecting the
next user with
the fewest
uncovered
permissions
Select a user u and finds a
pair <U(u), P(u)>
All user-permission assignments between
U(u) and P(u) are removed
This pair forms a
«role»
P(u): Permissions of user u
U(u): All users have all the permissions of u
O (nm)

31. Role Mining Algorithms
HP Edge Minimization (HPe)
 Finding a RBAC state with minimal number of edges, called edge
concentration
 Similar to Graph Optimization algorithm, except this does not create a
role hierarchy
HPr
Greedily
improve
objective
function
If two roles have
overlap in the
permission or
user sets ->
restructuring
Converge
O (k2m)
k : number of iterations

32. Role Mining Algorithms
HierarchicalMiner (HM)
 Concept: < P, U > such that
 U contains all the users that have all permissions in P,
 P contains all the permissions that are shared by all users in U
Reduced
family of
concepts
Remove a role
if RBAC state
is improved
Removing a role:
- Redistribution of users
down the hierarchy
- Permissions up the
hierarchy
Heuristically
continue
Similar to Graph
Optimization but
uses concept
lattice.

33. Evaluation Results
 For each dataset, each algorithm
 Ranked according to their ability to optimize
evaluation criteria
 1 to N
 Two metrics mentioned before:
 Comparing Complexity of the RBAC States
 Comparing Prioritized Role Quality

34. Evaluation Results
Comparing Complexity of the RBAC States
 Role Minimization

35. Evaluation Results
Comparing Complexity of the RBAC States
 Edge Concentration
HM has an advantage in this test because its roles are designed for a role-hierarchy

36. Evaluation Results
Comparing Complexity of the RBAC States
 Allowed Noise at Direct Assignments
Dataset contains errors that should not be covered by roles.

37. Evaluation Results
Comparing Complexity of the RBAC States
 Discovering Original Roles
 Similarity of mined roles to original data
 Used metric is average maximal Jaccard
HM: The top 40+ roles
are more or less the ones
generated
PC: Performed the worst,
generating roles farthest
from the original data

38. Evaluation Results
Comparing Prioritized Role Quality
 Quality of WSC over k-roles

39. Evaluation Results
Comparing Prioritized Role Quality
 Quality of Coverage
How well the algorithm at quickly covering the UP relation?

40. Analysis
 Algorithms that minimize the number of roles often generate RBAC states
with a larger number of edges, resulting in increased complexity.
 GO generates large role hierarchies when the number of users is greater
than the number of permissions.
 DM is over-fitting some of the roles to cover users, and does not consider
the entire resulting RBAC state.
 HM is computationally and memory intensive.

41. Conclusion
 Aim of the study
 Comprehensive study to compare role mining algorithms
 What is presented?
 Two new methods for generating datasets
 Analysis of nine role mining algorithms

42. Future Work
 Handling data with attribute information
 In addition to the user-permission data, attribute
information may also be available.
 Handling noisy data
 In some scenarios, the input user-permission data
may contain noises.

43. Evaluating Role Mining
Algorithms
SACMAT’09, June 3 - 5, 2009, Stresa, Italy.
Ian Molloy, Ninghui Li, Tiancheng Li, Ziqing Mao, Qihua Wang
@ CERIAS Research Center Department of Computer Science, Purdue University
Jorge Lobo @ IBM T.J. Watson Research Center
Presentation by Onur Yılmaz - onur@onuryilmaz.me