An Ontological Implementation of a RoleBased Access Control Policy for Health
Care Information
Cristian Cocos and Wendy MacCaull
({ccocos,wmaccaul}@stfx.ca)
Centre for Logic and Information
St. Francis Xavier University, Nova Scotia
Canada
1
Introduction
• Currently developing a workflow
management system for community-based
palliative and seniors’ care
• Scheduled to be deployed at several
hospitals in rural Nova Scotia
• The aim: streamlining workflow by
improving process documentation and
communication
• Collaborative project involving healthcare
entities
2
Ontological RBAC
Introduction
• Perils: security and privacy
• Idea: use ontological structures to
represent access control policies
• More exactly: use the classes of an
ontology to model roles, and role hierarchy
• Adopt a suitable upper-level ontology: our
choice was BFO
• Other concerns: re-use portions of existing
ontologies: SNOMED-CT, ICNP etc.
3
Ontological RBAC
Access control scenario
• Two types of resources in need of access
control
– Informational items
– System actions
• E.g.: database fields (patient ID, patient
name, primary diagnosis etc.) and, resp.,
actions such as form/report printing,
faxing, phoning, appointment scheduling
etc.
4
Ontological RBAC
Access control policy
• Roles are organized hierarchically
• Resources are organized hierarchically
• Constraints can be provided for each form
field and action individually
• Allows for disjoint roles
• Database fields can be accessed as both
read only and write
• System users may have multiple roles with
regard to the same patient
5
Ontological RBAC
Implementation
• BFO
6
Ontological RBAC
Implementation
• BFO:role branch contains the main
mechanism
• Most of the classes that populate this
branch have been imported from
SNOMED-CT
7
Ontological RBAC
Implementation
• Core ACO mechanisms reside under the
Clearance-Level0Role and
PermissionLevel0Role:
8
Ontological RBAC
Implementation
• ClearanceLevelRole classes are defined
as a union of roles that have a certain
security clearance level
• Similar story goes for
PermissionLevelRole classes
Ontological RBAC
9
Implementation
• All ClearanceLevelyRole roles have also
clearance level x for x  y, but not viceversa
• E.g., all information that is accessible to a
community nurse (say) is also accessible
to a clinical oncologist (a
ClearanceLevel0Role role)
10
Ontological RBAC
Implementation
• Relations required to tie clearance and
permission level roles with database fields
and system actions respectively
• hasWriteAccessTo and hasReadAccessTo
• writeAccessibleBy and readAccessibleBy
• invokableBy (for actions)
• hasRole/roleOf
• hasClearanceLevel/clearanceLevelOf
• permissionLevelOf
11
Ontological RBAC
Implementation
• Classes that represent controlled
information are children of the
BFO:generically_dependent_continuant
12
Ontological RBAC
Implementation
• Classes that represent controlled actions
comprise the ACO:SystemProcedure
class, which is a child of BFO:process
13
Ontological RBAC
Implementation
• All classes that make the subject of
access control have restrictions outlining
their clearance/permission level
14
Ontological RBAC
Implementation
• Finally, the last of the relevant BFO
classes is BFO:object, that contains
SNOMED’s “Homo sapiens (organism),”
which represents the main ACO rolebearer
• ACO expressivity: SROIF
15
Ontological RBAC
Workflow interaction
• Access control clearance is checked at
login time, by querying ACO upon user
login
• The query returns a list of GASHA form
fields and reports whose access is
forbidden to the user, and a list of system
actions permitted
• The workflow system acts accordingly, by
blocking access to the requisite actions
and information entities
16
Ontological RBAC
Workflow interaction
• Query examples (ALCHO DL):
• not (accessibleBy some (roleOf value
Individual1)); this reveals all the form fields
that are not accessible to Individual1
• invokableBy some (roleOf value
Individual2) returns all system actions that
Individual2 has permission to launch
17
Ontological RBAC
Workflow interaction
• The workflow system also uses a
knowledge base for actual palliative and
seniors’ care knowledge
• Also in ontology format (PCSO)
• PCSO will provide logic-based guidance
for the workflow at the decision points
• Decision points = points in the workflow
where it branches, and where palliative
and seniors’ care knowledge is involved in
the decision
18
Ontological RBAC
Workflow interaction
• PCSO interaction scenario:
• the workflow reaches a decision point
• PCSO is queried with the patient data
contained in the EHR, and furnishes
information regarding the workflow branch
that the process is recommended to follow
for that particular patient
19
Ontological RBAC
Workflow interaction
• PCSO interaction scenario (cont’d):
• The information returned by the query is
analyzed by the responsible physician
• Physician ultimately decides whether the
process should follows the path indicated
by the ontology query
20
Ontological RBAC
Future work for ACO
• Add a customization phase
• Requires implementing a workflow
mechanism that queries the patient/client on
specific access control preferences during
several predetermined phases of the
workflow
• Also implement a workflow mechanism that
builds new patient-specific access control
ontologies that will be combined with the
default ACO described above in order to
customize the access control policy for each
patient
21
Ontological RBAC
Future work for ACO
• Implement an emergency override
scenario (“break the glass” mechanism)
• Question: can this be implemented using a
DL-based ontology?
22
Ontological RBAC
References
•
•
•
•
•
•
•
Bittner, T. and Smith, B. (2004) Normalizing Medical Ontologies using Basic Formal
Ontology, in Kooperative Versorgung, Vernetzte Forschung, Ubiquitäre Information
(Proceedings of GMDS Innsbruck, 26-30 September 2004), Niebüll: Videel OHG, pp. 199–
201.
Bouamrane, M.-M., Rector A. and Hurrell, M. (2009) A Hybrid Architecture for a
Preoperative Decision Support System Using a Rule Engine and a Reasoner on a Clinical
Ontology, in Polleres, A. and Swift, T. (Eds.): RR 2009, LNCS 5837, pp. 242–253,
Springer-Verlag Berlin Heidelberg 2009.
Finin, T. et al. (2008), ROWLBAC - Representing Role Based Access Control in OWL, in
SACMAT’08, June 11–13, 2008, Estes Park, Colorado, USA.
Grenon, P., Smith, B. and Goldberg, L. (2004) Biodynamic Ontology: Applying BFO in the
Biomedical Domain. In D. M. Pisanelli (ed.), Ontologies in Medicine, Amsterdam: IOS
Press, 2004, pp. 20–38.
Miller, K. and MacCaull, W. (2009) Toward Web-based Careflow Management Systems,
Journal of Emerging Techniologies in Web Intelligence, vol. 1, no. 2, pp. 137-145.
Tsoumas, B., Dritsas, S. and Gritzalis, D. (2005) An Ontology-Based Approach to
Information Systems Security Management in V. Gorodetsky et al. (eds.): MMM-ACNS
2005, LNCS 3685, Springer-Verlag Berlin Heidelberg, pp. 151 – 164, 2005.
Kazakov, Y. (2008) SRIQ and SROIQ are Harder than SHOIQ, in Baader, F. et al. (eds.),
DL 2008. Vol. 353 of CEUR Workshop Proceedings.
23
Ontological RBAC