Ontology-based and Rule-based Policies: Toward a Hybrid Approach to Control Agents in Pervasive Environments The Semantic Web and Policy Workshop – ISWC Galway, November 7, 2005 Jeffrey M. Bradshaw Institute for Human and Machine Cognition Pensacola, Florida – USA Alessandra Toninelli, Rebecca Montanari Department of Electronics, Computer Science and Systems University of Bologna – Italy {atoninelli, Lalana Kagal MIT CSAIL Boston – USA

Ruling Resource Access in a Pervasive Scenario SWPW – Galway – November 7, 2005 LocationSharing Policy Users that are currently co-located with the owner of the resource, i.e., with her device, are authorized to access the shared files stored on the owner device. PrinterAccess Policy Travellers that are flying with a company of the Sky Team group, and are currently located in the airport area including gate from 31 to 57 are authorized to access the printer.

Context in Policy Frameworks SWPW – Galway – November 7, 2005 Policy Specification Requirements: In pervasive environments policies should be: context-based context-sensitive context representation context-based permitted and/or obliged actions context-based policy adaptation  At a high level of abstraction  In an interoperable format

10 The Printer Access Policy in the KAoS Framework SWPW – Galway – November 7, 2005 Contexts and policies are expressed as ontologies Context conditions are defined by restrictions over the action ontology properties

KAoS (2) SWPW – Galway – November 7, 2005 KAoS adopts an ontology-based approach: Classification of policies and contexts Reasoning (subsumption) over policy and context domain Static conflict detection  No variables  No parametric constraints KAoS extension: role-value maps

The Location Sharing Policy in the Rei Framework SWPW – Galway – November 7, A policy consists of a list of rules and a context Constraints are defined by means of a logic-like pattern Context conditions are expressed as constraints

Rei (2) SWPW – Galway – November 7, 2005 Rei adopts a rule-based approach: Greater expressivity (variables, parametric constraints) Rules are concise and human-readable Rules are “executable” (easier enforcement mechanism)  No reasoning over policy ontologies (e.g., policy classification)  Separate reasoning over domain knowledge (virtual fact base)  No static conflict detection

Toward a Hybrid Approach? SWPW – Galway – November 7, 2005 Ontology-based approachRule-based approach - KAoS has adopted role-value maps extensions to overcome OWL (DL) limitations - Rei has moved to OWL-Lite syntax to enable extensibility and domain knowledge integration

What a Hybrid Approach For? SWPW – Galway – November 7, 2005 A hybrid approach for Context-Sensitivity - Ontologies may allow a uniform and expressive modeling of context and policies - Ontologies may facilitate integration with existing/new context knowledge - Rules may allow to specify the behavior of policies in response to context changes

Thank you SWPW – Galway – November 7, 2005 Question time...