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Ontology & Rule-based Policies: A Hybrid Approach for Control Agents in Pervasive Environments

This paper explores a hybrid approach that combines ontology-based and rule-based policies for controlling agents in pervasive environments. It discusses the benefits and limitations of both approaches and proposes a hybrid approach that leverages the expressivity of ontologies and the executability of rules.

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Ontology & Rule-based Policies: A Hybrid Approach for Control Agents in Pervasive Environments

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

  2. Ruling Resource Access in a Pervasive Scenario 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. SWPW – Galway – November 7, 2005

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

  4. The Printer Access Policy in the KAoS Framework <owl:Class rdf:ID=”SkyTeamGate31-57PrinterAccessAction”> <owl:intersectionOf rdf:parseType=“Collection”/> <owl:Class rdf:about=“&action;AccessAction”/> <owl:Restriction> <owl:onProperty rdf:resource=”&action;performedBy”/> <owl:allValuesFrom rdf:resource=”#SkyTeamCustomer”/> </owl:Restriction> <owl:Restriction> <owl:onProperty rdf:resource=”&action;accessedEntity”/> <owl:allValuesFrom rdf:resource=”#Printer31-57”/> </owl:Restriction> </owl:intersectionOf> </owl:Class> < policy:PosAuthorizationPolicy rdf:ID=” SkyTeamGate31-57PrinterAccess”> < policy:controls rdf:resource=”# SkyTeamGate31-57PrinterAccessAction”/> <policy:hasSiteOfEnforcement rdf:resource=”&some-ontology;TargetSite”/> <policy:hasPriority>10</policy:hasPriority> </policy:PosAutihorizationPolicy> <owl:Class rdf:ID=”SkyTeamCustomer”> <rdfs:subClassOf rdf:resource=”&some-ontology;Customer”/> <rdfs:subClassOf> <owl:Restriction> <owl:onProperty rdf:resource=”&some-ontology;firm”/> <owl:allValuesFrom rdf:resource=”&some-ontology;SkyTeamAlliance”/> </owl:Restriction> </rdfs:subClassOf> <owl:Class> Context conditions are defined by restrictions over the action ontology properties Contexts and policies are expressed as ontologies SWPW – Galway – November 7, 2005

  5. KAoS (2) • 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 SWPW – Galway – November 7, 2005

  6. The Location Sharing Policy in the Rei Framework 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 SWPW – Galway – November 7, 2005

  7. Rei (2) • 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 SWPW – Galway – November 7, 2005

  8. Toward a Hybrid Approach? Ontology-based approach Rule-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 SWPW – Galway – November 7, 2005

  9. What a Hybrid Approach For? 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 SWPW – Galway – November 7, 2005

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

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