Diapositiva 1

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_at_deis.unibo.it
Jeffrey M. Bradshaw Institute for Human and
Machine Cognition Pensacola, Florida
USA jbradshaw_at_ihmc.us
Lalana Kagal MIT CSAIL Boston USA
lkagal_at_csail.mit.edu
The Semantic Web and Policy Workshop ISWC 2005
- Galway, November 7, 2005
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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
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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 Specification Requirements
? At a high level of abstraction ? In an
interoperable format
SWPW Galway November 7, 2005
4
The Printer Access Policy in the KAoS Framework
ltowlClass rdfIDSkyTeamGate31-57PrinterAccessAc
tiongt ltowlintersectionOf
rdfparseTypeCollection/gt ltowlClass
rdfaboutactionAccessAction/gt
ltowlRestrictiongt ltowlonProperty
rdfresourceactionperformedBy/gt
ltowlallValuesFrom rdfresourceSkyTeamCustomer
/gt lt/owlRestrictiongt ltowlRestrictiongt
ltowlonProperty rdfresourceactionacces
sedEntity/gt ltowlallValuesFrom
rdfresourcePrinter31-57/gt
lt/owlRestrictiongt lt/owlintersectionOfgt lt/
owlClassgt lt policyPosAuthorizationPolicy
rdfID SkyTeamGate31-57PrinterAccessgt lt
policycontrols rdfresource
SkyTeamGate31-57PrinterAccessAction/gt
ltpolicyhasSiteOfEnforcement rdfresourcesome-o
ntologyTargetSite/gt ltpolicyhasPrioritygt10lt/p
olicyhasPrioritygt lt/policyPosAutihorizationPolic
ygt ltowlClass rdfIDSkyTeamCustomergt ltrdfssub
ClassOf rdfresourcesome-ontologyCustomer/gt
ltrdfssubClassOfgt ltowlRestrictiongt ltowlon
Property rdfresourcesome-ontologyfirm/gt ltow
lallValuesFrom rdfresourcesome-ontologySkyT
eamAlliance/gt lt/owlRestrictiongt
lt/rdfssubClassOfgt ltowlClassgt
Context conditions are defined by restrictions
over the action ontology properties
Contexts and policies are expressed as ontologies
SWPW Galway November 7, 2005
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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
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The Location Sharing Policy in the Rei Framework
ltpolicyPolicy rdfID"FileAccessPolicy"gt         ltpolicyactor rdfresource"requester"/gt         ltpolicygrants rdfresource"Perm_FileAccess"/gt lt/policyPolicygt ltpolicyPolicy rdfIDFileSharingPolicygt ... lt/policyPolicygt
ltconstraintSimpleConstraint rdfID"LocationOfUser"gt          ltconstraintsubject rdfresource"some-ontologyuser"/gt          ltconstraintpredicate rdfresource"some-ontologylocation"/gt          ltconstraintobject rdfresource"user-location"/gt lt/constraintSimpleConstraintgt ltconstraintSimpleConstraint rdfID"CoLocatedWithUser"gt          ltconstraintsubject rdfresource"requester"/gt          ltconstraintpredicate rdfresource"some-ontologylocation"/gt          ltconstraintobject rdfresource"user-location"/gt lt/constraintSimpleConstraintgt ltconstraintAnd rdfID"Constraint_CoLocated"gt          ltconstraintfirst rdfresource"LocationOfUser"/gt          ltconstraintsecond rdfresource"CoLocatedWithUser"/gt lt/constraintAndgt
ltdeonticPermission rdfID"Perm_FileAccess"gt         ltdeonticactor rdfresource"requester"/gt         ltdeonticaction rdfresource"some-ontologyAccessToSharedFiles"/gt         ltdeonticconstraint rdfresource"Constraint_CoLocated"/gt lt/deonticPermissiongt
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
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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
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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
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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