CoOL: A Context Ontology CoOL: A Context Ontology Language to Enable Contextual Language to Enable Contextual InteroperabilityInteroperability
Thomas Strang, Claudia Linnhoff-Popien, and Korbinian Frank
German Aerospace Centor (DLR). Oberpfaffenhofen, Germany
Ludwig-Maximilians-University (LMU), Munich, Germany
Presented by Sangkeun Lee IDS Lab.
Copyright 2008 by CEBT
IntroductionIntroduction
The pervasive computing trend is driving a need for context-aware service architectures involved in a service interaction
To reduce the amount of required user actions
Various actors
– E.g. any user, any service provider, environment, or third parties
A key to context information in context-aware system is a
Well designed model to describe contextual facts and contextual interrelationships
Previous works lack formality
The context modeling approach in this paper tries to close the formality gap by using Ontologies
Another example: CONON (Context Ontology)
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What is Context?What is Context?
Definition of Context Information
“A context information is any information which can be used to characterize the state of an entity concerning a specific aspect”
“An entity is a person a place or in general an object”
“An aspect is a classification, symbol or value-range, whose subsets are a superset of all reachable states”
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Reference: “Trends in Mobile Computing From Mobile Phone to Context-Aware Service Platform” by Thomas Strang
Copyright 2008 by CEBT
What is Context? (cont’d)What is Context? (cont’d)
Definition of Context
“A context is the set of all context information characterizing the entities relevant for a specific task in their relevant aspects”
“An entity is relevant for a specific task, if its state is characterized at least concerning one relevant aspect”
“An aspect is relevant, if the state with respect to this aspect is accessed during a specific task or the state has any kind of influence on the task”
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Reference: “Trends in Mobile Computing From Mobile Phone to Context-Aware Service Platform” by Thomas Strang
Copyright 2008 by CEBT
Context-awarenessContext-awareness
Definition of Context Awareness:
“A system is context aware if it uses any kind of context information before or during service provisioning or service usage”
Two main benefits from Context Awareness:
Adaptation of services to changes in environment
reduces amount of interaction with user
– Improvement of UI (particularly on small mobile devices)
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Reference: “Trends in Mobile Computing From Mobile Phone to Context-Aware Service Platform” by Thomas Strang
Copyright 2008 by CEBT
Ontologies and the Context Ontology Ontologies and the Context Ontology LanguageLanguage
Challenge to describe contextual facts and interrelationships in a precise and traceable manner
“print document on printer near to me”
It is required to have a precise definition of terms used in the task, particularly what “near” means to “me”
It is highly desirable that each participating party in a service interaction share the same interpretation of the meaning “behind” it
– Shared understanding
Ontologies
May be stored at different places and created by different authors, which offers flexibility and extensibility
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Context Ontology Language (CoOL)Context Ontology Language (CoOL)
CoOL Core
OWL and DAML+OIL
F-Logic
CoOL Integration
A collection of schema and protocol extensions as well as common subcontepts, enabling the use of CoOL Core in several service frameworks (e.g Web Service)
Out of focus of this paper
Having a projection of the model in multiple ontology languages enables that
Developer may use any of languages which seems to be adequate
– Using OWL because of wide range of available tools
– Using F-logic because of its rule based extensibility
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ASC ModelASC Model
Aspect-Scale-Context (ASC) model
Named after the core concepts
Each aspect aggregate one or more scales
Each scale aggregates one or more context information
hasAspect, hasScale, constructedBy
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ASC Model ExamplesASC Model Examples
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Reference: “Ubiquitous Computing :Context and Context-Awareness”, University of Innsbruck, Lecture slide from SS 2005
Another Example:SpartialDistanceAspect - MeterScale,KilometerScale – 10, 20
Fahrenheit's temperature scale Celsius temperature scale
Specific Values
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OperationsOperations
IntraOperation
Mapping function from one scale to at least one other of the already existing scales of the same aspect
InterOperation
Scales which require access to scales of one or more other aspects can be defined using InterOperations
E.g.
– “KilometerPerHourScale” of a “SpeedAspect” can be defined by using an InterOperation with two Parameter, delta_s and delta_t where
delta_s is from an aspect “SpatialDistanceAspect”
delta_t is from an aspect “DurationAspect”
MetricOperation
Compare two context information instances
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Transfer ModelTransfer Model
ASC model may be used as transfer model to employ the knowledge expressed in other context models
Example: Henricksen
Context extension to the Object-Role Modeling approach
The basic modeling concept in ORM is fact
Henricksen extended ORM to allow fact types to be categorized either as static or dynamic (profiled, sensed, derived)
Using ASC Model
Facts can be modeled as “context information”
Classification can be mapped by introducing a “quality aspect” consisting the element {static, dynamic profiled, dynamic sensed, dynamic derived}
dependOn relation can be expressed using Intra/InterOperations
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Relation to DAML-SRelation to DAML-S
DAML-S : ontology of services
ServiceProfile, ServiceModel, and ServiceGrounding
Extension: ServiceContext
– May serve as a formal description of a service’s contextual interoperability by providing a comprehensive but extensible model based on the ASC model
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Motivation: Motivation: MNM Service Model and the Context ExtensionMNM Service Model and the Context Extension
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System ArchitectureSystem Architecture
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The authors focus on the context provider domain as introduced in the previous page
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Discussion & ConclusionsDiscussion & Conclusions
Discussion
ASC model
– The authors gives us a different point of view (compare to CONON)
– What’s weak points and strong points?
It is interesting the authors classified actors into
– Context Providers, Service Providers, Customers
– Who can be Context Providers?
Conclusions
The authors introduced ASC model as a base model to express how some context information can be used to characterize the state of an entity concerning a specific aspect
ASC model fits into a general purpose service model
– Context Extension : Making any service interaction based on that model context-aware
ASC model as transfer model
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