ontology-based user modeling for web-based information systems anton andrejko, michal barla and...
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Ontology-based User Modeling for Web-based Information
Systems
Anton Andrejko, Michal Barla and Mária Bieliková
{andrejko, barla, bielik}@fiit.stuba.sk
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Web-based IS and User Modeling
• Motivation:
– Users with different knowledge and needs
– Exponential growth of information on the Web
People are overloaded with information
Finding relevant information can be nearly impossible
• Solution:
• Focus on individual user and her needs
Personalization of content-oriented web-based IS
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Data about user
User ModelInformation
System
User Modeling
Adaptation
Adaptation effect
Collects
Processes
Processes
Adaptation Process
Peter Brusilovsky: Methods and techniques of adaptive hypermedia. User Modeling and User-Adapted Interaction, 6(2-3):87–129, 1996.
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User Model
• Beliefs about the user that include preferences, knowledge and attributes (characteristics) for a particular domain
• Used to adapt the content, presentation or navigation
– Filtering on behalf of the user
– Interpretation of the user’s input
– Personalization of system’s output
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Presentation Overview
• Overview of various representation of user model
• Example of incorporation of a model into IS architecture
• Example of an ontology-based user model
– Used at the project Tools for Acquiring, Organizing and Presenting Information and Knowledge in an Environment of Heterogeneous Information Sources
– http://nazou.fiit.stuba.sk
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User Model Representations
• Relational database– User Model represented as a set of interconnected tables
– Characteristic = attribute in the relational data model
• XML-based language– Characteristics represented as values or attributes of
specific tags
<record>
<key>personal.name</key>
<value>John Smith</value>
<firsttimeupdated>false</firsttimeupdated>
</record>
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User Model Representations
• Ontology-based representation
– Ontology ~ an explicit specification of the conceptualization of a domain
– Using RDF/OWL formalisms
• Define classes and properties
• Define a vocabulary for describing classes and properties
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Flexibility, changeability
• Uniform representation for different kinds of characteristics
• Relational database - – User model created as an overlay of a domain model
– User model contains semi-structured data
– Changing the structure of tables brings often problems
• XML -
• Ontology -
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Performance
• Relational database –
– Good theoretical background
– Maturity of DBMS
• XML –
– limited by performance of used file system or XML database
• Ontology –
– immature technologies
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Reasoning
• Relational database, XML –
– No formally defined semantics
• Ontology –
– Relations, conditions and restrictions provide the basis for inferring additional user characteristics
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Easy of use
• Relational database - – Most of content-oriented IS already use some rel. DB
– Mature technology
• XML - – Many tools available
– Mature technology
• Ontology - – Lack of experts, tools
– Immature technology
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Understandability
• Can domain expert work easily with a model?
• Relational database -
– Relational calculus can be hard to understand (M:N)
• XML -
• Ontology -
– Thinking in terms of classes, instances, relations and restrictions is close to thinking of an expert
• We need a visualization for complicated models!
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Shareability and reusability
• Shareability – needed for the Semantic Web vision
• Relational database - – Proprietary, platform-dependent
• XML – – Platform independent
– Everyone can invent his own names for tags
• Ontology – – Easy combining of existing models into the new ones
Creation of an “overlay model” is intuitive
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User model in web-based IS
• Web-based IS for people looking for a job
• Offers are retrieved from the Web and processed into ontological representation (domain model)
• User is adaptively navigated to offers of her interest
• Various presentation tools integrated in portal solution
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Web-based IS using User Model
• Standard layered architecture
– Presentation layer Personalized presentation layer
Portal
HTMLfragments
Events
Presentation
Adaptation
Presentation tools
Presentation
Adaptation
Input / Feedback
Webbrowser
Server-sidelogging
Client-sidelogging
User characteristic
evaluation
EventsEvents
Presentationlayer
Personalizationlayer
User modelinglayer
Server ClientPersonalized presentation layer
Events
Domain model
User model
Click
SemanticLogLogAnalyzer
FacticTopK
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User Model
• User model consists of two parts
– Domain-dependent
• Use the same vocabulary as a domain model
– Domain-independent
• Describe user as a person
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UserCharacteristic
hasRelevance Instance c:LevelOrdering
hasConfidence Instance c:LevelOrdering
contributesTo Instance* Goal
GenericUserCharacteristic
relatesTo Instance
is a
DomainSpecificUser
User
hasBirthday String
hasCharacteristic Instance* GenericUserCharacteristic
includes Instance* DomainSpecificUser
hasName String
hasCharacteristic* includes*
Domain independent part
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Domain model
jo:JobOffer
jo:hasPrerequisite*
jo:offersPosition
jo:Organization
jo:isOfferedByjo:isOfferedVia
jo:hasBenefit*
jo:hasApplyInformation*
r:Region
jo:hasDutyLocation*
jo:Salary
jo:hasSalary
jo:offers*jo:mediates*
jo:isBasedAt
r:isPartOf* r:consistsOf*
jo:ApplyInformation
c:ProfessionClassification
jo:Prerequisite
jo:Benefit
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Domain dependent part
gu:DomainSpecificUser
JobOfferSpecificUser
hasVisitedOffer Instance* VisitedOffer
hasCharacteristic Instance* JobOfferSpecificUserCharacteristic
isa
JobOfferSpecificUserCharacteristic
relatesTo Instance
jo:ApplyInformation
jo:Benefit
jo:ContactInformation
jo:ContractType
jo:JobTerm
jo:Responsibility
jo:Salary
jo:TravelingLevel
jo:ManagementLevel
jo:Prerequisite
gu:UserCharacteristic
is a
VisitedOffer
hasRating Integer*
hasJobOffer Instance* jo:JobOffer
hasDateOfVisit String*
hasCharacteristic*hasVisitedOffer*
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Conclusions
• Web-based IS Adaptive Web-based IS
• User model is necessary for adaptation
• Relational representation of a model does not fulfill our needsOntological representation of a model
• Semantic Web vision “opens” data to the worldSharing aspect is becoming more important
• More information about the project:
– http://nazou.fiit.stuba.sk