Ontology-based User Modeling for Web-based Information Systems Anton Andrejko, Michal Barla and Mária Bieliková {andrejko, barla, bielik}@fiit.stuba.sk

Ontology-based User Modeling for Web-based Information

Systems

Anton Andrejko, Michal Barla and Mária Bieliková

{andrejko, barla, bielik}@fiit.stuba.sk

ISD 2006 Ontology-based User Modeling for Web-based Information Systems

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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

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



Documents

Ontology-based User Modeling for Web-based Information Systems Anton Andrejko, Michal Barla and Mária Bieliková {andrejko, barla, bielik}@fiit.stuba.sk