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

2. ISD 2006Ontology-based User Modeling for Web-based Information Systems 2 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

3. ISD 2006Ontology-based User Modeling for Web-based Information Systems 3 Adaptation Process Peter Brusilovsky: Methods and techniques of adaptive hypermedia. User Modeling and User-Adapted Interaction, 6(2-3):87–129, 1996.

4. ISD 2006Ontology-based User Modeling for Web-based Information Systems 4 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 users input –Personalization of systems output

5. ISD 2006Ontology-based User Modeling for Web-based Information Systems 5 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.skhttp://nazou.fiit.stuba.sk

6. ISD 2006Ontology-based User Modeling for Web-based Information Systems 6 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 personal.name John Smith false

7. ISD 2006Ontology-based User Modeling for Web-based Information Systems 7 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

8. ISD 2006Ontology-based User Modeling for Web-based Information Systems 8 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 -

9. ISD 2006Ontology-based User Modeling for Web-based Information Systems 9 Performance Relational database – –Good theoretical background –Maturity of DBMS XML – –limited by performance of used file system or XML database Ontology – –immature technologies

10. ISD 2006Ontology-based User Modeling for Web-based Information Systems 10 Reasoning Relational database, XML – –No formally defined semantics Ontology – –Relations, conditions and restrictions provide the basis for inferring additional user characteristics

11. ISD 2006Ontology-based User Modeling for Web-based Information Systems 11 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

12. ISD 2006Ontology-based User Modeling for Web-based Information Systems 12 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!

13. ISD 2006Ontology-based User Modeling for Web-based Information Systems 13 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

14. ISD 2006Ontology-based User Modeling for Web-based Information Systems 14 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

15. ISD 2006Ontology-based User Modeling for Web-based Information Systems 15 Web-based IS using User Model Standard layered architecture –Presentation layer Personalized presentation layer Click SemanticLog LogAnalyzer Factic TopK

16. ISD 2006Ontology-based User Modeling for Web-based Information Systems 16 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

17. ISD 2006Ontology-based User Modeling for Web-based Information Systems 17 Domain independent part

18. ISD 2006Ontology-based User Modeling for Web-based Information Systems 18 Domain model

19. ISD 2006Ontology-based User Modeling for Web-based Information Systems 19 Domain dependent part

20. ISD 2006Ontology-based User Modeling for Web-based Information Systems 20 Conclusions Web-based IS Adaptive Web-based IS User model is necessary for adaptation Relational representation of a model does not fulfill our needs Ontological representation of a model Semantic Web vision opens data to the world Sharing aspect is becoming more important More information about the project: –http://nazou.fiit.stuba.skhttp://nazou.fiit.stuba.sk