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Semantic Web Workshop 26.4.2002

Exploiting Synergy Between Ontologies and Recommender Systems. Stuart E. Middleton, Harith Alani Nigel R. Shadbolt, David C. De Roure Intelligence, Agents and Multimedia Research Group Dept of Electronics and Computer Science University of Southampton United Kingdom

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Semantic Web Workshop 26.4.2002

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  1. Exploiting Synergy Between Ontologies and Recommender Systems Stuart E. Middleton, Harith Alani Nigel R. Shadbolt, David C. De Roure Intelligence, Agents and Multimedia Research Group Dept of Electronics and Computer Science University of Southampton United Kingdom Email: sem99r@ecs.soton.ac.uk Web: http://www.iam.ecs.soton.ac.uk Semantic Web Workshop 26.4.2002

  2. Exploiting Synergy Between Ontologies and Recommender Systems • Cold-start and interest acquisition problems • Quickstep architecture and approach • OntoCoPI approach • Integration of Quickstep, Ontology and OntoCoPI • Empirical evaluation • Issues arising from empirical evaluation • Future work Semantic Web Workshop 26.4.2002

  3. Exploiting Synergy Between Ontologies and Recommender Systems • Cold start and interest acquisition problems • Recommender systems reduce WWW information overload • Observe behaviour to profile user interests • Suffer from cold-start problems • New-system and new-user cold start • Ontologies hold knowledge about a domain • Domain knowledge held is commonly static in nature • Acquiring ever changing interests is challenging • Synergy between ontologies and recommender systems • Ontologies can bootstrap recommender systems • Recommender systems can acquire interests for an ontology Semantic Web Workshop 26.4.2002

  4. Exploiting Synergy Between Ontologies and Recommender Systems World Wide Web Users Profiles Classifier Recommender Classified papers • Quickstep architecture and approach • Research papers • TF vector representation • Research topic ontology • Classifier • k-nearest neighbour • Users can add examples • Classified paper database • Grows as users browse • Profiler • Feedback and browsed papers give time/interest profile • Time decay function computes current interests • Recommender • Recommends new papers on topics of interest Semantic Web Workshop 26.4.2002

  5. Exploiting Synergy Between Ontologies and Recommender Systems Project B 2001 1999 Project A • OntoCoPI approach • Identifies communities of practice using an ontology • Informal groups of individuals sharing an interest • Network analysis applied to a populated ontology • Breadth-first search over selected relationships • Discovers connections that infer common interest Semantic Web Workshop 26.4.2002

  6. Exploiting Synergy Between Ontologies and Recommender Systems • OntoCoPI approach • Identifies communities of practice using an ontology • Informal groups of individuals sharing an interest • Network analysis applied to a populated ontology • Breadth-first search over selected relationships • Discovers connections that infer common interest Project B 2001 1999 Project A Semantic Web Workshop 26.4.2002

  7. Exploiting Synergy Between Ontologies and Recommender Systems • OntoCoPI approach • Identifies communities of practice using an ontology • Informal groups of individuals sharing an interest • Network analysis applied to a populated ontology • Breadth-first search over selected relationships • Discovers connections that infer common interest Project B 2001 1999 Project A Semantic Web Workshop 26.4.2002

  8. Exploiting Synergy Between Ontologies and Recommender Systems Ontology OntoCoPI Quickstep • Integration of Quickstep, Ontology and OntoCoPI • New-system cold start • Ontology bootstraps • new-system profiles Semantic Web Workshop 26.4.2002

  9. Exploiting Synergy Between Ontologies and Recommender Systems • Integration of Quickstep, Ontology and OntoCoPI • New-system cold start • Ontology provides each user’s publications • Quickstep computes publication topic classifications • Bootstrap profile is computed from publication topics 2001 2001 2002 1999 Publications for each user Ontology Quickstep Semantic Web Workshop 26.4.2002

  10. Exploiting Synergy Between Ontologies and Recommender Systems Ontology OntoCoPI Quickstep • Integration of Quickstep, Ontology and OntoCoPI • New-system cold start • Ontology bootstraps • new-system profiles • New-user cold start • OntoCoPI and Ontology • bootstraps new-user profiles Semantic Web Workshop 26.4.2002

  11. Exploiting Synergy Between Ontologies and Recommender Systems • Integration of Quickstep, Ontology and OntoCoPI • New-user cold start • Ontology provides new user’s publications • OntoCoPI provides a set of similar user’s to the new user • Bootstrap using similar profiles and previous publications 2002 Ontology 2001 2001 Publications for new user 1999 Relationships to new user OntoCoPI Similar users Quickstep Semantic Web Workshop 26.4.2002

  12. Exploiting Synergy Between Ontologies and Recommender Systems Ontology OntoCoPI Quickstep • Integration of Quickstep, Ontology and OntoCoPI • New-system cold start • Ontology bootstraps • new-system profiles • New-user cold start • OntoCoPI and Ontology • bootstraps new-user profiles • Interest acquisition • Recommender updates ontology • interests every day Example profile 1st April 2002, Recommender Systems, 6.0 1st April 2002, Interface Agents, 2.9 1st April 2002, Agents, 0.9 2nd April 2002, Recommender Systems, 5.0 2nd April 2002, Interface Agents, 2.6 2nd April 2002, Agents, 0.8 … Semantic Web Workshop 26.4.2002

  13. Exploiting Synergy Between Ontologies and Recommender Systems Precision Error rate New-system bootstrapping 0.35 0.06 New-user bootstrapping 0.84 0.55 • Empirical evaluation Measured the reduction in the recommender cold-start • Used logged browsing behaviour from a real trial • Quickstep trial logs, 9 users, first 7 weeks of browsing used • Measured convergence to a post cold-start state • Week 7 used for post cold-start state • New-system bootstrap performance measured • New-user bootstrap performance measured Semantic Web Workshop 26.4.2002

  14. Exploiting Synergy Between Ontologies and Recommender Systems • Issues arising from empirical evaluation • Is the cold-start overcome? • New-system bootstrapping works well • Old interests were correctly identified • Recent interests harder to get from publications • New-user bootstrapping too error prone • Communities of practice were not focused enough • Not selective enough when taking similar users interests • Is the interest-acquisition problem overcome? • Up-to-date interest profiles are acquired daily • Once the cold-start is over, profiles closely match behaviour Semantic Web Workshop 26.4.2002

  15. Exploiting Synergy Between Ontologies and Recommender Systems • Issues arising from empirical evaluation • How does the quality of the ontology effect the quality of the communities of practice identified? • Ontology was only partially populated • We only used users who had previous publications • OntoCoPI relationship weights not custom to our problem • Can the new-user algorithm be significantly improved? • Could pick topics only a majority of similar users like • OntoCoPI confidence values can weight user similarity • What other information sources could be used? • Other university databases • Structured web pages with associated metadata Semantic Web Workshop 26.4.2002

  16. Exploiting Synergy Between Ontologies and Recommender Systems • Issues arising from empirical evaluation • Will our approach work with other problem domains? • Classifier needs textual information sources • User behaviour must be monitored • Need an ontology for the domain • Classifier needs a new training set of class examples Semantic Web Workshop 26.4.2002

  17. Exploiting Synergy Between Ontologies and Recommender Systems • Future work • Further recommender / ontology experimentation • Improve the set of relationships and weights used • Find a better new-user algorithm • Conduct further trials with some more users • Look into profiling context and task structure • Foxtrot recommender system • Year long trial, over 100 staff and students • Searchable paper database with recommendation facility • Users can visualize and update their own profiles • OntoCoPI • Prototype enhanced and developed further • Evaluation planned with people in the IAM lab Semantic Web Workshop 26.4.2002

  18. Exploiting Synergy Between Ontologies and Recommender Systems • Quickstep architecture and approach • K-Nearest Neighbour - kNN • TF vector representation • Examples exist in a term-vector space • New papers are added to this space • Classification is a function of its ‘closeness’ to examples Example paper (class1) Example paper (class2) Unclassified paper Term-vector space Semantic Web Workshop 26.4.2002

  19. Exploiting Synergy Between Ontologies and Recommender Systems • Quickstep architecture and approach • Profiling • Time/Interest profile • Is-a hierarchy infers topic interest in super-classes • Time decay function biases towards recent interests Super-class (agents) Interest Subclass (multi-agent systems) Subclass (recommender systems) Time Current interests Semantic Web Workshop 26.4.2002

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