Collaborative Filtering and
Recommender Systems
Brian Lewis
INF 385Q
Knowledge Management Systems
November 10, 2005
Presentation Outline
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Collaborative filtering and recommender systems defined
Novel example
Readings - overview & key concepts
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Glance, Arregui & Dardenne (1997)
Konstan, Miller, et al. (1997)
Proctor & McKinlay (1997)
Conclusions
References
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Collaborative Filtering defined
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"Based on the premise that people looking for
information should be able to make use of what
others have already found and evaluated." (Maltz
& Ehrlich, 1995)
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"Technique for dealing with overload in
information environments" (Procter & McKinlay,
1997)
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Recommender systems defined
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Systems that evaluate quality based on the
preferences of others with a similar point of view
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Hobo symbols from http://www.slackaction.com/signroll.htm
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Hobo symbols as RS?
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Specific to a community
Implicit and explicit signs
Filtered through encoding
Cold-start problem?
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Compare to today
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Recommend
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Don't recommend
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Glance, Arregui & Dardenne (1997)
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Knowledge Pump
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Designed for use with an electronic repository
Document management and recommendation
Community-centered collaborative filtering
Characteristics
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Social filtering
Content-based filtering
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Glance, Arregui & Dardenne (1997)
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User-item matrix of ratings
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Konstan, Miller, et al. (1997)
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GroupLens
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Pilot study - Usenet news
Rating system
Integrate into an existing system/existing users
Use existing applications - open architecture
Characteristics
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High volume / high turnover
High noise information resource
Sparse set of ratings
Predictive utility cost/benefit
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Konstan, Miller, et al. (1997)
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Predictive utility
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Risk - costs of misses and
false positives
Benefit - values of hits and
correct rejections
Usenet has high predictive utility
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High volume
Value of correct rejection is high
Risk of a miss is low
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Konstan, Miller, et al. (1997)
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Challenges
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Ratings sparsity
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"first-rater" problem
Partition articles into clusters
Capture implicit ratings
Filter bots
Performance challenges
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System architecture
Composite users
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Proctor & McKinlay (1997)
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Social Affordances and Implicit Ratings
How implicit approaches might be improved
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Sources of rating and recommendation data
Context of ratings and recommendations
Real and virtual groups
Privacy and accessibility
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Proctor & McKinlay (1997)
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Characteristics
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Explicit ratings systems
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Reader ratings based approach is expensive
How do you deal with trust issues?
Implicit ratings systems
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Free to users
How do you capture context?
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Proctor & McKinlay (1997)
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Social Affordances
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"…making the potential for social (inter)action visible."
How can activities be made visible? (explicitly)
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Web bookmarks
Sharable annotations
How can activities be made visible? (implicitly)
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Copy browsing behavior of experts (virtual groups)
Documents context in a group of documents (discourse
analysis)
Temporal coherence
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Proctor & McKinlay (1997)
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Extracting implicit ratings from web behavior
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Virtual group proxies
Proxy cache analysis
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Nominal rating
Frequency
Sequential accountability
Distributional accountability
Sources
Topical coherence
Temporal coherence
Privacy Issues
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Conclusions
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Many different issues
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Context dependent
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Diverse domains / communities
Diverse content needs
Nature of information
Predictive utility
Very creative solutions to draw from
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References
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Glance, N., Arregui, D., & Dardenne, M. (1997). Knowledge Pump:
Community-centered collaborative filtering. 5th DELOS workshop on
filtering and collaborative filtering, Budapest, Hungary.
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Konstan, J., Miller, B., Maltz, D., Herlocker, J., Gordon, L. and Riedl, J.
(1997), Applying collaborative filtering to usenet news, Communication
of the ACM, 40(3), 77-87.
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Maltz, D. and Ehrlick, K. (1995). Pointing the way: active collaborative
filtering. CHI '95, ACM Press.
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Procter, R. and A. McKinley (1997). Social affordances and implicit
ratings for social filtering on the Web. DELOS workshop on
collaborative filtering, Budapest, Hungary.
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Questions
Questions live here
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