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Collaborative Filtering Shaun Kaasten CPSC 601.13 CSCW.
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Transcript of Collaborative Filtering Shaun Kaasten CPSC 601.13 CSCW.
Collaborative Filtering
Shaun Kaasten
CPSC 601.13 CSCW
Outline
What is filtering?Filtering techniquesWhy should we use CF?Examples of CF systemsVirtual communityCF design goalsEvaluation formsActive CFSummary
What is Filtering?
Information overload
Finding desired information
Eliminating undesirable
’94 Resnick et al.
Filtering Techniques (in and out)
Cognitive (content) Text in the item
Economic Costs and benefits
Mass mailings (low production costs)
Social People and judgments
Collaborative filtering – subjective evaluations of others
’87 Malone et al.
Why should we use CF?
People are better at subjective evaluationsWriting style,clarity, music, cake recipes
Benefit from seeing the history of an object’s useRead/edit wear
’95 Maltz & Ehrlich
Tapestry (1992)
Xerox PARC
Users annotate documents they read
Helped others decide what to read
FailuresNot freeNot distributedSQL interface – difficult to browse
Grouplens (1994)
Bellcore Video CF (1994)
Suggested Videos for: John A. Jamus. Your must-see list with predicted ratings:
•7.0 "Alien (1979)" •6.5 "Blade Runner" •6.2 "Close Encounters Of The Third Kind (1977)"
Your video categories with average ratings: •6.7 "Action/Adventure" •6.5 "Science Fiction/Fantasy" •6.3 "Children/Family"
The viewing patterns of 243 viewers were consulted. Patterns of 7 viewers were found to be most similar. Correlation with target viewer:
•0.59 viewer-130 ([email protected]) •0.55 bullert,jane r ([email protected])
Bellcore Community Web Browser (1995)
Movielens (1998?)
Web CF: Amazon Customer Reviews
Web CF: Cnet User Opinions
Web CF: MSDN Article Ratings
Virtual Community
’95 Hill et al.
Influence each other without interacting
Share benefits of collaboration without costsTime – developing personal relationshipsPrivacySynchronous communication
No intelligent agents (other than people)
CF Design Goals: Bellcore & Grouplens
Common Easy participation People power, not agents Prediction accuracy increases with user base size
Grouplens Compatibility Privacy Rich recommendations
Bellcore Works for groups, not just individuals Recommendations should include confidence
Evaluation Forms
ExplicitMusic reviews on AmazonGrouplens- grading of Usenet message
ImplicitGrouplens – monitor how long a user reads
an article
History-Enriched Digital Objects
’94 Hill et al.
Trade off: Effort vs. Rewards
’95 Hill et al.
Finding Similar Tastes
Compute correlation coefficients for the user’s reviews and others
Use as weights to combine the ratings for current article
Correlation avoids differences of scale interpretation
’94 Resnick et al.
Cold Start Problem
Profile needed to find similar tastesTraining periodNo immediate benefit for user (Grudin’s
rule)
Restricted from new areas
’95 Maltz & Ehrlich
Active CFPassive No direct connection between evaluator & reader Works for: many documents in a single database
Active Intent to share knowledge with particular people Works for: distributed systems, where just finding
sources is difficult Benefit increases with the divergence of the
documents
’95 Maltz & Ehrlich
Case Study: Computer Support Center
Expectation: workers use on-line or printed documentation to answer problems
Finding: rely on each other
Information mediator Skilled at finding and applying info
’95 Maltz & Ehrlich
Build a system to support…
Collaboration and information sharing amongst colleagues
Information mediators sending out references and commentary of useful documents
’95 Maltz & Ehrlich
What informal methods are missing
Contextual information Name, source, date, sender information
Ease of use Add annotations Return benefits early - no cold start
Flexibility Method of distribution, comments and context No set roles
’95 Maltz & Ehrlich
The Pointer System
Distribution of Pointers
Private database – bookmarks
Email Individuals Subscribe-only mailing lists
Information digests Pre-designed document – newsletters, reports,
etc.
’95 Maltz & Ehrlich
Challenging Common Theories
Comment providers should be anonymous
Knowing something about commenter is critical to evaluating the usefulness of that document
’95 Maltz & Ehrlich
Challenging Common Theories
Information finders should be freed from addressing and sending mail
Users really do have recipients in mind when they discover information
Irony of Active CF
Recipients are passiveCannot use system to find reviewed
information
’95 Maltz & Ehrlich
Summary
Choice under uncertaintyBenefit from knowledgeable people
Virtual community of experts (?)
Active CF systems help point colleagues to informationPassive CF help ‘explorers’ learn from the community