Tagommenders: Connecting Users to Items through Tags Written by Shilad Sen, Jesse Vig, and John Riedl (2009) Presented by Ken Hu and Hassan Hattab

Overview Introduction Tagommender o Philosophy o Dataset Tag Preference Inference o Approach o Methods Recommenders o Implicit o Explicit Results Conclusion

First, Recommenders. What is Recommender system? Two Main tasks o Recommend. o Predict.

Recommender Systems Types of recommender systems: o User-based: decides according to the user's previous choices o Item-based: decides according to related items to a selected item o SVD Problem: These methods don't consider the content of the item. Solution: Content-based Recommenders

Overview Introduction Tagommender o Philosophy o Dataset Tag Preference Inference o Approach o Methods Recommenders o Implicit o Explicit Results Conclusion

Tagging Systems Uses tags to address (categorize) items to users Tags are created by general users (More meaningful )

Tagommenders: Basically, they combine Recommenders (content- based) and tagging systems. Two main parts for Tagommenders: o They infer users’ preferences for tags based on their interactions with tags and movies o and they infer users’ preferences for movies based on their preferences for tags.

Tagommender's data set These are collected from the MovieLens website. Movie Rating Movie clicks Tag applications Tag Searches Tag Preference Ratings

Tagommender's data set

Overview Introduction Tagommender o Philosophy o Dataset Tag Preference Inference o Approach o Methods Recommenders o Implicit o Explicit Results Conclusion

Tagommender's Cycle

Inferring Tag Preference Inferring Preference using Tag Signals (Direct)

Inferring Tag Preference Inferring Preference using Item Signals (indirect)

Inferring Preference using Item Signals Sigmoid transformation is used to calculate the weight of movie m to tag t

Inferring Preference using Item Signals Methods 1.Movie-Clicks 2.Movie-log-odds-clicks 3.Movie-r-Clicks 4.Movie-r-log-odds-clicks 5.Movie-Rating 6.Movie Bayes

1- Movie-Clicks: set of movies clicked by user u

2- Movie-log-odds-clicks

3- Movie-r-Clicks 4- Movie-r-log-odds-clicks The only difference is Movie-rating is counted rather than movie clicks

5- Movie-Rating A user’s preference for a tag is the average rating for a movie under that tag. user u's rating for movie m

6- Movie-bayes A bayesian generative model for users rating for a certain tag. if the tag is relevant to a rating then the rating will be chosen from the user-tag-specific distribution Else, it will be chosen from the user background rating distribution

Which one is better?

Overview Introduction Tagommender o Philosophy o Dataset Tag Preference Inference o Approach o Methods Recommenders o Implicit o Explicit Results Conclusion

Recommenders Implicit o Tag data only o Recommend only o 2 algorithms  Implicit-tag  Implicit-tag-pop Explicit Algorithms o Use users' movie ratings o Recommend and predict o 3 algorithms  Cosine-tag  Linear-tag  Regress-tag

Implicit : Implicit-tag Vector Space Model o Inferred tag preference o Relevance weight

Implicit : Implicit-tag-pop Implicit-tag with movie popularity o Tag > clicks, clicker count > click count o Linear estimation of log function

Recommenders Implicit o Tag data only o Recommend only o 2 algorithms  Implicit-tag  Implicit-tag-pop Explicit Algorithms o Use users' movie ratings o Recommend and predict o 3 algorithms  Cosine-tag  Linear-tag  Regress-tag

Explicit : Cosine-tag Cosine similarity: rating vs tag preference

Explicit : Linear-tag Least-square fit linear regression

Explicit : Regress-tag Linear-tag with similarity between tags SVM was best to estimate h o Robustness against overfitting

Overview Introduction Tagommender o Philosophy o Dataset Tag Preference Inference o Approach o Methods Recommenders o Implicit o Explicit Results Conclusion

Results : Background Comparisons o Top-5  Compare top five recommendations o MAE  Average error of prediction Competitors o Overall-avg o User-avg o User-movie-avg o Explicit-item o Implicit-item o Funk-svd o Hybrid  Regress-tag + funk-svd

Results : Top-5

Results : MAE

Overview Introduction Tagommender o Philosophy o Dataset Tag Preference Inference o Approach o Methods Recommenders o Implicit o Explicit Results Conclusion

Introduced recommender algorithms based on user suggested tags (Tagommenders) Best at recommendation tasks Adds value at prediction tasks o Hybrid predictors does very well Other advantages o Ease to explain o Algorithmic evaluation of tag quality

Questions?