creators_name: Stern, David creators_name: Herbrich, Ralf creators_name: Graepel, Thore type: conference_item datestamp: 2009-04-06 19:08:47 lastmod: 2009-04-07 14:02:12 metadata_visibility: show title: Matchbox: Large Scale Online Bayesian Recommendations ispublished: pub full_text_status: public pres_type: paper abstract: We present a probabilistic model for generating personalised recommendations of items to users of a web service. The Matchbox system makes use of content information in the form of user and item meta data in combination with col- laborative filtering information from previous user behavior in order to predict the value of an item for a user. Users and items are represented by feature vectors which are mapped into a low-dimensional ‘trait space’ in which similarity is measured in terms of inner products. The model can be trained from different types of feedback in order to learn user-item preferences. Here we present three alternatives: direct observation of an absolute rating each user gives to some items, observation of a binary preference (like/ don’t like) and observation of a set of ordinal ratings on a user- specific scale. Efficient inference is achieved by approxi- mate message passing involving a combination of Expecta- tion Propagation (EP) and Variational Message Passing. We also include a dynamics model which allows an item’s popu- larity, a user’s taste or a user’s personal rating scale to drift over time. By using Assumed-Density Filtering (ADF) for training, the model requires only a single pass through the training data. This is an on-line learning algorithm capable of incrementally taking account of new data so the system can immediately reflect the latest user preferences. We eval- uate the performance of the algorithm on the MovieLens and Netflix data sets consisting of approximately 1,000,000 and 100,000,000 ratings respectively. This demonstrates that training the model using the on-line ADF approach yields state-of-the-art performance with the option of improving performance further if computational resources are available by performing multiple EP passes over the training data. date: 2009-04 pagerange: 111-111 event_title: 18th International World Wide Web Conference event_location: Madrid, Spain event_dates: April 20th-24th, 2009 event_type: conference refereed: TRUE citation: Stern, David and Herbrich, Ralf and Graepel, Thore (2009) Matchbox: Large Scale Online Bayesian Recommendations. In: 18th International World Wide Web Conference, April 20th-24th, 2009, Madrid, Spain. document_url: http://www2009.eprints.org/12/1/p111.pdf