Session: Social Recommendation
Date: Monday, September 10, 16:30-18:00
- Inspectability and Control in Social Recommenders
by Bart Knijnenburg, Svetlin Bostandjiev, John O’Donovan and Alfred Kobsa
Users of social recommender systems may want to inspect and control how their social relationships influence the recommendations they receive, especially since recommendations of social recommenders are based on friends rather than anonymous “nearest neighbors”. We performed an online user experiment (N=267) with a Facebook music recommender system that gives users control over the recommendations, and explains how they came about. The results show that inspectability and control indeed increase users’ perceived understanding of and control over the system, their rating of the recommendation quality, and their satisfaction with the system.
- Spotting Trends: The wisdom of the few
by Xiaolan Sha, Daniele Quercia, Matteo Dell’Amico and Pietro Michiardi
Social media sites have used recommender systems to suggest items users might like but are not already familiar with. These items are typically movies, books, pictures, or songs. Here we consider an alternative class of items – pictures posted by design-conscious individuals. We do so in the context of a mobile application in which users find “cool” items in the real world, take pictures of them, and share those pictures online. In this context, temporal dynamics matter, and users would greatly profit from ways of identifying the latest design trends. We propose a new way of recommending trending pictures to users, which unfolds in three steps. First, two types of users are identified – those who are good at uploading trends (trend makers) and those who are experienced in discovering trends (trend spotters). Second, based on what those “special few” have uploaded and rated, trends are identified early on. Third, trends are recommended using existing algorithms. Upon the complete longitudinal dataset of the mobile application, we compare our approach’s performance to a traditional recommender system’s.
- Real-Time Top-N Recommendation on Social Streams
by Ernesto Diaz-Aviles, Lucas Drumond, Lars Schmidt-Thieme and Wolfgang Nejdl
The Social Web is successfully established, and steadily growing in terms of users, content and services. People generate and consume data in real-time within social networking services, such as Twitter, and increasingly rely upon continuous streams of messages for real-time access to fresh knowledge about current affairs. In this paper, we focus on analyzing social streams in real-time for personalized topic recommendation and discovery. We consider collaborative filtering as an online ranking problem and present Stream Ranking Matrix Factorization – RMFX -, which uses a pairwise approach to matrix factorization in order to optimize the personalized ranking of topics. Our novel approach follows a selective sampling strategy to perform online model updates based on active learning principles, that closely simulates the task of identifying relevant items from a pool of mostly uninteresting ones. RMFX is particularly suitable for large scale applications and experiments on the “476 million Twitter tweets” dataset show that our online approach largely outperforms recommendations based on Twitter’s global trend, and it is also able to deliver highly competitive Top-N recommendations faster while using less space than Weighted Regularized Matrix Factorization (WRMF), a state-of-the-art matrix factorization technique for Collaborative Filtering, demonstrating the efficacy of our approach.
- On Top-k Recommendation using Social Networks
by Xiwang Yang, Harald Steck, Yang Guo and Yong Liu
Recommendation accuracy can be improved by incorporating trust relationships derived from social networks. Most recent work on social network based recommendation is focused on minimizing the root mean square error (RMSE). Social network based top-k recommendation, which recommends to a user a small number of items at a time, is not well studied. In this paper, we conduct a comprehensive study on improving the accuracy of top-k recommendation using social networks. We first show that the existing social-trust enhanced Matrix Factorization (MF) models can be tailored for top-k recommendation by including observed and missing ratings in their training objective functions. We also propose a Nearest Neighbor (NN) based top-k recommendation method that combines users’ neighborhoods in the trust network with their neighborhoods in the latent feature space. Experimental results on two publicly available datasets show that social networks can significantly improve the top-k hit ratio, especially for cold start users. Surprisingly, we also found that the technical approach for combining feedback data (e.g. ratings) with social network information that works best for minimizing RMSE works poorly for maximizing the hit ratio, and vice versa.