Recommendations Meet Web Browsing: Enhancing Collaborative Filtering Using Internet Browsing Logs
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Recommendations Meet Web Browsing: Enhancing Collaborative Filtering using Internet Browsing Logs Royi Ronen Elad Yom-Tov Gal Lavee Microsoft Israel Microsoft Research Israel Microsoft Israel [email protected] [email protected] [email protected] Abstract—Collaborative filtering (CF) recommendation sys- tailed: most people buy few products, and only a few buy tems are one of the most popular and successful methods for many of them. Similarly, when new items (so-called ”cold recommending products to people. CF systems work by finding items”) are introduced into the item catalog, it is hard for CF similarities between different people according to their past recommendation systems to recommend these items. Another purchases, and using these similarities to suggest possible items of shortcoming of CF recommendation systems is that they have interest. In this work we show that CF systems can be enhanced limited capacity to consider temporal changes in user interests, using Internet browsing data and search engine query logs, both of which represent a rich profile of individuals’ interests. particularly short-term purchase intent. We introduce two approaches to enhancing user modeling Internet activity logs are the time-stamped list of sites using these data. We do not assume the existence of explicit visited by users as they browse the Internet. Internet activity ratings, but rather rely on unweighted, positive signals, that are logs are usually collected from users who have agreed to available in most commercial contexts. We demonstrate the value sharing these data through toolbars and similar browser add- of our approach on two real datasets each comprising of the ins. Search engine logs are the recordings of all queries sub- activities of tens of thousands of individuals. The first dataset mitted to an Internet search engine. Internet activity logs and details the downloads of Windows Phone 8 mobile applications queries to search engines have long been known to represent and the second - item views in an online retail store. Both datasets the physical and virtual behaviors of people [2]. As such, are enhanced using anonymized Internet browsing logs. they have been used to track disease distributions [3], identify Our results show that prediction accuracy is improved by users with specific ailments [4] and pinpoint physical events up to 72%. This improvement is largest when building a model [5]. These data are highly indicative of personal preferences which can predict for the entire catalog of items, not just popular and behaviors thus making it possible to predict demographics ones. Finally, we discuss additional benefits of our approach, (age, gender, income, etc.) of users through their analysis [6]. which include: improved recommendations for users with few past purchases and enabling recommendations based on short- Hence, in this paper we aim to overcome the shortcomings term purchase intent. of basing CF recommendation systems solely on the consump- tion of catalog items by enhancing these systems with Internet activity logs and Internet search engine logs. Our hypothesis I. INTRODUCTION is that the rich data representation enabled by this data can Recommendation (or recommender) systems are informa- be leveraged to enhance CF based recommendation systems. tion filtering systems designed to suggest products or services Furthermore, this representation goes towards addressing the which would be of interest to people. One of the most popular cold user problem, as even users who never consumed an approaches to making recommendation is that of Collaborative item from the catalog, have their preferences encoded by the Filtering (CF) [1]. CF-based recommendation systems work by sites they visited, allowing the system to find other users with defining a similarity between people according to their product similar item preferences. preference. Each user is then presented with recommended items consumed by other users similar to themselves. A. Background and Related Work CF systems utilize information of the products consumed Recommendation systems technologies aim to serve rel- by users to make their recommendations. This can be con- evant items from the catalog to a user based on the user’s sidered a strength of the approach, as the most pertinent previous interaction with the catalog (e.g. rating or purchasing information for making recommendations is the consumption catalog items). There exist several families of approaches to of the items from the catalog. However, this can also be the solution of these problems. The chronologically earliest of considered a weakness, as a definition of similarity between these is the content-based recommendation paradigm [7]. In users based solely on their consumption of a particular class this approach, features of catalog items, which are in general of items is very limited. Furthermore, this approach makes it unstructured real world entities such as movies or games, are difficult to provide good item recommendations to users who defined and encoded into a machine analyzable form. Using are new to the system and have made few, if any, purchases this representation, along with user’s past interactions with the (the so-called ”cold users”). The problem of making recom- item catalog, a model of the user preferences is constructed mendations to new users is especially troublesome in many which is capable of scoring all items in the catalog the user has real-world recommendation systems, where the distribution not yet interacted with. Often TF-IDF vectors derived textual of the number of items consumed by each user is heavy descriptions are used to create such a representation. A alternate approach to the construction of recommenda- entities that already have a recommendation system (especially tion systems is the CF paradigm [8]. The underlying intuition is one based on MF) in place. to use the item catalog interactions of other users with “similar preferences” to select appropriate items to recommend. A key B. Contributions idea is that similarity between users can be inferred solely by their interaction behavior. Thus, the classical formulation of CF The main contributions of this work are: algorithms ignores all attributes of user information and make use only of the user/item matrix of interactions (e.g. ratings • Novel, domain-independent and privacy preserving or purchases). This gives CF techniques better generalization methods for enhancing MF models by expanding the across application domains, as, unlike content-based methods, user-item matrix and by imputation of the user-item there is no longer any need for defining and collecting meta- matrix, using browsing logs and search query logs. data features to encode items and/or users. • Extensive experimentation with two real datasets from Within the CF paradigm there are two main classes of different domains, constituting different interaction algorithms. In the first of these classes, neighborhood methods signal types: (1) smartphone app purchases; and (2) [9], [10], use the implicit similarity of users/items to select online retail store item clicks. We present both quan- catalog items to recommend to the user. Item based neighbor- titative empirical results and a qualitative anecdotal hood methods [10] recommend items similar to other items evaluation to support the merits of our proposed the user has consumed. A user-based neighborhood method approach. [9] recommends items rated highly by users similar to the • Reports on negative results for the benefit of the user requesting the recommendation. community. More recently, a class of approaches called Matrix Fac- torization (MF) (also known as latent factor modeling), has II. MATRIX FACTORIZATION AND COLLABORATIVE become very popular for CF. The key idea in MF models is to FILTERING project both user and item representation into the same low- dimensional latent feature space. The rating that a particular We briefly introduce the basics of Matrix Factorization user gives to a catalog item can then be approximated by the (MF). MF has established itself as a mainstream learning inner product of the corresponding user and item vectors in the method for CF recommenders [16], [11]. MF-based methods latent feature space representation. The modeling assumption are increasingly used in large-scale recommendation systems of an underlying low-dimensional subspace is motivated by (e.g., Xbox [17], Azure Recommendations [18], Mahout [19]). the fact that users have affinities for a particular relatively Furthermore, MF-based models for CF have repeatedly demon- small number of item features (e.g. genre, director, lead actor strated better accuracy than other methods such as nearest- in the movie recommendation domain). Factorization of the neighbor models and restricted Boltzmann machines [20], [21]. user-item interaction matrix into the latent space representation MF algorithms are given a description of items and users described above has been widely explored in the literature [11], as input, typically this description takes the form of a sparse [12]. Due to the sparsity of this matrix, traditional methods vector, whose values are either explicit ratings or values for factorization such as Singular Value Decomposition (SVD) inferred from the user data. The output is a set of vectors, yields poor results. Recent works [13], [14] have posed this one for each user and one for each item, spanning a joint user- problem as a regularized regression of available user ratings item latent space. Future user-item