Personalization of Web Search using Social Signals ∗ Ali Khodaei Sina Sohangir Cyrus Shahabi Yahoo! Corporation GraphDive Company Department of Computer 701 1st Ave. 1295 El Camino Real, Suite B Science Sunnyvale,CA 94089,USA Menlo Park, CA 94025 University of Southern [email protected] [email protected] California Los Angeles,CA 90089,USA [email protected] ABSTRACT For instance, [3] proposed a search engine that combines tra- Over the last few years, Web has changed significantly. Emer- ditional content-based search with context information gath- gence of social networks and Web 2.0 have enabled people to ered from user's activities. More recently, search engines interact with web document in new ways not possible before. started to make the search results more personalized. With In this paper, we present PERSOSE a new search engine personalized searches, search engines consider the searcher's that personalizes the search results based on user's social preferences, interests, behavior and history. The final goal actions. Although the users social actions may sometimes of personalized search as well as other techniques studying seem irrelevant to the search, we show that they are actu- users' preferences and interests is to make the returned re- ally useful for personalization. We propose a new relevance sults more relevant to what the user is actually looking for. model called persocial relevance model utilizing three levels Emergence of social networks on the web (e.g., Facebook of social signals to improve the web search. We show how and Google Plus)have caused the following key changes on each level of persocial model (user's social actions, friends' the web. First, social networks reconstruct friendship net- social actions and social expansion) can be built on top of works in the virtual world of the web. Many of these virtual the previous level and how each level improves the search relationships are good representatives of their actual (friend- results. Furthermore, we develop several approaches to in- ship) networks in the real world. Second, social networks tegrate persocial relevance model into the textual web search provide a medium for users to express themselves and freely process. We show how PERSOSE can run effectively on 14 write about their opinions and experiences. The social data million Wikipedia articles and social data from real Face- generated for each user is a valuable source of information book users and generate accurate search results. Using PER- about that user's preferences and interests. Third, social SOSE, we performed a set of experiments and showed the networks create user identifiers (identities) for people on the superiority of our proposed approaches. We also showed web. Users of a social network such as Facebook will have how each level of our model improves the accuracy of search a unique identity that can be used in many places on the results. web. Not only such users can use their Facebook identities on the social network itself but they can also use that iden- tity to connect and interact with many other web-sites and 1. INTRODUCTION applications on the web. Along the same lines, social net- While in early stages, search engines' focus was mainly on works such as Facebook and Google Plus provide utilities searching and retrieving relevant document based on their for other web-sites to get integrated with them directly, en- content (e.g., textual keywords), new search engines and new abling users of the social network to interact directly with studies start to focus on context alongside content as well. those web-sites and web documents using their social net- work identity. For instance, a web document can be inte- ∗This research has been funded in part by Award No. 2011- grated into Facebook (using either Facebook Connect or in- IJCX-K054 from the National Institute of Justice, Office 1 of Justice Programs, U.S. Department of Justice, as well stant personalization ) allowing every Facebook user to per- as NSF grant IIS-1320149, the USC Integrated Media Sys- form several actions (e.g., LIKE, RECOMMEND, SHARE) tems Center (IMSC) and unrestricted cash gifts from Google on that document. Finally, many search engines are starting and Northrop Grum- man. Any opinions, findings, and con- to connect to social networks and allows users of such social clusions or recommendations expressed in this material are networks to be the users of the search engine. For instance, those of the authors and do not necessarily reflect the views of any of the sponsors such as the National Science Founda- the Bing search engine is connected to Facebook and hence tion or the Department of Justice. users with their Facebook identities can log-in into Bing to perform their searches. The above developments inspired us to study a new frame- work for search personalization. In this paper, we propose a new approach for performing personalized search using Permission to make digital or hard copies of all or part of this work for users' social actions (activities) on the web. We utilize the personal or classroom use is granted without fee provided that copies are new social information mentioned above (user's social activ- not made or distributed for profit or commercial advantage and that copies ities, friendships, user identities and interaction of users on bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific web documents) to personalize the search results generated permission and/or a fee. 1 Copyright 20XX ACM X-XXXXX-XX-X/XX/XX ...$15.00. https://developers.facebook.com/docs/guides/web/ for each user. We call this new approach to personaliza- are often well-connected to each other. We argue that so- tion of search, persocialized search since it uses social signals cial features of each document should be dynamic, meaning to personalize the search. While a traditional personalized that social actions/signals of the document can and should search maintains information about the users and the his- be propagated to other adjacent documents. A user's inter- tory of their interactions with the system (search history, est for a document - shown by a social action such as LIKE query logs), a persocialized search system maintains infor- - can often imply the user's interests in other relevant docu- mation about the users, their friendships (relations) with ments - often connected to the original document. Thus, we other users and their social interactions with the documents use connections among documents to let social scores flow (via social actions). among documents, hence generating a larger document set Recently, [39] conducted a complete survey on the topic with more accurate persocial relevance scores for each user. of social search and various existing approaches to conduct In sum, the major contribution of this paper is to pro- social search. As mentioned in [39] there exist several defini- pose a model and build a system for utilizing users' social tions for social search: One definition is the way individuals actions to personalize the web search. We propose a new rel- make use of peers and other available social resources dur- evance model to capture relevance between documents and ing search tasks [21]. Similarly, [22] defines social search as users based on users' social activities. We model three levels using the behavior of other people to help navigate online, of personalization based on three sets of social signals and driven by the tendency of people to follow other people's show how each level improves the web search personaliza- footprints when they feel lost. A third definition is by [23] tion. In addition, we propose three new ranking approaches and is defined as searching for similar-minded users based on to combine the textual and social features of documents and similarity of bookmarks. Finally, [24]'s definition of social users. Furthermore, we develop a persocialized search engine search includes a range of possible social interactions that dubbed persocialized search engine ('PERSOSE' for short) may facilitate information seeking and sense-making tasks: to perform persocialized search on real data using real users. utilizing social and expertise networks; employing shared so- Using PERSOSE, we conduct a comprehensive set of exper- cial work spaces; or involving social data-mining or collective iments using 14 million documents of Wikipedia as our doc- intelligence processes to improve the search process. For us, ument set and real Facebook users as our users. As a result social search focuses on utilizing querying user's as well as of the experiments, we show that social actions of a user, her friends' social actions to improve the conventional tex- his friends' social actions and social expansion of documents tual search. By integrating these social actions/signals into (all three levels of social signals) improve the accuracy of the textual search process, we define a new search mech- search results. anism: persocialized search. Our main goal in this paper is to prove our hypothesis that these social actions (from 2. OVERVIEW the querying user and his friends) are relevant and useful to In this section, we present the problem statement without improve the quality of the search results. going into much details (we present some of definitions/formalizations Towards this end, we propose a new relevance model called in Section 3.1). We also provide the system overview of the persocial relevance model to determine the social rele- PERSOSE. vance between a user and a document. Persocial model is The objective of PERSOSE search engine can be stated developed in three levels, where each level complements the as follows: previous level. First, we are using social actions of a user on Suppose D = fd ,d ,...,d g is the set of documents that documents as implicit judgment/rating of those documents 1 2 n exist in our system.