DOCSLIB.ORG

Can Trailers Help to Alleviate Popularity Bias in Choice-Based Preference Elicitation?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Can Trailers Help to Alleviate Popularity Bias in Choice-Based Preference Elicitation? Can Trailers Help to Alleviate Popularity Bias in Choice-Based Preference Elicitation? Mark P. Graus Martijn C. Willemsen Eindhoven University of Technology Eindhoven University of Technology IPO 0.20 IPO 0.17 PB 513, 5600 MB, Eindhoven, Netherlands PB 513, 5600 MB, Eindhoven, Netherlands [email protected] [email protected] ABSTRACT quire them to rely on memory. This can lead to unreliable Previous research showed that choice-based preference elic- feedback [2]. itation can be successfully used to reduce effort during user cold start, resulting in an improved user satisfaction with 1.2 Choice-Based Preference Elicitation the recommender system. However, it has also been shown One way to reduce the effort can be found in choice-based to result in highly popular recommendations. In the present preference elicitation. Where most recommender systems study we investigate if trailers reduce this bias to popular ask users to provide a number of ratings on items (explicit recommendations by informing the user and enticing her feedback), recommender systems applying choice-based pref- to choose less popular movies. In a user study we show erence elicitation ask the user to make a number of choices that users that watched trailers chose relatively less popular (implicit feedback). Using implicit feedback to produce per- movies and how trailers affected the overall user experience sonalized ranking has been shown to provide better fitting with the recommender system. prediction models than using explicit feedback [8]. In recent user studies users of collaborative filtering systems were pro- CCS Concepts vided with choice-based preference elicitation[4, 6]. Where in the more standard rating-based preference elicitation peo- •Information systems ! Recommender systems; •Human-ple are asked to rate the items they know, in choice-based centered computing ! Human computer interaction preference elicitation they are asked to choose the item that (HCI); User studies; User models; best matches there preference from a list. In our own work, this alternative has been shown to require less effort than Keywords more standard rating-based preference elicitation, while al- lowing for more control, resulting in more novel and accurate Recommender Systems; Choice-based Preference Elicitation; recommendations [4]. User Experience; Trailers; Information Other work compared a recommender system using rat- ings against a recommender system using pair-wise compar- 1. INTRODUCTION isons (i.e. choices between two alternatives)[1]. The sys- tem using comparisons provided better recommendations in 1.1 Cold Start terms of objective performance metrics (nDCG and preci- sion). In addition, users preferred the system using pair-wise New user cold start is one of the central problems in rec- comparisons as it made them more aware of their choice op- ommender systems. It occurs when a user starts using a tions and provided a nicer user experience. recommender system. As there is no information for this One observation in [4] was that providing users with the user to base recommendations on, the recommender system possibility to indicate their preferences through choices re- requires her to provide feedback in order to receive recom- sulted in a bias towards more popular movies, and subse- mendations. This requires quite often significant effort of quently users received more popular recommendations. Al- the user. though this experiment showed that popularity leads to higher In addition, as users watch only a certain amount of movies satisfaction at that moment in the lab setting of the study, over any time period, asking users to provide a set amount such popular recommendations may not provide sufficient of feedback may require them to provide feedback on items value in normal, long term usage scenarios. that they have experienced a longer time ago which will re- 1.3 Memory Effects in Recommender Systems Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed Memory effects could be a possible explanation for this for profit or commercial advantage and that copies bear this notice and the full cita- bias towards popular movies that results in people receiv- tion on the first page. Copyrights for components of this work owned by others than ing overly popular recommendations. In rating-based rec- ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or re- publish, to post on servers or to redistribute to lists, requires prior specific permission ommender systems memory effects have been shown to in- and/or a fee. Request permissions from [email protected]. fluence how users provide feedback. Bollen et al.[2] have IntRS 2016, September 16, 2016, Boston, MA, USA. demonstrated that ratings given closer to the time the movie c 2016 ACM. ISBN 123-4567-24-567/08/06. $15.00 was actually watched tend to be more extreme than ratings DOI: 10.475/123 4 for movies that have been watched a longer time ago. They Figure 1: User Interface used for the study. The interface to the left is used for participants in the trailer condition, the interface to the right for participants in the non-trailer condition. Within the interface the list of items to choose from is shown below, the trailer and additional metadata is above. argue that this is because of people forgetting information larity of the items a user chooses. about the movies required to rate them, which has conse- In terms of user experience we expect trailers to provide quences for the reliability of the input provided. This same the user with more information, which is expected to be re- effect could result in users choosing items that they recog- flected in the perceived informativeness of the system. As nize in a choice-based preference elicitation task: it is more we expect trailers to motivate users to select less popular likely that people remember more popular movies than less movies, we expect perceived recommendation novelty (the popular movies. opposite of popularity) and diversity to increase. Both nov- elty and diversity may affect system and choice satisfaction. 1.4 Trailers as source of extra information It is hard to formulate expectations about the direction of The current study tries to investigate if this bias towards the effect of trailers on user satisfaction. We expect user sat- picking popular movies can be alleviated by giving users isfaction in this setting to consist of system satisfaction (i.e. additional information to make more informed choices. \how well does this system help me") and choice satisfaction In order to both minimize the effort required and maxi- (\how happy am I with the item that I choose based on this mize the reliability of the input given during the new user system"). In previous research novelty and system satisfac- cold start situation, we propose to use choice-based pref- tion were shown to be negatively correlated [9, 4]. On the erence elicitation and provide the user with additional in- other hand, trailers might make users open to less popu- formation to give her the means to make more informed lar movies and as such novelty could have a positive effect choices. on choice satisfaction. Additionally previous studies have In most recommender systems users can already rely on shown that system satisfaction positively influences choice meta-information like for example genre, cast and a syn- satisfaction[9]. Having the possibility to watch trailers may opsis. A possible additional source of information about a result in an increased system satisfaction and thus choice movie can be found in trailers. Trailers may help the user in satisfaction. Considering all these effects it is hard to fore- two ways. Firstly, trailers can help a user in refreshing the see in what way trailers will affect user experience. memory to provide reliable feedback, alleviating potential The expected effects are shown in Fig. 2 below, with memory problems described in the previous section. Sec- where possible the directions of the hypothesized effect. ondly, even for movies that a user has not seen yet, a trailer can be used to evaluate whether or not a movie is worth watching. This is an advantage of choice-based preference elicitation over rating-based preference elicitation, because in rating-based users typically only rate (and provide infor- mation on) movies they have actually watched. 1.5 Research Question and hypotheses The present research aims to investigate how providing additional information in the form of trailers during choice- based preference elicitation affects the interaction in terms of both objective behavior and subjective user experience. In terms of objective behavior we hypothesize that trailers allow users to make more informed choices and rely less on Figure 2: Path diagram of expected effects. popularity when making these choices. In other words, we expect the possibility to watch trailers to reduce the popu- Table 1: Texts used for the items in the survey, with item factor loadings and factor robustness per aspect of user experience. Considered As- Item Factor Loading pect I got sufficient information on each movie to make a choice. Informativeness Visual information is more important to me for making a choice than written AVE = 0.587 information. α = 0:71 I like the way information about the movies is provided to me in this system. 0.936 The system provided too much information for each movie. I would rather have different information about the movies than what I got -0.647 from the system to make a choice The recommendations contained a lot of variety. Diversity The recommendations covered many movie genres. AVE: 0.655 All the recommended movies were similar to each other. 0.822 α = 0:80 Most movies were from the same genre.
Load more

Recommended publications
  • Learning Preferences of New Users in Recommender Systems: an Information Theoretic Approach
    Learning Preferences of New Users in Recommender Systems: An Information Theoretic Approach Al Mamunur Rashid, George Karypis, and John Riedl Department of Computer Science & Engineering, University of Minnesota, Minneapolis, MN-55455 {arashid, karypis, riedl}@cs.umn.edu Abstract. Recommender systems are a nice tool to help nd items of interest from an overwhelming number of available items. Collaborative Filtering (CF), the best known technology for recommender systems, is based on the idea that a set of like-minded users can help each other nd useful information. A new user poses a challenge to CF recommenders, since the system has no knowledge about the preferences of the new user, and therefore cannot provide personalized recommendations. A new user preference elicitation strategy needs to ensure that the user does not a) abandon a lengthy signup process, and b) lose interest in returning to the site due to the low quality of initial recommendations. We extend the work of [23] in this paper by incrementally developing a set of in- formation theoretic strategies for the new user problem. We propose an oine simulation framework, and evaluate the strategies through exten- sive oine simulations and an online experiment with real users of a live recommender system. 1 Introduction Collaborative Filtering (CF)-based recommender systems generate recommen- dations for a user by utilizing the opinions of other users with similar taste. These recommender systems are a nice tool bringing mutual benets to both users and the operators of the sites with too much information. Users benet as they are able to nd items of interest from an unmanageable number of available items.
    [Show full text]
  • Preference Elicitation Techniques for Group Recommender Systems ⇑ Inma Garcia , Sergio Pajares, Laura Sebastia, Eva Onaindia
    Information Sciences xxx (2011) xxx–xxx Contents lists available at SciVerse ScienceDirect Information Sciences journal homepage: www.elsevier.com/locate/ins Preference elicitation techniques for group recommender systems ⇑ Inma Garcia , Sergio Pajares, Laura Sebastia, Eva Onaindia Universitat Politècnica de València, Camino de Vera s/n, E46022 Valencia, Spain article info abstract Article history: A key issue in group recommendation is how to combine the individual preferences of dif- Received 31 January 2011 ferent users that form a group and elicit a profile that accurately reflects the tastes of all Received in revised form 18 October 2011 members in the group. Most Group Recommender Systems (GRSs) make use of some sort Accepted 26 November 2011 of method for aggregating the preference models of individual users to elicit a recommen- Available online xxxx dation that is satisfactory for the whole group. In general, most GRSs offer good results, but each of them have only been tested in one application domain. Keywords: This paper describes a domain-independent GRS that has been used in two different Group recommender systems application domains. In order to create the group preference model, we select two tech- Group profile Preference elicitation niques that are widely used in other GRSs and we compare them with two novel tech- niques. Our aim is to come up with a model that weighs the preferences of all the individuals to the same extent in such a way that no member in the group is particularly satisfied or dissatisfied with the final recommendations. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction A Recommender System (RS) [52] is a widely used mechanism for providing advice to people in order to select a set of items, activities or any other kind of product.
    [Show full text]
  • Diverse User Preference Elicitation with Multi-Armed Bandits
    Session 3: Recommender Systems WSDM ’21, March 8–12, 2021, Virtual Event, Israel Diverse User Preference Elicitation with Multi-Armed Bandits Javier Parapar∗ Filip Radlinski [email protected] [email protected] Universidade da Coruña Google Research A Coruña, Spain London, United Kingdom ABSTRACT 1 INTRODUCTION Personalized recommender systems rely on knowledge of user pref- Recommender Systems (RSs) [46] have become ubiquitous for rec- erences to produce recommendations. While those preferences are ommending movies [19], music [54], books [57], news [34], and in often obtained from past user interactions with the recommenda- numerous other domains. Their goal is to help users more quickly tion catalog, in some situations such observations are insufficient find relevant items in vast catalogues. or unavailable. The most widely studied case is with new users, One of the most common approaches is Collaborative Filtering although other similar situations arise where explicit preference (CF), which depends on rich user preference information to discover elicitation is valuable. At the same time, a seemingly disparate relationships between items, and in turn allows user-user and item- challenge is that there is a well known popularity bias in many al- item similarity to be estimated. Given a user profile, items of interest gorithmic approaches to recommender systems. The most common to similar users can then be suggested. Preferences can be explicit way of addressing this challenge is diversification, which tends to (for example, ratings on books, or likes of posts) or implicit (for be applied to the output of a recommender algorithm, prior to items example, the history of songs a user has listened to, or films the user being presented to users.
    [Show full text]
  • Leveraging Collective Intelligence in Recommender System
    Leveraging Collective Intelligence in Recommender System A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Shuo Chang IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy Loren G Terveen August, 2016 c Shuo Chang 2016 ALL RIGHTS RESERVED Acknowledgements Through the five years of my graduate school, I have received numerous support from my family, friends and colleagues. This thesis would not have been possible without them. First and foremost, I thank my advisor Dr. Loren Terveen for sharing his wisdom and helping me to grow. He gave me the freedom to pursue my research interest and challenge me to be better. During difficult times, he consuls me with his kindness and patience. I am forever grateful for what I have learned from him during this five years. I would also like to thank my committee members | Dr. Joseph Konstan, Dr. George Karypis and Dr. Yuqing Ren | for providing valuable feedback. I thank Ed Chi, Peng Dai and Elizabeth Churchill for giving me internship oppor- tunities and being awesome mentors. During the internships, I was fortunate to receive guidance and support from Atish Das Sarma, Lichan Hong, Jilin Chen and Zhiyuan Cheng. I am very thankful to be a member of the GroupLens research lab, which will always have a special place in my heart. I'd like to thank Dr. John Riedl for welcoming me to the GroupLens family. I truly enjoyed working and being friend with Max Harper, Vikas Kumar, Daniel Kluver, Tien Nguyen, Hannah Miller, Jaccob Thebault-Spieker, Aditya Pal, Isaac Johnson, Qian Zhao, Dr.
    [Show full text]
  • Preference Elicitation and Negotiation in a Group Recommender System Jesús Álvarez Márquez, Jurgen Ziegler
    Preference Elicitation and Negotiation in a Group Recommender System Jesús Álvarez Márquez, Jurgen Ziegler To cite this version: Jesús Álvarez Márquez, Jurgen Ziegler. Preference Elicitation and Negotiation in a Group Recom- mender System. 15th Human-Computer Interaction (INTERACT), Sep 2015, Bamberg, Germany. pp.20-37, 10.1007/978-3-319-22668-2_2. hal-01599849 HAL Id: hal-01599849 https://hal.inria.fr/hal-01599849 Submitted on 2 Oct 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License Preference Elicitation and Negotiation in a Group Recommender System Jesús Omar Álvarez Márquez1, Jürgen Ziegler1 1University of Duisburg-Essen, Duisburg, Germany {jesus.alvarez-marquez, juergen.ziegler}@uni-due.de Abstract. We present a novel approach to group recommender systems that better takes into account the social interaction in a group when formulating, dis- cussing and negotiating the features of the item to be jointly selected. Our ap- proach provides discussion support in a collaborative preference elicitation and negotiation process. Individual preferences are continuously aggregated and immediate feedback of the resulting recommendations is provided. We also support the last stage in the decision process when users collectively select the final item from the recommendation set.
    [Show full text]
  • Eliciting Pairwise Preferences in Recommender Systems
    Eliciting Pairwise Preferences in Recommender Systems Saikishore Kalloori, Francesco Ricci and Rosella Gennari Free University of Bozen - Bolzano, Italy Piazza Domenicani 3, I - 39100, Bolzano, Italy [email protected],[email protected],[email protected] ABSTRACT from absolute item evaluations, e.g., user ratings or likes [31]. How- Preference data in the form of ratings or likes for items are widely ever, this type of preferences have few disadvantages, illustrated in used in many Recommender Systems. However, previous research previous literature [5, 22, 23]. For instance, if a user has assigned has shown that even item comparisons, which generate pairwise the highest rating to an item and, subsequently, the user nds that preference data, can be used to model user preferences. Moreover, he prefers another item to the rst one, the user has no choice but pairwise preferences can be eectively combined with ratings to to also give to this new item the highest rating [11]. Moreover, if compute recommendations. In such hybrid approaches, the Rec- most of the items are rated with the largest rating, then it is dicult ommender System requires to elicit both types of preference data to understand which items the user does like the most. from the user. In this work, we aim at identifying how and when to For such reasons, few researchers [5, 11, 22] have developed elicit pairwise preferences, i.e., when this form of user preference recommendation techniques that leverage an alternative way to data is more meaningful for the user to express and more benecial collect user preferences, namely, pairwise comparisons, such as for the system.
    [Show full text]
  • Eliciting Worker Preference for Task Completion
    Eliciting Worker Preference for Task Completion Mohammad Esfandiari #1, Senjuti Basu Roy #1, Sihem Amer-Yahia ∗2 # NJIT, USA 1 [email protected], [email protected] ∗ Univ. Grenoble Alpes, CNRS, LIG, France 2 [email protected] Abstract—Current crowdsourcing platforms provide little sup- In this paper, our objective is to design a framework that port for worker feedback. Workers are sometimes invited to advocates for explicit preference elicitation from workers to post free text describing their experience and preferences in develop a model that guides task completion. That differs completing tasks. They can also use forums such as Turker Nation1 to exchange preferences on tasks and requesters. In fact, from developing solutions for task assignment. The objective crowdsourcing platforms rely heavily on observing workers and behind preference elicitation is to use obtained feedback to inferring their preferences implicitly. In this work, we believe effectively maintain a Worker Model. Given a task t that a that asking workers to indicate their preferences explicitly improve worker w undertakes (either via self-appointment or via an their experience in task completion and hence, the quality of their assignment algorithm), there could be one of two possible contributions. Explicit elicitation can indeed help to build more accurate worker models for task completion that captures the outcomes : 1. the task is completed successfully. 2. otherwise. evolving nature of worker preferences. We design a worker model In reality, worker preferences are latent, i.e., they are to whose accuracy is improved iteratively by requesting preferences be inferred through task factors and task outcomes.
    [Show full text]
  • Towards Conversational Recommender Systems
    Towards Conversational Recommender Systems Konstantina Christakopoulou⇤ Filip Radlinski, Katja Hofmann University of Minnesota Microsoft United States Cambridge, UK [email protected] {filiprad, katja.hofmann}@microsoft.com ABSTRACT users by the characteristics of the items they like or dislike. People often ask others for restaurant recommendations as a We note that neither model represents how real people make way to discover new dining experiences. This makes restau- recommendations, particularly in a cold-start setting where rant recommendation an exciting scenario for recommender the person making a recommendation does not know a lot systems and has led to substantial research in this area. about the person asking for one. However, most such systems behave very di↵erently from Consider what would happen if a conference attendee in a human when asked for a recommendation. The goal of your home town, whom you have never met before, asked this paper is to begin to reduce this gap. for a recommendation on where to eat dinner today. Most In particular, humans can quickly establish preferences likely, you would start with one or two clarifying questions, when asked to make a recommendation for someone they do perhaps whether the person likes seafood, or whether they not know. We address this cold-start recommendation prob- have a car. These questions would depend on the context; lem in an online learning setting. We develop a preference for instance if there are great restaurants around the corner, elicitation framework to identify which questions to ask a then whether they have a car would be irrelevant. new user to quickly learn their preferences.
    [Show full text]
  • Mining Large Streams of User Data for Personalized Recommendations
    Mining Large Streams of User Data for Personalized Recommendations Xavier Amatriain Netflix xamatriain@netflix.com ABSTRACT solutions - think, for example, of ranking metrics such as Normalized Discounted Cumulative Gain (NDCG) or other The Netflix Prize put the spotlight on the use of data min- information retrieval ones such as recall or area under the ing and machine learning methods for predicting user pref- curve (AUC). Beyond the optimization of a given offline met- erences. Many lessons came out of the competition. But ric, what we are really pursuing is the impact of a method on since then, Recommender Systems have evolved. This evo- the business. Is there a way to relate the goodness of an algo- lution has been driven by the greater availability of different rithm to more customer-facing metrics such as click-through kinds of user data in industry and the interest that the area rate (CTR) or retention? I will describe our approach to in- has drawn among the research community. The goal of this novation called \Consumer Data Science" in section 3.1. paper is to give an up-to-date overview of the use of data mining approaches for personalization and recommendation. But before we understand the reasons for all these effects, Using Netflix personalization as a motivating use case, I will and before we are ready to embrace the open research ques- describe the use of different kinds of data and machine learn- tions in the area of personalization described in Section 5, ing techniques. we need to understand some of the basic techniques that enable the different approaches.
    [Show full text]
  • User Preference Elicitation, Rating Sparsity and Cold Start: Algorithms, Practical Challenges and Applications
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/329398751 User Preference Elicitation, Rating Sparsity and Cold Start: Algorithms, Practical Challenges and Applications Chapter · November 2018 DOI: 10.1142/9789813275355_0008 CITATIONS READS 11 432 4 authors: Mehdi Elahi Matthias Braunhofer University of Bergen Microsoft 85 PUBLICATIONS 1,490 CITATIONS 28 PUBLICATIONS 628 CITATIONS SEE PROFILE SEE PROFILE Tural Gurbanov Francesco Ricci ivi.ru Free University of Bozen-Bolzano 9 PUBLICATIONS 47 CITATIONS 284 PUBLICATIONS 12,743 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Music recommender systems View project Create new project "ONE Project" View project All content following this page was uploaded by Mehdi Elahi on 21 March 2019. The user has requested enhancement of the downloaded file. May 24, 2018 18:12 ws-book9x6 Collaborative Recommendations: Algorithms, Practical Challenges and Applications 08preferenceelicitation page 1 Chapter 1 User preference elicitation, rating sparsity and cold start Mehdi Elahi, Matthias Braunhofer, Tural Gurbanov, Francesco Ricci Free University of Bozen - Bolzano, Piazza Domenicani, 3 Italy - 39100, Bozen-Bolzano meelahi,mbraunhofer,tgurbanov,fricci @unibz.it { } 1.1 Abstract A prerequisite for implementing collaborative filtering recommender sys- tems is the availability of users’ preferences data. This data, typically in the form of ratings, is exploited to learn the tastes of the users and to serve them with personalized recommendations. However, there may be a lack of preference data, especially at the initial stage of the operations of a recommender system, i.e., in the Cold Start phase.
    [Show full text]
  • Preference Elicitation by Solving the Cold Start Problem
    International Journal of Latest Research in Engineering and Technology (IJLRET) ISSN: 2454-5031 www.ijlret.com || Volume 02 - Issue 05 || May 2016 || PP. 100-107 Preference Elicitation by Solving the Cold Start Problem Jaswanth Kannan, R1, Karthiga, S2, Manivel, S3 1,3Student, 2AssistantProfessor Department of Information Technology, Thiagarajar College of Engineering, Madura Abstract— There is an extensive class of Web applications that involve predicting user responses to options. Such a facility is called a recommendation system. A specific example of recommendation systems is to offer customers a non-line retailer suggestions about what they might like to buy, based on past history of purchases and/ or product searches. Cold start is a potential problem in computer-based information systems which involve a degree of automated data modeling. Specifically, it concerns the issue that the system cannot draw any inferences for users or items about which it has not yet gathered sufficient information. The cold start problem is most prevalent in recommender systems. Typically, are commander system compares the user's profile to some reference characteristics. These characteristics may be from the information item (the content-based approach) or the user's social environment (the collaborative filtering approach). Preference elicitation is a decision support system capable of generating recommendations to a user, thus assisting in decision making. It gives preferences accurately, finds hidden preferences and avoids redundancy. Index Terms — Recommender System, Big Data, Neo4j tool, Graph. I. INTRODUCTION Big data analysis is one of the upcoming disciplines in data mining where the large unstructured data that is very difficult to store and retrieve in an efficient manner.
    [Show full text]
  • Negotiation and Reconciliation of Preferences in a Group Recommender System
    Journal of Information Processing Vol.26 186–200 (Feb. 2018) [DOI: 10.2197/ipsjjip.26.186] Regular Paper Negotiation and Reconciliation of Preferences in a Group Recommender System Jesus´ Omar A´ lvarez Marquez´ 1,a) Jurgen¨ Ziegler1,b) Received: May 24, 2017, Accepted: November 7, 2017 Abstract: This article presents an approach to group recommender systems that focuses its attention on the group’s social interaction during the formulation, discussion and negotiation of the features the item to be jointly selected should possess. Current group recommender techniques are mainly based on aggregating existing user profiles or on a profile of the group as a whole. Our method supports collaborative preference elicitation and negotiation process where desired features have to be chosen individually, but group consensus is needed for them to become active in the item filtering process. Users provide feedback on the selected preferences and change their significance, bringing up new recommendations each time individual settings are modified. The last stage in the decision process is also sup- ported, when users collectively select the final item from the recommendation set. We explored the possible benefits of our approach through the development of three prototypes, each based on a different variant of the approach with adifferent emphasis on private and group-wide preference spaces. They were evaluated with user groups of different size, addressing questions regarding the effectiveness of different information sharing methods and the repercussion of group size in the recommendation process. We compare the different methods and consolidate the findings in an initial model of recommending for group. Keywords: group recommender system, group preference elicitation, negotiation, decision-making ample, when jointly going to a restaurant or to the movies.
    [Show full text]