Supporting a Group Member to Make a Group Choice Hanif Emamgholizadeh hemamgholizadeh@unibz.it Free University of Bozen Bolzano Bolzano, Bolzano, Italy Amra Delic adelic@etf.unsa.ba University of Sarajevo Sarajevo, Bosnia and Herzegovina Francesco Ricci francesco.ricci@unibz.it Free University of Bozen Bolzano Bolzano, Bolzano, Italy Abstract We often make choices that involve a group of people, such as selecting a movie to watch with friends or choosing a travel desti- nation to visit with the family. Sometimes, a single member of the group may be in charge of making the decision for the group, by playing the role of łorganizerž. Although some tools for supporting Group Decision-Making have been proposed, none of them have considered the case where a single group member is autonomously making such a decision, hence entering the preferences of the group members, interacting with the system, and fnally selecting a proper recommendation. In this paper, we introduce MyFoodGRS, a web application for a single user to fnd a proper restaurant for their group, that supports the previously mentioned tasks. We introduce an interaction design to follow the Attribute and Socially-based group decision patterns, and we report the positive result of the conducted system usability evaluation. Keywords Recommender Systems, Group Recommender Systems, Decision Making, Group Decision Making ACM Reference Format: Hanif Emamgholizadeh, Amra Delic, and Francesco Ricci. 2023. Supporting a Group Member to Make a Group Choice. In UMAP ’23 Adjunct: Adjunct Proceedings of the 31st ACM Conference on User Modeling, Adaptation and Personalization (UMAP ’23 Adjunct), June 26ś29, 2023, Limassol, Cyprus. ACM, New York, NY, USA, 4 pages. https://doi.org/10.1145/3563359.3597414 1 Introduction There are some circumstances in which a group of users may need to fnd a proper product or service to be consumed jointly by the group. For instance, when a group of close friends wants to go on a trip and they need to assemble a travel plan to satisfy the preferences of all of them, or when a person wants to invite their colleagues to a restaurant. To address these needs, Group Recommender sys- tems (GRS) have been employed [7]. GRS leverage techniques that aid a group in their decision-making activities by suggesting perti- nent items or facilitating them in a joint Group Decision Making (GDM) process [7]. In the majority of the cases where a GRS is employed, either all or some of the group members are actively involved, e.g., in eliciting preferences and negotiating. However, there are certain scenarios where a single member of the group Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for proft or commercial advantage and that copies bear this notice and the full citation on the frst page. Copyrights for third-party components of this work must be honored. For all other uses, contact the owner/author(s). UMAP ’23 Adjunct, June 26ś29, 2023, Limassol, Cyprus © 2023 Copyright held by the owner/author(s). ACM ISBN 978-1-4503-9891-6/23/06. https://doi.org/10.1145/3563359.3597414 makes a decision on behalf of the entire group. In such cases, this individual (henceforth referred to as the organizer) is uniquely responsible for making the decision. For instance, if someone wants to invite their colleagues to a restaurant, they may try to search for a venue that fts all the group members, and make a surprise. This type of decision-making is a particular case of GDM that, despite the absence of the preference elicitation and options’ discussion steps, is not necessarily simpler. Remembering each invitee’s food preferences and possible dietary restrictions, striving to balance the satisfaction level of all participants, and maximizing the group’s overall satisfaction are some of the challenges that the organizer will encounter. Since the frst GRS application was introduced [9], a number of follow up techniques have been proposed to support groups in their Decision Making (DM) process [1, 10, 12]. Of particular interest for this work are INTRIGUE [2] and REMPAD [3], which were properly designed to aid the organizer of an event. INTRIGUE is a GRS that allows the tour leader to input the group members’ information. On the base of those preferences, recommendations are generated, specifcally tailored to satisfy a number of homogeneous subgroups in the larger and heterogeneous group of people. REMPAD facili- tates the organizer of a group of a reminiscence therapy session in selecting appropriate multimedia content. Providing assistance to an event organizer in selecting an ap- propriate restaurant involves diferent domain-dependent function- alities. For instance, in contrast to an itinerary recommendation problem, where there are various points of interest (POIs) that can be suggested to a group to ensure that each group member is enough satisfed, it can be challenging to fnd a single restaurant that is suitable for groups with diverse preferences. Additionally, unlike in the reminiscence therapy application [3], the organizer may only have limited knowledge about the favorite dishes of each member in the group. We note that while most of the commercial restaurant fnders, like TripAdvisor (https://www.tripadvisor.com/), are meant to be used by a single person, eventually on behalf of a group, they do not ofer explicit support for GDM. As a solution to these problems, we propose MyFoodGRS (http://myfoodgrs.inf.unibz.it:8080/), an application that can assist event organizers in fnding a suitable restaurant for a group. In this paper, we introduce MyFoodGRS that we developed in collabora- tion with okkam.it. MyFoodGRS provides a set of group-oriented functionalities that enable organizers to assess the relative qual- ity of restaurants, reconcile the diverse preferences of the group members, and make informed decisions by using the attribute- and the socially-based choice patterns. We have evaluated MyFoodGRS by using the SUS usability questionnaire [4] and obtained a score higher than the benchmark. The usability study also indicated that organizers more often adopt the attribute-based choice pattern, when they are making a restaurant decision for the group. 96