MENTOR: A graphical monitoring tool of preferences evolution in large-scale group decision making

Group decision making problems aim to manage situations in which two or more experts need to achieve a common solution to a decision problem. Different rules and processes can be applied to solve such problems (e.g. majority rule, consensus reaching, and so on), and several models have been proposed to deal with them. Some difficulties may arise in group decisions, being most of them caused by the presence of disagreement positions amongst experts. Given that group decision making problems have classically focused on a few number of experts, such difficulties have been relatively manageable by means of supporting tools based on textual or numerical information. However, such tools are not adequate when a large number of experts take part in the problem, therefore an alternate tool that provides decision makers with more easily interpretable information about the status of the problem becomes necessary. This paper proposes a graphical monitoring tool based on Self-Organizing Maps so-called MENTOR, that provides a 2-D graphical interface whose information is related to experts' preferences and their evolution during group decision making problems, and facilitates the analysis of information about large-scale problems. Decision Making is a common process in daily life. In Group Decision Making (GDM) problems, two or more individuals or experts , with their own attitudes and opinions, need to achieve a common solution to a decision problem consisting of several alternatives [1–3]. GDM problems are present in diverse application areas that require the participation of multiple experts, such as management and engineering and politics [4–6]. GDM problems can be solved by applying different processes, ranging from the use of classical decision rules (such as the majority or minority rule [7]), to the application of a consensus reaching process, which is a process of negotiation between experts, aimed to achieve a high level of agreement in the group before making a decision [8]. Consensus reaching processes are increasingly necessary in nowadays group decisions [9]. A large number of theoretical models and approaches to facilitate the resolution of GDM problems have been proposed in the literature [3,10–14]. Moreover, several authors have developed some computer-based Group Decision Support Systems (GDSS), to give groups further assistance in such problems [3,15]. Some of these GDSS make use of the Internet to allow groups to solve GDM problems ubiquitously [16,17]. Classically, GDM problems have been solved by a few number of experts. In these cases, when typical difficulties in …