A Voting Argumentation Framework: Considering the Reasoning behind Preferences

International audienceOne of the most prominent ways to reach an acceptable collective decision in normal group settings is the employment of routines and methods of social choice theory. The classical social choice setting is the following: each agent involved in the decision expresses her preferences about a given set of alternatives in the form of a linear order on them. Then, the group's aggregated decision is the outcome of the application of a voting rule to the input's preferences. However, there are instances where social choice on its own cannot provide proper solutions. For example, there are decision problems where the outcome has to be based on the reasoning behind agents' preferences, rather than the unjustified preferences itself. Hence, our research motivation is the practical case where agents' rationale is needed for the decision outcome. In this paper, we explore how the agents' rationale can be formulated inside the classical voting setting. Therefore, we propose a decision-making procedure based on argumenta-tion and preference aggregation which permits us to explore the effect of reasoning and deliberation along with voting for the decision process. We quantify the deliberation phase by defining a new voting argumentation framework, that uses vote and generic arguments, and its acceptability semantics based on the notion of pairwise comparisons between alternatives. We prove for these semantics some theoretical results regarding well-known properties from Argumentation and Social Choice Theory