Preventing Manipulation in Aggregating Value-Based Argumentation Frameworks
Grzegorz Lisowski

Abstract:
Recently, connections between abstract argumentation and decision making have gained increasing attention. In particular, value-based argumentation attempts to capture the specificity of deliberation concerning a choice of actions. This approach assumes that in such debates arguments appeal to certain values. Each agent ranks the values and evaluates arguments in accordance with her own preferences over values that they appeal to. The model assumes that an agent disregards attacks on strong arguments by weaker attackers. This move creates agent-specific argumentation frameworks. Another recent line of research in abstract argumentation involves situations in which agents aggregate agents’ views on acceptability of arguments, or on the structure of argumentation.
In the thesis I study strategic behavior in argumentation based on values. The thesis consists of two major parts. The first one considers the single agent scenario. Here, I investigate the possibility for an agent to enforce that an argument supporting her desired decision is accepted when her preference ordering over values does not allow this acceptance. Then, methods of finding the closest preference ordering to the agent’s original hierarchy of values sufficient to achieve this goal are considered.
In the second part I investigate the problem of manipulating the outcome discussion based on values in the multi-agent setting. Here, manipulation is understood as communicating an insincere preference ordering over values to ensure that a desired decision is made. A challenge tackled in this part is concerned with providing a procedure for aggregating opinions about the relative strength of arguments based on values that they appeal to. Two approaches to this problem are considered. In the first of them agents’ preferences over values are aggregated directly with employment of preference aggregation functions. The other approach involves aggregation of argumentation frameworks corresponding to agents’ views on the relative strength of arguments.