Trust is a natural mechanism by which an autonomous party, an agent, can deal with the inherent uncertainty regarding the behaviours of other parties and the uncertainty in the information it shares with those parties. Trust is thus crucial in any decentralised system. This paper builds on recent efforts to use argumentation to reason about trust. Specifically, a set of schemes is provided, and abstract patterns of reasoning that apply in multiple situations geared towards trust. Schemes are described in which one agent, A, can establish arguments for trusting another agent, B, directly, as well as schemes that A can use to construct arguments for trusting C, where C is trusted by B. For both sets of schemes, a set of critical questions is offered that identify the situations in which these schemes can fail.

The interactive ArgTrust application is a decision-making tool that is based on an underlying formal system of argumentation in which the evidence that influences a recommendation, or conclusion, is modulated according to values of trust that the user places in that evidence. This paper presents the design and analysis of a user study which was intended to evaluate the effectiveness of ArgTrust in a collaborative human-agent decision-making task. The results show that users' interactions with ArgTrust helped them consider their decisions more carefully than without using the software tool.

Abstract. Firewalls are an important tool in the assurance of network security. Packet filtering firewalls are configured by providing a set of rules that identify how to handle individual data packets that arrive at the firewall. In large firewall configurations, conflicts may arise between these rules. Argumentation provides a way of handling conflicts such that their origin is illuminated, and hence can help a system administrator understand the effects of a given configuration. To show how argumentation might help in this domain we examine the use of a system of metalevel argumentation for firewall configuration, showing how it makes conflicts and their origins clear, and showing how different instantiations of a metalevel argumentation system provide alternative ways to resolve conflicts.

aspic + is one of the most widely used systems for structured arguments and includes the use of both strict and defeasible rules. Here we consider using just the defeasible part of aspic +. We show that using the resulting system, it is possible, in a well defined sense, to capture the same information as using aspic + with strict rules.