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Copyright of Research & Development in Intelligent Systems XXIV is the property of Springer eBooks and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In our previous work on dialogue games for agent interaction, an agent's set of beliefs (Σ) and an agent's "commitment store" (CS) — the set of locutions uttered by the agent — play a crucial role. The usual assumption made in this work is that the set of beliefs is static through the course of a dialogue, while the commitment store is dynamic. While the assumption of static beliefs is reasonable during the progress of the dialogue, it seems clear that some form of belief change is appropriate once a dialogue is complete. What form this change should take is our subject in this paper. [ABSTRACT FROM AUTHOR]

Disseminating pieces of knowledge among the members of large organizations is a well known problem in Knowledge Management, involving several decision-making processes. The JITIK multiagent framework has been successfully used for just-in-time delivering highly customized notifications to the adequate users in large distributed organizations. However, in JITIK as well as in other similar approaches it is common to deal with incomplete information and conflicting policies, making difficult to make decisions about whether to deliver or not a specific piece of information or knowledge on the basis of a rationally justified procedure. This paper presents an approach to cope with this problem by integrating JITIK with a defeasible argumentation formalism. Conflicts among policies are solved on the basis of a dialectical analysis whose outcome determines whether a particular information item should be delivered to a specific user. Keywords: Argumentation, knowledge management, information systems. [ABSTRACT FROM AUTHOR]

This paper aims at proposing a general formal framework for dialogue between autonomous agents which are looking for a common agreement about a collective choice. The proposed setting has three main components: the agents, their reasoning capabilities, and a protocol. The agents are supposed to maintain beliefs about the environment and the other agents, together with their own goals. The beliefs are more or less certain and the goals may not have equal priority. These agents are supposed to be able to make decisions, to revise their beliefs and to support their points of view by arguments. A general protocol is also proposed. It governs the high-level behaviour of interacting agents. Particularly, it specifies the legal moves in the dialogue. Properties of the framework are studied. This setting is illustrated on an example involving three agents discussing the place and date of their next meeting. Keywords: Argumentation, Negotiation. [ABSTRACT FROM AUTHOR]

A key goal for a scientist is to find evidence to argue for or against universal statements (in effect first-order formulae) about the world. Building logic-based tools to support this activity could be potentially very useful for scientists to analyse new scientific findings using experimental results and established scientific knowledge. In effect, these logical tools would help scientists to present arguments and counterarguments for tentative scientific knowledge, and to share and discuss these with other scientists. To address this, in this paper, we explain how tentative and established scientific knowledge can be represented in logic, we show how first-order argumentation can be used for analysing scientific knowledge, and we extend our framework for evaluating the degree of conflict arising in scientific knowledge. We also discuss the applicability of recent developments in optimizing the impact and believability of arguments for the intended audience. [ABSTRACT FROM AUTHOR]

This paper presents an argumentation-based approach to deliberation, the process by which two or more agents reach a consensus on a course of action. The kind of deliberation that we are interested in is a process that combines both the selection of an overall goal, the reduction of this goal into sub-goals, and the formation of a plan to achieve the overall goal. We develop a mechanism for doing this, describe how this mechanism can be integrated into a system of argumentation to provide a sound and complete deliberation system, and show how the same process can be achieved through a multi-agent dialogue. [ABSTRACT FROM AUTHOR]

Autonomous agents working in multi-agent environments need to cooperate in order to fulfill tasks. Generally, an agent cannot perform a task alone and needs help from the other agents. One of the solutions to this problem is to look for groups of agents which are able to perform the desired tasks better. Different algorithms have then been proposed for the task allocation via coalition formation. This last is generally seen as a two steps process: i) constructing the different solutions (called coalitions structures), then ii) discussing these solutions between the agents in order to select the best ones which will be adopted. This paper provides a unified formal framework for constructing the coalitions structures. In fact, we will show that the problem of coalition formation can be defined in terms only of a set of coalitions whose structures are abstract, a conflict relationship between the coalitions and a preference relation between the coalitions. Three semantics for coalitions structures will be proposed: a basic semantics which will return a unique coalition structure, stable semantics and preferred semantics. These two last may return several coalitions structures at the same time. A proof theory of the basic semantics will also be proposed. The aim of this proof theory is to test whether a given coalition will be acceptable for the agent or not without computing the whole structure. We will show that this framework is general enough to capture different propositions made in the literature. An instantiation of our framework is given and its properties are studied. [ABSTRACT FROM AUTHOR]

Inspired by computational linguistic approaches to annotate the structures that occur in human dialogue, this paper describes a technique which encodes these structures as transformations applied to a protocol language. Agents can have a controlled and verifiable mechanism to synthesise and communicate their interaction protocol during their participation in a multiagent system. This is in contrast to the approaches where agents must subscribe to a fixed protocol and relinquish control over an interaction that may not satisfy the agent's dialogical needs or rely on internal its reasoning to determine which message to communicate at a certain point in the dialogue. [ABSTRACT FROM AUTHOR]

This paper proposes a liberalized version of existing truth-finding protocols for argumentation, such as the standard two-agent immediate-response protocol for computing the credulous acceptance of conclusions in an argument system. In the new setup agents decide autonomously which issues need to be discussed, when to query other agents, when to keep on querying other agents, and when to settle for an answer. In this way, inter-agent disputes are regulated by the agents themselves, rather than by following an outlined protocol. The paper concludes with a prototype implementation and with a comparison of related work on conversation analysis and computational dialectic.A(colorful and instructive) poster based on a shorter version of this paper was presented at AAMAS'05 . The poster itself can be viewed at http://www.cs.uu.nl/~gv/abstracts/liberal_protocol_poster.pdf. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to modelling embedded agent dialogues. It proposes a specific structure for the supporting information accompanying the arguments that agents exchange during a dialogue, it defines formally how this information relates to the agent theory, and assigns to it semantics that is associated to each of the atomic dialogue types of the Walton-Krabbe typology. This allows the formal definition of necessary and sufficient initiation and acceptance conditions of licit dialectical shifts that are necessary for the modelling of embedded agent dialogues. [ABSTRACT FROM AUTHOR]

Much work in the area of argumentation-based dialogues between agents has been based on the influential taxonomy of dialogue types developed by Walton and Krabbe. In this paper we re-examine the Walton and Krabbe framework, concentrating on the preconditions for different types of dialogue and analyzing them in a systematic way. Doing so identifies a number of new kinds of dialogue missing from the framework. We discuss some of the more interesting of these and develop protocols for them. [ABSTRACT FROM AUTHOR]

One form of argument-based negotiation is when agents argue about why an offer was rejected. If an agent can state a reason for a rejection of an offer, the negotiation process may become more efficient since the other agent can take this reason into account when making new offers. Also, if a reason for rejection can be disputed, the negotiation process may be of higher quality since flawed reasons may be revised as a result. This paper presents a formal protocol for negotiation in which reasons can be asked and given for rejections and in which agents can try to persuade each other that a reason is or is not acceptable. The protocol is modelled as a persuasion dialogue game embedded in a negotiation protocol. It has a social semantics since the protocol does not refer to the internal state of negotiating agents. [ABSTRACT FROM AUTHOR]

Recent years have seen an increasing interest of multiagent system research in employing the theory of argumentation for the development of communication protocols. While significant progress has been made in formalising argument-based communication, (possibly adaptive) agent-level argumentation strategies as a practical integration of rational agent reasoning and inter-agent argumentation dialogues have received fairly little attention. In this paper we propose the use of the InFFrA framework in argument-based negotiation. This framework allows for a strategic and adaptive communication to achieve private goals within the limits of bounded rationality in open argumentation communities. The feasibility of the approach is illustrated in an agent-based web linkage scenario, showing that its performance is comparable to that of simple proposal-based negotiation while accommodating much stricter constraints regarding "what can be said" like those used in argumentation. [ABSTRACT FROM AUTHOR]

Argumentation-based negotiation (ABN) provides agents with an effective means to resolve conflicts within a multi-agent society. However, to engage in such argumentative encounters the agents require the ability to generate arguments, which, in turn, demands four fundamental capabilities: a schema to reason in a social context, a mechanism to identify a suitable set of arguments, a language and a protocol to exchange these arguments, and a decision making functionality to generate such dialogues. This paper focuses on the first two issues and formulates models to capture them. Specifically, we propose a coherent schema, based on social commitments, to capture social influences emanating from the roles and relationships of a multi-agent society. After explaining how agents can use this schema to reason within a society, we then use it to identify two major ways of exploiting social influence within ABN to resolve conflicts. The first of these allows agents to argue about the validity of each other's social reasoning, whereas the second enables agents to exploit social influences by incorporating them as parameters within their negotiation. For each of these, we use our schema to systematically capture a comprehensive set of social arguments that can be used within a multi-agent society. Keywords: Argumentation-based Negotiation, Conflict Resolution. [ABSTRACT FROM AUTHOR]

Argumentation plays a key role in finding a compromise during a negotiation dialogue. It may lead an agent to change its goals/ preferences and force it to respond in a particular way. Two types of arguments are mainly used for that purpose: threats and rewards. For example, if an agent receives a threat, this agent may accept the offer even if it is not fully "acceptable" for it (because otherwise really important goals would be threatened). The contribution of this paper is twofold. On the one hand, a logical setting that handles these two types of arguments is provided. More precisely, logical definitions of threats and rewards are proposed together with their weighting systems. These definitions take into account that negotiation dialogues involve not only agents' beliefs (of various strengths), but also their goals (having maybe different priorities), as well as the beliefs about the goals of other agents. On the other hand, a "simple" protocol for handling such arguments in a negotiation dialogue is given. This protocol shows when such arguments can be presented, how they are handled, and how they lead agents to change their goals and behaviors. Keywords: Argumentation, Negotiation. [ABSTRACT FROM AUTHOR]

Systems of argumentation or 'computational dialectic' are emerging as a powerful means of structuring inter-agent communication in multi-agent systems. Individual systems of computational dialectic have been suggested and implemented to tackle specific problems but no comprehensive and comparative assessment has been made of such systems. This paper introduces ScenarioGC0, a framework for the implementation and testing of a wide range of computational dialectic systems. ScenarioGC0 has a range of benefits for both theoretical and practical work in computational dialectics, including: a means to test arbitrary dialectic systems using a unified knowledge base; a means to determine standard metrics by which dialectic systems can be measured and compared; enabling a body of example dialogue to be assembled for each dialectic system to demonstrate their qualities. [ABSTRACT FROM AUTHOR]

In this paper we describe a framework in which the grounds for one argument's defeat of another is itself subject to argumentation. Hence, given two conflicting arguments, each of which defeat the other, one can then determine the preferred defeat and hence the preferred argument. We then apply this nested argumentation to selection of an agent's preferred ‘instrumental' arguments, where each such argument represents a plan of actions for realising an agent's goals. [ABSTRACT FROM AUTHOR]

Argumentation has received steadily increasing attention in the multi-agent systems community over the past decade, with particular interest in the use of argument models from the informal logic community. The formalisation of such argument systems is a necessary step if they are to be successfully deployed, and their properties rigorously understood. However, there is as yet no widely accepted approach to the formalisation of argument systems. In this paper, we take as our starting point the view that arguments and dialogues are inherently meta-logical, and that any proper formalisation of argument must embrace this aspect of their nature. For example, a statement that serves as a justification of an argument is is statement about an argument: the argument for which the justification serves must itself be referred to in the justification. From this starting position, we develop a formalisation of arguments using a hierarchical first-order meta-logic, in which statements in successively higher tiers of the argumentation hierarchy refer to statements further down the hierarchy. This enables us to give a clean formal separation between object-level statements, arguments made about these object level statements, and statements about arguments. [ABSTRACT FROM AUTHOR]

In this paper we introduce a logic of abstract argumentation capturing Dung's theory of abstract argumentation, based on connectives for attack and defend. We extend it to a modal logic of abstract argumentation to generalize Dung's theory and define variants of it. Moreover, we use the logic to relate Dung's theory of abstract argumentation to more traditional conditional and comparative formalisms, and we illustrate how to reason about arguments in meta-argumentation. [ABSTRACT FROM AUTHOR]

The pragma-dialectical approach to argumentation aims to provide a sound integration of both dialectics — the study of critical exchanges — and pragmatics — the study of language use in actual communication. Pragma dialectics thus combines a dialectical view of argumentative reasonableness with a pragmatic view of the verbal moves made in argumentative discourse. This paper provides an overview of the current state of the pragma-dialectical approach, insofar as this can be done adequately in a single paper, and provides many pointers to the full range of work in this area. [ABSTRACT FROM AUTHOR]