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The SAMBA (Systems for AMBient intelligence enabled by Agents) architecture reported here is a conceptual service-oriented architecture supporting the interaction and interoperability of systems, applications and actors by the notion of an "Ambient Intelligence Element Society". The objective is to provide an ecosystem infrastructure supporting the interaction and interoperability of various elements by encapsulating and representing them through agents acting as members of an Ambient Intelligence Elements Society, and by using executable models at run-time in support of interoperability. [ABSTRACT FROM AUTHOR]

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]

When is it okay to lie? And what constitutes a lie, anyway? This paper examines the notion of lying in agent-based systems, focusing on dialogues and situations where it is acceptable for agents to utter locutions that contradict their beliefs. We examine situations in human and animal behavior where lying — acting or making statements that contradict one's set of beliefs — is considered to be socially acceptable or even necessary for survival. [ABSTRACT FROM AUTHOR]

Argumentation-based negotiation (ABN) is an effective means of resolving conflicts in a multi-agent society. However, it consumes both time and computational resources for agents to generate, select and evaluate arguments. Furthermore, in many cases, argumentation is not the only means of resolving conflicts. Thus, some could be avoided either by finding an alternative means (evading the conflict) or by modifying the intended course of action (re-planning). Therefore, it would be advantageous for agents to identify those situations and weigh the costs and the benefits of arguing before using it to resolve conflicts. To this end, we present a preliminary empirical analysis to evaluate the performance of a simple ABN system, with respect to other non-arguing approaches, in a particular task allocation scenario. In our experiments, we simulate a multi-agent community and allow the agents to use a combination of ABN, evasion and re-planning techniques to overcome conflicts that arise within the community. Analysing the observed results, we show that, in our domain, ABN presents an effective means of resolving conflicts when the resources are constrained. However, we also show it is a more costly and less effective means, compared to evasion and re-planning methods, when resources are more abundant. Keywords: Argumentation-based Negotiation, Conflict Resolution. [ABSTRACT FROM AUTHOR]

Negotiation can be conceived as the exchange of messages among self-interested agents in order to settle on an agreement over a given issue. They decide which messages to send according to their preferences and their evolving beliefs. Agents able to handle this dynamics of messages and beliefs can be represented by means of Defeasible Logic Programming augmented with utility functions. This approach to argumentation has the advantage of providing a useful platform for the representation of beliefs and the generation of messages. The interactive nature of negotiations requires an updating mechanism to be applied over the knowledge bases of the agents. The features of this mechanism are described by a protocol of a negotiation. Although there are many possible protocols, we concentrate on one that ensures the existence of an agreement in negotiations. The formalism of DeLP provides a very natural approach to the characterization of such a protocol. [ABSTRACT FROM AUTHOR]

Negotiation is one of the most fundamental and effective mechanism for resolving conflicts between self-interested agents and producing mutually acceptable compromises. Most existing research in negotiation presumes a fixed negotiation context which cannot be changed during the process of negotiation and that the agents have complete and correct knowledge about all aspects of the issues being negotiated. In practice, the issues being negotiated may change and the agents may have incorrect beliefs of relevant issues updated during the negotiation process. Argumentation-based negotiation approaches have therefore been proposed to capture such realistic negotiation contexts. Here we present a novel Bayesian network based argumentation and decision making framework that allows agents to utilize models of the other agents. The agents will generate effective arguments to influence the other agent's belief and produce more profit. [ABSTRACT FROM AUTHOR]

The notion of agent's goals is crucial in negotiation dialogues. In fact, during a negotiation, each agent tries to make and to accept the offers which satisfy its own goals. Works on negotiation suppose that an agent has a set of fixed goals to pursue. However, it is not shown how these goals are computed and chosen by the agent. Moreover, these works handle one kind of goals: the ones that an agent wants to achieve. Recent studies on psychology claim that goals are bipolar and there are at least two kinds of goals: the positive goals representing what the agent wants to achieve and the negative goals representing what the agent rejects. In this paper, we present an argumentation-based framework which generates the goals of an agent. The framework returns three categories of goals: the positive goals, the negative ones and finally the goals in abeyance. Keywords: Negotiation, Argumentation. [ABSTRACT FROM AUTHOR]

Argumentation-based techniques are being increasingly used to construct frameworks for flexible negotiation among computational agents. Despite the advancements made to date, the relationship between argument-based negotiation and bargaining frameworks has been rather informal. This paper presents a preliminary investigation into understanding this relationship. To this end, we present a set of negotiation concepts through which we analyse both bargaining and argumentation-based methods. We demonstrate that if agents have false beliefs, then they may make decisions during negotiation that lead them to suboptimal deals. We then describe different ways in which argument-based communication can cause changes in an agent's beliefs and, consequently, its preferences over contracts. This enables us to demonstrate how the argumentation-based approach can improve both the likelihood and quality of deals. [ABSTRACT FROM AUTHOR]

We present a denotational semantics for agent deliberation dialogues, i.e., dialogues over proposed actions, conducted under a broad class of interaction protocols. The semantics uses category-theoretic entities to represent deals proposed by agents and the preferences they articulate between these. The semantics is constructed jointly and incrementally by the participating agents in the course of the dialogue, and evolves with the dialogue. We consider properties of the semantics relating to deals and dialogue termination. [ABSTRACT FROM AUTHOR]

We present the syntax and semantics for a multi-agent dialogue game protocol which permits argument over proposals for action. The protocol, called the PARMA Protocol, embodies an earlier theory by the authors of persuasion over action which enables participants to rationally propose, attack, and defend, an action or course of actions (or inaction). We present an outline of both an axiomatic and a denotational semantics, and discuss an implementation of the protocol for two human agents. [ABSTRACT FROM AUTHOR]

In this paper we propose a new persuasion dialogue game for agent communication. We show how this dialogue game is modeled by a framework based on social commitments and arguments. Called Commitment and Argument Network (CAN), this framework allows us to model communication dynamics in terms of actions that agents apply to commitments and in terms of argumentation relations. This dialogue game is specified by indicating its entry conditions, its dynamics and its exit conditions. In order to solve the problem of the acceptance of arguments, the protocol integrates the concept of agents' trustworthiness in its specification. The paper proposes a set of algorithms for the implementation of the persuasion protocol and discusses their termination, complexity and correctness. [ABSTRACT FROM AUTHOR]

This paper establishes an explicit connection between formal argumentation and Bayesian inference by introducing a notion of argument and a notion of defeat among arguments in Bayesian networks. First, the two approaches are compared and it is argued that argumentation in Bayesian belief networks is a typical multi-agent affair. Since in theories of formal argumentation the so-called admissibility semantics is an important criterion of argument validity, this paper finally proposes an algorithm to decide efficiently whether a particular node is supported by an admissible argument. The proposed algorithm is then slightly extended to an algorithm that returns the top-k of strongest admissible arguments at each node. This extension is particularly interesting from a Bayesian inference point of view, because it offers a computationally tractable alternative to the NPPP-complete decision problem k-MPE (finding the top-k most probable explanations in a Bayesian network). [ABSTRACT FROM AUTHOR]