Nir Oren

JAIR Journal 2026 Journal Article

Bases for Weighted Gradual Semantics and Inverse Problems in Argumentation Theory

• Assaf Libman
• Nir Oren
• Bruno Yun

Weighted gradual semantics provide an acceptability degree to each argument representing its final strength, computed based on factors including the argument's background evidence, and taking into account interactions between the argument and others. We introduce five important problems linking gradual semantics and acceptability degrees. First, we re-examine the inverse problem, seeking to identify each argument's initial weights within the argumentation framework which lead to a specific final acceptability degree. Second, we ask whether the function mapping between argument weights and acceptability degrees is one-to-one. Third, we ask if this mapping is a homeomorphism so that small perturbations in weights lead to small perturbation in acceptability degrees and vice versa. Fourth, we ask whether argument weights can be found when preferences, rather than acceptability degrees for arguments are considered. Last, we consider the geometry of the space of valid acceptability degrees, asking whether ``"gaps" exist in this space. While different gradual semantics have been proposed in the literature, in this paper, and building on the geometry of the acceptability degree space, we identify a large family of weighted gradual semantics which contains many of the existing well-known semantics while maintaining desirable properties such as convergence to a unique fixed point and solving all five aforementioned problems.

AAMAS Conference 2025 Conference Paper

Generalised BDI Planning

• Felipe Meneguzzi
• Ramon Fraga Pereira
• Nir Oren

Agent interpreters based on the Beliefs, Desires, and Intentions (BDI) model traditionally perform means-ends reasoning using plan libraries composed of reactive planning rules. However, the design of such rules often imposes a heavy knowledge engineering burden on a designer, and trades off flexibility for runtime efficiency. This use of planning rules originates from the limitations of planning technology at the time of the first BDI implementations. While these limitations have gradually been overcome by the integration of various types of planning into existing BDI theories, the corresponding interpreters remain fundamentally plan-library based. In this paper, we develop a novel BDI agent architecture driven by generalised planning as means-ends reasoning, in a radical departure from existing architectures. This architecture has two key properties. First, it more closely resembles the foundations of BDI logic and reasoning. Second, it offers substantial gains in efficiency in comparison with an architecture driven by classical planning.

AAAI Conference 2025 Conference Paper

Responsibility-aware Strategic Reasoning in Probabilistic Multi-Agent Systems

• Chunyan Mu
• Muhammad Najib
• Nir Oren

Responsibility plays a key role in the development and deployment of trustworthy autonomous systems. In this paper, we focus on the problem of strategic reasoning in probabilistic multi-agent systems with responsibility-aware agents. We introduce the logic PATL+R, a variant of Probabilistic Alternating-time Temporal Logic. The novelty of PATL+R lies in its incorporation of modalities for causal responsibility, providing a framework for responsibility-aware multi-agent strategic reasoning. We present an approach to synthesise joint strategies that satisfy an outcome specified in PATL+R, while optimising the share of expected causal responsibility and reward. This provides a notion of balanced distribution of responsibility and reward gain among agents. To this end, we utilise the Nash equilibrium as the solution concept for our strategic reasoning problem and demonstrate how to compute responsibility-aware Nash equilibrium strategies via a reduction to parametric model checking of concurrent stochastic multi-player games.

ECAI Conference 2023 Conference Paper

Generosity and the Emergence of Forgiveness in the Donation Game

• Nathan Griffiths
• Nir Oren

Research has shown that cooperative action struggles to emerge in the noisy variant of the donation game, a simple model of noisy multi-agent systems where indirect reciprocity is required to maximise utility. Such noise can arise when agents may have an incorrect view of the reputation of their interaction partners, or when the actions themselves may fail. Concepts such as generosity, as well as the use of higher-order norms, have been investigated as mechanisms to facilitate cooperation in such environments, but often are not effective or require additional assumptions or infrastructure in the system to operate. In this paper, we demonstrate both analytically and empirically that a simple form of generosity when combined with fine grained reputation can help cooperation emerge. We also show that the use of individual forgiveness strategies rather than the presence of global generosity can support cooperation in such environments.

JAAMAS Journal 2022 Journal Article

Explaining BDI agent behaviour through dialogue

• Louise A. Dennis
• Nir Oren

Abstract BDI agents act in response to external inputs and their internal plan library. Understanding the root cause of BDI agent action is often difficult, and in this paper we present a dialogue based approach for explaining the behaviour of a BDI agent. We consider two dialogue participants who may have different views regarding the beliefs, plans and external events which drove agent action (encoded via traces). These participants make utterances which incrementally reveal their traces to each other, allowing them to identify divergences in the traces, or to conclude that their traces agree. In practice, we envision a human taking on the role of a dialogue participant, with the BDI agent itself acting as the other participant. The dialogue then facilitates explanation, understanding and debugging of BDI agent behaviour. After presenting our formalism and its properties, we describe our implementation of the system and provide an example of its use in a simple scenario.

IJCAI Conference 2022 Conference Paper

Inverse Problems for Gradual Semantics

• Nir Oren
• Bruno Yun
• Srdjan Vesic
• Murilo Baptista

Gradual semantics with abstract argumentation provide each argument with a score reflecting its acceptability. Many different gradual semantics have been proposed in the literature, each following different principles and producing different argument rankings. A sub-class of such semantics, the so-called weighted semantics, takes, in addition to the graph structure, an initial set of weights over the arguments as input, with these weights affecting the resultant argument ranking. In this work, we consider the inverse problem over such weighted semantics. That is, given an argumentation framework and a desired argument ranking, we ask whether there exist initial weights such that a particular semantics produces the given ranking. The contribution of this paper are: (1) an algorithm to answer this problem, (2) a characterisation of the properties that a gradual semantics must satisfy for the algorithm to operate, and (3) an empirical evaluation of the proposed algorithm.

AAMAS Conference 2021 Conference Paper

Explaining BDI Agent Behaviour through Dialogue

• Louise A. Dennis
• Nir Oren

BDI agents act in response to external inputs and their internal plan library. Understanding the root cause of BDI agent action is often difficult, and in this paper we present a dialogue based approach for explaining the behaviour of a BDI agent. We consider two dialogue participants who may have different views regarding the beliefs, plans and external events which drove agent action (encoded via traces). These participants make utterances which incrementally reveal their traces to each other, allowing them to identify divergences in the traces, or to conclude that their traces agree. In practice, we envision a human taking on the role of a dialogue participant, with the BDI agent itself acting as the other participant. The dialogue then facilitates explanation, understanding and debugging of BDI agent behaviour. After presenting our formalism and its properties, we describe our implementation of the system and provide an example of its use in a simple scenario.

ECAI Conference 2020 Conference Paper

From Eigentrust to a Trust-Measuring Algorithm in the Max-Plus Algebra

• Juan Afanador
• Nir Oren
• Murilo S. Baptista
• Maria Araujo

Eigentrust is a simple and popular method for trust computation, which uses both direct and indirect information about individual performance to provide a global trust rating. This final trust value is based on eigenvectors computed through the Power Method. However, under certain network topologies, the Power Method cannot be used to identify appropriate eigenvectors. After characterising these cases, we overcome Eigentrust’s limitations by extending the algorithm’s core ideas into the Max-Plus Algebra. An empirical evaluation of our new approach demonstrates its superiority to Eigentrust.

AIJ Journal 2020 Journal Article

Landmark-based approaches for goal recognition as planning

• Ramon Fraga Pereira
• Nir Oren
• Felipe Meneguzzi

Recognizing goals and plans from complete or partial observations can be efficiently achieved through automated planning techniques. In many applications, it is important to recognize goals and plans not only accurately, but also quickly. To address this challenge, we develop novel goal recognition approaches based on planning techniques that rely on planning landmarks. In automated planning, landmarks are properties (or actions) that cannot be avoided to achieve a goal. We show the applicability of a number of planning techniques with an emphasis on landmarks for goal recognition tasks in two settings: (1) we use the concept of landmarks to develop goal recognition heuristics; and (2) we develop a landmark-based filtering method to refine existing planning-based goal and plan recognition approaches. These recognition approaches are empirically evaluated in experiments over several classical planning domains. We show that our goal recognition approaches yield not only accuracy comparable to (and often higher than) other state-of-the-art techniques, but also result in substantially faster recognition time over existing techniques.

TIST Journal 2020 Journal Article

Using Sub-Optimal Plan Detection to Identify Commitment Abandonment in Discrete Environments

• Ramon Fraga Pereira
• Nir Oren
• Felipe Meneguzzi

Assessing whether an agent has abandoned a goal or is actively pursuing it is important when multiple agents are trying to achieve joint goals, or when agents commit to achieving goals for each other. Making such a determination for a single goal by observing only plan traces is not trivial, as agents often deviate from optimal plans for various reasons, including the pursuit of multiple goals or the inability to act optimally. In this article, we develop an approach based on domain independent heuristics from automated planning, landmarks, and fact partitions to identify sub-optimal action steps—with respect to a plan—within a fully observable plan execution trace. Such capability is very important in domains where multiple agents cooperate and delegate tasks among themselves, such as through social commitments, and need to ensure that a delegating agent can infer whether or not another agent is actually progressing towards a delegated task. We demonstrate how a creditor can use our technique to determine—by observing a trace—whether a debtor is honouring a commitment. We empirically show, for a number of representative domains, that our approach infers sub-optimal action steps with very high accuracy and detects commitment abandonment in nearly all cases.

TAAS Journal 2019 Journal Article

Argumentation-Based Reasoning about Plans, Maintenance Goals, and Norms

• Zohreh Shams
• Marina De Vos
• Nir Oren
• Julian Padget

In a normative environment, an agent’s actions are directed not only by its goals but also by the norms activated by its actions and those of other actors. The potential for conflict between agent goals and norms makes decision making challenging, in that it requires looking ahead to consider the longer-term consequences of which goal to satisfy or which norm to comply with in face of conflict. We therefore seek to determine the actions an agent should select at each point in time, taking account of its temporal goals, norms, and their conflicts. We propose a solution in which a normative planning problem is the basis for practical reasoning based on argumentation. Various types of conflict within goals, within norms, and between goals and norms are identified based on temporal properties of these entities. The properties of the best plan(s) with respect to goal achievement and norm compliance are mapped to arguments, followed by mapping their conflicts to attack between arguments, all of which are used to identify why a plan is justified.

AAMAS Conference 2017 Conference Paper

Detecting Commitment Abandonment by Monitoring Sub-Optimal Steps during Plan Execution

• Ramon Fraga Pereira
• Nir Oren
• Felipe Meneguzzi

AAAI Conference 2017 Conference Paper

Landmark-Based Heuristics for Goal Recognition

• Ramon Pereira
• Nir Oren
• Felipe Meneguzzi

Automated planning can be used to efficiently recognize goals and plans from partial or full observed action sequences. In this paper, we propose goal recognition heuristics that rely on information from planning landmarks — facts or actions that must occur if a plan is to achieve a goal when starting from some initial state. We develop two such heuristics: the first estimates goal completion by considering the ratio between achieved and extracted landmarks of a candidate goal, while the second takes into account how unique each landmark is among landmarks for all candidate goals. We empirically evaluate these heuristics over both standard goal/plan recognition problems, and a set of very large problems. We show that our heuristics can recognize goals more accurately, and run orders of magnitude faster, than the current state-of-the-art.

ECAI Conference 2016 Conference Paper

A Bayesian Approach to Norm Identification

• Stephen Cranefield
• Felipe Meneguzzi
• Nir Oren
• Bastin Tony Roy Savarimuthu

When entering a system, an agent should be aware of the obligations and prohibitions (collectively norms) that affect it. Existing solutions to this norm identification problem make use of observations of either norm compliant, or norm violating, behaviour. Thus, they assume an extreme situation where norms are typically violated, or complied with. In this paper we propose a Bayesian approach to norm identification which operates by learning from both norm compliant and norm violating behaviour. We evaluate our approach's effectiveness empirically and compare its accuracy to existing approaches. By utilising both types of behaviour, we not only overcome a major limitation of such approaches, but also obtain improved performance over the state of the art, allowing norms to be learned with fewer observations.

JELIA Conference 2016 Conference Paper

A Two-Phase Dialogue Game for Skeptical Preferred Semantics

• Zohreh Shams
• Nir Oren

Abstract In this paper we propose a labelling based dialogue game for determining whether a single argument within a Dung argumentation framework is skeptically preferred. Our game consists of two phases, and determines the membership of a single argument within the extension, assuming optimal play by dialogue participants. In the first phase, one player attempts to advance arguments to construct an extension not containing the argument under consideration, while the second phase verifies that the extension is indeed a preferred one. Correctness within this basic game requires perfect play by both players, and we therefore also introduce an overarching game to overcome this limitation.

AAAI Conference 2016 Conference Paper

Markov Argumentation Random Fields

• Yuqing Tang
• Nir Oren
• Katia Sycara

IJCAI Conference 2016 Conference Paper

Normative Practical Reasoning via Argumentation and Dialogue

• Zohreh Shams
• Marina De Vos
• Nir Oren
• Julian Padget

In a normative environment an agent's actions are not only directed by its goals but also by norms. Here, potential conflicts among the agent's goals and norms makes decision-making challenging. We therefore seek to answer the following questions: (i) how should an agent act in a normative environment? and (ii) how can the agent explain why it acted in a certain way? We propose a solution in which a normative planning problem serves as the basis for a practical reasoning approach based on argumentation. The properties of the best plan(s) w. r. t. goal achievement and norm compliance are mapped to arguments that are used to explain why a plan is justified, using a dialogue game.

EAAI Journal 2015 Journal Article

BDI reasoning with normative considerations

• Felipe Meneguzzi
• Odinaldo Rodrigues
• Nir Oren
• Wamberto W. Vasconcelos
• Michael Luck

Systems of autonomous and self-interested agents interacting to achieve individual and collective goals may exhibit undesirable or unexpected behaviour if left unconstrained. Norms have been widely proposed as a means of defining and enforcing societal constraints by using the deontic concepts of obligations, permissions and prohibitions to describe what must, may and should not be done, respectively. However, recent efforts to provide norm-enabled agent architectures that guide plan choices suffer from interfering with an agent׳s reasoning process, and thus limit the agent׳s autonomy more than is required by the norms alone. In this paper we describe an extension of the Beliefs–Desires–Intentions (BDI) architecture that enables normative reasoning used to help agents choose and customise plans taking norms into account. The paper makes three significant contributions: we provide a formal framework to represent norms compactly and to manage them; we present a formal characterisation of the normative positions induced by norms of an agent׳s execution within a given time period; and finally, we put forth a mechanism for plan selection and ranking taking into consideration a set of normative restrictions.

AILAW Journal 2015 Journal Article

Monitoring compliance with E-contracts and norms

• Sanjay Modgil
• Nir Oren
• Noura Faci
• Felipe Meneguzzi
• Simon Miles
• Michael Luck

Abstract The behaviour of autonomous agents may deviate from that deemed to be for the good of the societal systems of which they are a part. Norms have therefore been proposed as a means to regulate agent behaviours in open and dynamic systems, where these norms specify the obliged, permitted and prohibited behaviours of agents. Regulation can effectively be achieved through use of enforcement mechanisms that result in a net loss of utility for an agent in cases where the agent’s behaviour fails to comply with the norms. Recognition of compliance is thus crucial for achieving regulation. In this paper, we propose a general framework for observation of agents’ behaviour, and recognition of this behaviour as constituting, or counting as, compliance or violation. The framework deploys monitors that receive inputs from trusted observers, and processes these inputs together with transition network representations of individual norms. In this way, monitors determine the fulfillment or violation status of norms. The paper also describes a proof of concept implementation of the framework, and its deployment in electronic contracting environments.

ECAI Conference 2014 Conference Paper

Dynamic Taxi Pricing

• Cheng Zeng
• Nir Oren

Taxi journeys are usually priced according to the distance covered and time taken for the trip. Such a fixed cost strategy is simple to understand, but does not take into account the likelihood that a taxi can pick up additional passengers at the original passenger's destination. In this paper we investigate dynamic taxi pricing strategies. By using domain knowledge, such strategies discount trips to locations containing many potential passengers, and increase fares to those areas with few potential passengers. Identifying a closed form optimal dynamic pricing strategy is difficult, and by representing the domain as an MDP, we can identify an optimal strategy for specific domains. We empirically compare such dynamic pricing strategies with fixed cost strategies, and suggest future extensions to this work.

ECAI Conference 2014 Conference Paper

Formal Arguments, Preferences, and Natural Language Interfaces to Humans: an Empirical Evaluation

• Federico Cerutti 0001
• Nava Tintarev
• Nir Oren

It has been claimed that computational models of argumentation provide support for complex decision making activities in part due to the close alignment between their semantics and human intuition. In this paper we assess this claim by means of an experiment: people's evaluation of formal arguments - presented in plain English - is compared to the conclusions obtained from argumentation semantics. Our results show a correspondence between the acceptability of arguments by human subjects and the justification status prescribed by the formal theory in the majority of the cases. However, post-hoc analyses show that there are some significant deviations, which appear to arise from implicit knowledge regarding the domains in which evaluation took place. We argue that in order to create argumentation systems, designers must take implicit domain specific knowledge into account.

IS Journal 2014 Journal Article

Supporting Trust Assessment and Decision Making in Coalitions

• Chris Burnett
• Timothy J. Norman
• Katia Sycara
• Nir Oren

Modern multiorganizational coalitions can bring diverse sets of capabilities, assets, and information sources to bear on complex and dynamic operations. However, successfully completing these operations places demands on the trust between coalition partners. When it's necessary to rely on other partners, decision makers must be able to make rapid and effective trust assessments and decisions. Here, the authors focus on coalition information acquisition and discuss mechanisms for assessing trust and arriving at decisions about how to act when trust can be supplemented by controls. They also discuss future directions for these systems and highlight outstanding challenges.

IJCAI Conference 2013 Conference Paper

Opponent Models with Uncertainty for Strategic Argumentation

• Tjitze Rienstra
• Matthias Thimm
• Nir Oren

This paper deals with the issue of strategic argumentation in the setting of Dung-style abstract argumentation theory. Such reasoning takes place through the use of opponent models—recursive representations of an agent’s knowledge and beliefs regarding the opponent’s knowledge. Using such models, we present three approaches to reasoning. The first directly utilises the opponent model to identify the best move to advance in a dialogue. The second extends our basic approach through the use of quantitative uncertainty over the opponent’s model. The final extension introduces virtual arguments into the opponent’s reasoning process. Such arguments are unknown to the agent, but presumed to exist and interact with known arguments. They are therefore used to add a primitive notion of risk to the agent’s reasoning. We have implemented our models and we have performed an empirical analysis that shows that this added expressivity improves the performance of an agent in a dialogue.

EAAI Journal 2012 Journal Article

Applying electronic contracting to the aerospace aftercare domain

• Felipe Meneguzzi
• Sanjay Modgil
• Nir Oren
• Simon Miles
• Michael Luck
• Noura Faci

The contract project was a European Commission project whose aim was to develop frameworks, components and tools to model, build, verify and monitor distributed electronic business systems based on electronic contracts. In this context, an electronic contract provides a specification of the expected behaviours of individual services, with the assumption that these services are often enacted by autonomous agents. Using the theoretical tools created by the project, in this paper we describe the complete life cycle of instantiating an electronic contracting system using the contract framework within the aerospace aftercare domain. Thus, we use a natural language description of parts of the types of contracts used in this domain to generate individual norms amenable to a computational representation, and how these norms are used to generate a concrete contract monitor. Moreover, we describe a concrete implementation of contract agents in the AgentSpeak(L) language and how these agents interact within a concrete instantiation of contract.

AAMAS Conference 2012 Conference Paper

Sub-delegation and Trust

• Chris Burnett
• Nir Oren

Trust mechanisms can allow an agent to identify the most trustworthy entity to which a task should be delegated. Now this entity may further delegate the task, ultimately resulting in a delegation chain representing the sub-delegation process. Such delegation chains present a problem for current trust evaluation mechanisms, as they typically which reward or penalise a single agent rather than sharing responsibility among all members of the delegation chain. As a result, decisions made on such incorrect trust values would not be optimal, leading to degraded system performance. In this paper we investigate the effects of sub-delegation on a probabilistic trust model and propose a model of weighting trust updates based on shared responsibility. We evaluate this model in the context of a simulated multi-agent system and describe how different weighting strategies can affect probabilistic trust updates when sub-delegation is possible.

AAMAS Conference 2010 Conference Paper

A Model of Normative Power

• Nir Oren
• Michael Luck
• Simon Miles

A power describes the ability of an agent to act in some way. Whilethis notion of power is critical in the context of organisational dynamics, and has been studied by others in this light, it must beconstrained so as to be useful in any practical application. In particular, we are concerned with how power may be used by agents togovern the imposition and management of norms, and how agentsmay dynamically assign norms to other agents within a multi-agentsystem. We approach the problem by defining a syntax and semantics for powers governing the creation, deletion, or modification ofnorms within a system, which we refer to as normative powers. Wethen extend this basic model to accommodate more general powers that can modify other powers within the system, and describehow agents playing certain roles are able to apply powers, changingthe system's norms, and also the powers themselves. We examinehow the powers found within a system may change as the statusof norms change, and show how standard norm modification operations - such as the derogation, annulment and modification ofnorms - may be represented within our system.

AAMAS Conference 2010 Conference Paper

A Simulation Approach to Design Contracts that Govern Emergent Multi-Agent Systems

• Ma
• iacute; ra Gatti
• Simon Miles
• Nir Oren
• Michael Luck
• Carlos Lucena

Governing the behavior of autonomous agents in multi-agent systems to reach overall system benefit has long been an active area of research. One approach of recent prevalence is to provide agents with explicit specifications of what they should, should not or may do within the system, i. e. normative statements or norms. In a business setting, these norms exactly mirror the contractual agreements made between business organizations. As such, agent-based normative systems offer the potential for a business to model, understand the consequences of, and then refine contracts to improve the outcomes for that business. However, languages and tools for specifying norms do not by themselves provide understanding of the emergent behavior in a complex domain. In this paper, we combine a simulation technique designed for investigating and tuning emergent behavior in multi-agent systems with an approach to modeling norms of the complexity found in business contracts. We show, using an aerospace case study, that our approach can aid in the refinement of such contracts by exposing the consequences of contract variations.

AAMAS Conference 2010 Conference Paper

Graphically Explaining Norms

• Madalina Croitoru
• Nir Oren
• Simon Miles
• Michael Luck

While much work has focused on the creation of norm aware agents, much less has been concerned with aiding a system's designers inunderstanding the effects of norms on a system. However, sincenorms are generally pre-determined by designers, providing suchsupport can be critical in enabling norm refinement for more effective or efficient system regulation. In this paper, we address just thisproblem by providing explanations as to why some norm is applicable, violated, or in some other state. We make use of conceptualgraph based semantics to provide an easily interpretable graphicalrepresentation of the norms within a system. Such a representationallows for visual explanation of the state of norms, showing forexample why they may have been activated or violated. These explanations then enables easy understanding of the system operationwithout needing to follow the system's underlying logic.

AAMAS Conference 2009 Conference Paper

A Framework for Monitoring Agent-Based Normative Systems

• Sanjay Modgil
• Noura Faci
• Felipe Meneguzzi
• Nir Oren
• Simon Miles
• Michael Luck

The behaviours of autonomous agents may deviate from those deemed to be for the good of the societal systems of which they are a part. Norms have therefore been proposed as a means to regulate agent behaviours in open and dynamic systems, where these norms specify the obliged, permitted and prohibited behaviours of agents. Regulation can effectively be achieved through use of enforcement mechanisms that result in a net loss of utility for an agent in cases where the agent’s behaviour fails to comply with the norms. Recognition of compliance is thus crucial for achieving regulation. In this paper we propose a generic architecture for observation of agent behaviours, and recognition of these behaviours as constituting, or counting as, compliance or violation. The architecture deploys monitors that receive inputs from observers, and processes these inputs together with transition network representations of individual norms. In this way, monitors determine the fulfillment or violation status of norms. The paper also describes a proof of concept implementation and deployment of monitors in electronic contracting environments.

IJCAI Conference 2007 Conference Paper

• Nir Oren
• Timothy. Norman
• Alun Preece

Few existing argumentation frameworks are designed to deal with probabilistic knowledge, and none are designed to represent possibilistic knowledge, making them unsuitable for many real world domains. In this paper we present a subjective logic based framework for argumentation which overcomes this limitation. Reasoning about the state of a literal in this framework can be done in polynomial time. A dialogue game making use of the framework and a utility based heuristic for playing the dialogue game are also presented. We then show how these components can be applied to contract monitoring. The dialogues that emerge bear some similarity to the dialogues that occur when humans argue about contracts, and our approach is highly suited to complex, partially observable domains with fallible sensors where determining environment state cannot be done for free.

AIJ Journal 2007 Journal Article

Subjective logic and arguing with evidence

• Nir Oren
• Timothy J. Norman
• Alun Preece

This paper introduces a subjective logic based argumentation framework primarily targeted at evidential reasoning. The framework explicitly caters for argument schemes, accrual of arguments, and burden of proof; these concepts appear in many types of argument, and are particularly useful in dialogues revolving around evidential reasoning. The concept of a sensor is also useful in this domain, representing a source of evidence, and is incorporated in our framework. We show how the framework copes with a number of problems that existing frameworks have difficulty dealing with, and how it can be situated within a simple dialogue game. Finally, we examine reasoning machinery that enables an agent to decide what argument to advance with the goal of maximising its utility at the end of a dialogue.

ECAI Conference 2006 Conference Paper

Arguing with Confidential Information

• Nir Oren
• Timothy J. Norman
• Alun David Preece

While researchers have looked at many aspects of argumentation, an area often neglected is that of argumentation strategies. That is, given multiple possible arguments that an agent can put forth, which should be selected in what circumstances. In this paper, we propose a heuristic that implements one such strategy. The heuristic assigns a utility cost to revealing information, as well as a utility to winning, drawing and losing an argument. An agent participating in a dialogue then attempts to maximise its utility. We present a formal argumentation framework in which this heuristic may operate, and show how it functions within the framework. Finally, we discuss how this heuristic may be extended in future work, and its relevance to argumentation theory in general.

AAMAS Conference 2006 Conference Paper

CONOISE-G: Agent-based Virtual Organisations

• W. T. Luke Teacy
• Nicholas R. Jennings
• Michael Luck
• Stuart Chalmers
• Nir Oren
• Timothy J. Norman
• Alun Preece
• Peter M. D. Gray