Publications on Agents

Jeff Blee, David Billington, Guido Governatori, and Abdul Sattar.
Levels of modalities for BDI logic. In 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pages 647-650. IEEE Press, 2008, Copyright © 2008 IEEE.
Abstract: The use of rational agents for modelling real world problems has both been heavily investigated and become well accepted, with BDI Logic being a widely used architecture to represent and reason about rational agency. However, in the real world, we often have to deal with different levels of confidence in our beliefs, desires, and intentions. This paper extends our previous framework that integrated qualitative levels into BDI Logic. We describe an expanded set of axioms and properties of the extended logic and also define a detailed non-normal Kripke type semantics.
 
Guido Boella, Guido Governatori, Joris Hulstijn, Régis Riveret, Antonino Rotolo, and Leendert van der Torre.
Time and defeasibility in FIPA ACL semantics. In 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pages 634-637. IEEE Press, 2008, Copyright © 2008 IEEE.
Abstract: Inferences about communicative actions are often conditional, non-monotonic, and involve the issue of time. Most agent communication languages, however, ignore these issues, due to the difficulty to combine them in a single formalism. This paper addresses such issues in defeasible logic, and illustrates how to express a semantics for ACLs in order to make non-monotonic inferences on the basis of communicative actions.
 
Guido Boella, Guido Governatori, Joris Hulstijn, Régis Riveret, Antonino Rotolo and Leendert van der Torre.
FIPA Communicative Acts in Defeasible Logic. In Alankar Karol, Pavlos Peppas and Mary-Anne Williams, editor, Seventh IJCAI International Workshop on Nonmonotonic Reasoning, Action and Change (NRAC'07), Hyderabad, India, 7-8 January, 2007.
Abstract: In agent communication languages, the inferences that can be made on the basis of a communicative action are inherently conditional, and non-monotonic. For example, a proposal only leads to a commitment, on the condition that it is accepted. And in a persuasion dialogue, assertions may later be retracted. In this paper we therefore present a defeasible logic that can be used to express a semantics for agent communication languages, and to efficiently make inferences on the basis of communicative actions. The logic is non-monotonic, allows nested rules and mental attitudes as the content of communicative actions, and has an explicit way of expressing persistence over time. Moreover, it expresses that mental attitudes are publicly attributed to agents playing roles in the dialogue. To illustrate the usefulness of the logic, we reformalize the meta-theory underlying the FIPA semantics for agent communication, focusing on inform and propose. We show how composed speech acts can be formalalized, and extend the semantics with an account of persuasion.
 
Mehdi Dastani, Guido Governatori, Antonio Rotolo, Insu Song and Leendert van der Torre.
Contextual Deliberation of Cognitive Agents in Defeasible Logic. In 6th International Conference on Autonomous Agents and Multi-Agent Systems. ACM Press, New York. Copyright © 2007 ACM.
Abstract: This article extends Defeasible Logic to deal with the contextual deliberation process of cognitive agents. First, we introduce meta-rules to reason with rules. Meta-rules are rules that have as a consequent rules for motivational components, such as obligations, intentions and desires. In other words, they include nested rules. Second, we introduce explicit preferences among rules. They deal with complex structures where nested rules can be involved.
 
Mehdi Dastani, Guido Governatori, Antonino Rotolo and Leendert van der Torre
Preferences of Agents in Defeasible Logic. In S. Zhang and R. Jarvis, editors, Australian Joint Conference on Artificial Intelligence, AI 2005, pages 695-704. LNCS 3809, Springer, Berlin, 2005, Copyright © 2005 Springer.
Abstract: We are interested in programming languages for cognitive agents with preferences. We define rule-based agent theories and inference procedures in defeasible logic, and in this setting we discuss patterns of agent behavior called agent types.
 
Mehdi Dastani, Guido Governatori, Antonino Rotolo and Leendert van der Torre
Programming Cognitive Agents in Defeasible Logic. In G. Sutcliffe and A. Voronkov, editors, Logic Programming and Automated Reasoning. LPAR 2005, pages 621-635. LNCS 3835, Springer, Berlin, 2005, Copyright © 2005 Springer.
Abstract: Defeasible Logic is extended to programming languages for cognitive agents with preferences and actions for planning. We define rule-based agent theories that contain preferences and actions, together with inference procedures. We discuss patterns of agent types in this setting. Finally, we illustrate the language by an example of an agent reasoning about web-services.
 
Mehdi Dastani, Guido Governatori, Antonino Rotolo, Insu Song, and Leendert van der Torre.
Contextual agent deliberation in defeasible logic. In Aditya Ghose and Guido Governatori, editors, 10 Pacific Rim International Workshop on Multi-Agents, LNAI 5044. Springer, 2008 Copyright © 2008 Springer.
Abstract: This article extends Defeasible Logic to deal with the contextual deliberation process of cognitive agents. First, we introduce meta-rules to reason with rules. Meta-rules are rules that have as a consequent rules for motivational components, such as obligations, intentions and desires. In other words, they include nested rules. Second, we introduce explicit preferences among rules. They deal with complex structures where nested rules can be involved.
 
Paolo Di Giusto and Guido Governatori.
Analytic modal revision for multi-agent systems. In Pedro Barahona and José Júlio Alferes, editors, Progress in Artificial Intelligence, volume 1695 of LNAI, pages 282-296, Berlin, 1999. Springer-Verlag, Copyright © 1999 Springer-Verlag.
Abstract:We present two models of hierarchical structured multi-agents, and we describe how to obtain a modal knowledge base from distributed sources. We then propose a computationally oriented revision procedure for modal knowledge bases. This procedure is based on a labelled tableaux calculi supplemented with a formalism to record the dependencies of the formulae. The dependencies are then used to reconstruct the minimal inconsistent sets, and the sub-formulae responsible for the inconsistencies are revised according to well-defined chains of modal functions.
 
Marlon Dumas, Lachlan Aldred, Guido Governatori, and Arthur H.M. ter Hofstede.
Probabilistic automated bidding in multiple auctions. Journal of Electronic Commerce Research, 5, 1, 25-49, 2005. The original pubblication is available at www.springerlink.com
Abstract:This paper presents an approach to develop bidding agents that participate in multiple alternative auctions, with the goal of obtaining an item with a given probability. The approach consists of a prediction method and a planning algorithm. The prediction method exploits the history of past auctions in order to build probability functions capturing the belief that a bid of a given price may win a given auction. The planning algorithm computes a price, such that by sequentially bidding in a subset of the relevant auctions, the agent can obtain the item at that price with the desired probability. The approach addresses the case where the auctions are for substitutive items with different values. Experimental results show that the approach increases the payoff of their users and the welfare of the market.
 
Marlon Dumas, Guido Governatori, Arthur H. M. ter Hofstede, and Phillipa Oaks.
A formal approach to negotiating agents development. Electronic Commerce Research and Applications, 1 no. 2, 193-207, 2002., Copyright © 2002 Elsevier Science B.V..
Abstract:This paper presents a formal and executable approach to capture the behaviour of parties involved in a negotiation. A party is modeled as a negotiating agent composed of a communication module, a control module, a reasoning module, and a knowledge base. The control module is expressed as a statechart, and the reasoning module as a defeasible logic program. A strategy specification therefore consists of a statechart, a set of defeasible rules, and a set of initial facts. Such a specification can be dynamically plugged into an agent shell incorporating a statechart interpreter and a defeasible logic inference engine, in order to yield an agent capable of participating in a given type of negotiations. The choice of statecharts and defeasible logic with respect to other formalisms is justified against a set of desirable criteria, and their suitability is illustrated through concrete examples of bidding and multi-lateral bargaining scenarios.
 
Jenny Eriksson Lundström, Guido Governatori, Subhasis Thakur, and Vineet Padmanabhan.
An asymmetric protocol for argumentation games in defeasible logic. In Aditya Ghose and Guido Governatori, editors, 10 Pacific Rim International Workshop on Multi-Agents, LNAI 5044. Springer, 2008 Copyright © 2008 Springer.
Abstract: Agent interactions where the agents hold conflicting goals could be modelled as adversarial argumentation games. In many real-life situations (e.g., criminal litigation, consumer legislation), due to ethical, moral or other principles governing interaction, the burden of proof, i.e., which party is to lose if the evidence is balanced, is a priori fixed to one of the parties. Analogously, when resolving disputes in a heterogeneous agent-system the unequal importance of different agents for carrying out the overall system goal need to be accounted for. In this paper we present an asymmetric protocol for an adversarial argumentation game in Defeasible Logic, suggesting Defeasible Logic as a general representation formalism for argumentation games modelling agent interactions.
 
Jonathan Gelati, Guido Governatori, Antonino Rotolo, and Giovanni Sartor.
Declarative power, representation, and mandate: A formal anaysis. In Trevor Bench-Capon, Aspassia Daskalopulu, and Radboudb Winkels, editors, Legal Knowledge and Information Systems, number 89 in Frontieres in Artificial Intelligence and Applications, pages 41-52. IOS Press, Amsterdam, 2002.
Abstract:In this paper we provide a formal framework for developing the idea of normative co-ordination. We argue that this idea is based on the assumption that agents can achieve flexible co-ordination by conferring normative positions to other agents. These positions include duties, permissions, and powers. In particular, we introduce the idea of declarative power, which consists in the capacity of the power-holder of creating normative positions, involving other agents, simply by ``proclaiming'' such positions. In addition, we account also for the concepts of representation, consisting in the representative's capacity of acting in the name of his principal, and of mandate, which corresponds the mandatee's duty to act as the mandator has requested. Finally, we show how the above framework can be applied to the contract-net protocol.
 
Jonathan Gelati, Guido Governatori, Antonino Rotolo, and Giovanni Sartor.
Normative autonomy and normative co-ordination: Declarative power, representation, and mandate. Artificial Intelligence and Law, 12 (1-2), 53-81. 2004. Copyright © 2004 Springer. The original publication is available at www.springerlink.com
Abstract:In this paper we provide a formal analysis of the idea of normative co-ordination. We argue that this idea is based on the assumption that agents can achieve flexible co-ordination by conferring normative positions to other agents. These positions include duties, permissions, and powers. In particular, we explain the idea of declarative power, which consists in the capacity of the power-holder of creating normative positions, involving other agents, simply by ``proclaiming'' such positions. In addition, we account also for the concepts of representation, namely the representative's capacity of acting in the name of his principal, and of mandate, which is the mandatee's duty to act as the mandator has requested. Finally, we show how the framework can be applied to represent the contract-net protocol. Some brief remarks on future research and applications conclude this contribution.
 
Guido Governatori, Jonathan Gelati, Antonino Rotolo, and Giovanni Sartor.
Actions, institutions, powers. preliminary notes. In Gabriela Lindemann, Daniel Moldt, Mario Paolucci, and Bin Yu, editors, International Workshop on Regulated Agent-Based Social Systems: Theories and Applications (RASTA'02), volume 318 of Mitteilung, pages 131-147. Fachbereich Informatik, Universität Hamburg.
Abstract:In this paper we analyse some logical notions relevant for representing the dynamics of institutionalised organisations. In particular, some well-known action concepts introduced in the Kanger-Lindahl-Pörn logical theory of agency are discussed and integrated. Secondly, moving from the work of Jones and Sergot, a logical characterisation is provided of the ideas of institutional links, ``counts-as'' connections, and institutional facts. This approach is then enriched by a new modal operator proc, intended to account for the autonomous and decentralised creation of new institutional facts and normative positions within institutions.
 
Guido Governatori and Renato Iannella.
A modelling and reasoning framework for social networks policies. Enterprise Information Systems, 2010 Copyrigth © 2010 Taylor & Francis.
Abstract: Policy languages (such as privacy and rights) have had little impact on the wider community. Now that Social Networks have taken off, the need to revisit Policy languages and realign them towards Social Networks requirements has become more apparent. One such language is explored as to its applicability to the Social Networks masses. We also argue that policy languages alone are not sufficient and thus they should be paired with reasoning mechanisms to provide precise and unambiguous execution models of the policies. To this end we propose a computationally oriented model to represent, reason with and execute policies for Social Networks.
 
Guido Governatori, Alessio Lomuscio, and Marek Sergot.
A tableaux system for deontic interpreted systems. In Tamás D. Gedeon and Lance Chun Che Fung, editors, AI 2003: Advances in Artificial Intelligence, volume 2903 of LNAI, pages 339-351, Springer-Verlag, Berlin, 2003. Copyright © 2003 Springer-Verlag.
Abstract:We develop a labelled tableaux system for the modal logic $KD45^i-j_n$ extended with epistemic notions. This logic characterises a particular type of interpreted systems used to represent and reason about states of correct and incorrect functioning behaviour of the agents in a system, and of the system as a whole. The resulting tableaux system provides a simple decision procedure for the logic. We discuss these issues and we illustrate them with the help of simple examples.
 
Guido Governatori, Mehmet A. Orgun, and Chuchang Liu.
Modal tableaux for verifying stream authentication protocols. Journal of Autonomous Agents and Multi Agent Systems, 19 no. 1: 53-75, 2009, Copyright © 2008 Springer.
Abstract: To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for the resulting fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments.
 
Guido Governatori and Vineet Padmanabhan.
A defeasible logic of policy-based intention. In Tamás D. Gedeon and Lance Chun Che Fung, editors, AI 2003: Advances in Artificial Intelligence, volume 2903 of LNAI, pages 414-426, Springer-Verlag, Berlin, 2003. Copyright © 2003 Springer-Verlag.
Abstract:Most of the theories on formalising intention interpret it as a unary modal operator in Kripkean semantics, which gives it a monotonic look. We argue that policy-based intentions exhibit non-monotonic behaviour which could be captured through a non-monotonic system like defeasible logic. To this end we outline a defeasible logic of intention. The proposed technique alleviates most of the problems related to logical omniscience. The proof theory given shows how our approach helps in the maintenance of intention-consistency in agent systems like BDI.
 
Guido Governatori, Vineet Padmanabhan, and Rotolo. Antonino.
Rule-based agents in temporalised defeasible logic. In Qiang Yang and Geoff Webb, editors, Ninth Pacific Rim International Conference on Artificial Intelligence, LNAI 4099, pages 31-40, Guilin, 7-11 August 2006. Springer, Berlin, 2006. Copyright © 2006 Springer.
Abstract:This paper provides a framework based on temporal defeasible logic to reason about deliberative rule-based cognitive agents. Compared to previous works in this area our framework has the advantage that it can reason about temporal rules. We show that for rule-based cognitive agents deliberation is more than just deriving conclusions in terms of their mental components. Our paper is an extension of \cite{ai05,lpar05} in the area of cognitive agent programming.
 
Guido Governatori, Vineet Padmanabhan, Antonino Rotolo, and Abdul Sattar.
A defeasible logic for modelling policy-based intentions and motivational attitudes. Logic Journal of the IGPL, 17(3), 2009.Copyright © 2009 Oxford University Press.
Abstract: In this paper we show how defeasible logic could formally account for the non-monotonic properties involved in motivational attitudes like intention and obligation. Usually, normal modal operators are used to represent such attitudes wherein classical logical consequence and the rule of necessitation comes into play i.e., $\vdash A / \vdash \Box A$, that is from $\vdash A$ derive $\vdash\Box A$. This means that such formalisms are affected by the Logical Omniscience problem. We show that policy-based intentions exhibit non-monotonic behaviour which could be captured through a non-monotonic system like defeasible logic. To this end we outline a defeasible logic of intention that specifies how modalities can be introduced and manipulated in a non-monotonic setting without giving rise to the problem of logical omniscience. In a similar way we show how to add deontic modalities defeasibly and how to integrate them with other motivational attitudes like beliefs and goals. Finally we show that the basic aspect of the BOID architecture is captured by this extended framework.
 
Guido Governatori, Vineet N. Padmanabhan, and Abdul Sattar.
On fibring semantics for BDI logics. In Sergio Leone and Nicola Greco, editors, JELIA, LNAI, Berlin, 2002. Springer-Verlag, Copyright © 2002 Springer-Verlag.
Abstract:This study examines BDI logics in the context of Gabbay's fibring semantics. We show that dovetailing (a special form of fibring) can be adopted as a semantic methodology to combine BDI logics. We develop a set of interaction axioms that can capture static as well as dynamic aspects of the mental states in BDI systems, using Catach's incestual schema Ga, b, c, d. Further we exemplify the constraints required on fibring function to capture the semantics of interactions among modalities. The advantages of having a fibred approach is discussed in the final section.
 
Guido Governatori and Antonino Rotolo.
A computational framework for non-monotonic agency, institutionalised power and multi-agent systems. In Daniéle Bourcier, editor, Legal Knowledge and Inforamtion Systems, volume 106 of Frontieres in Artificial Intelligence and Applications, pages 151-152, IOS Press, Amsterdam, 2003.
 
Guido Governatori and Antonino Rotolo.
A defeasible logic of institutional agency. In Gerhard Brewka and Pavlos Peppas, editors, NRAC'03, pages 97-104, Acapulco, Mexico, 10-11 August 2003. IJCAI.
Abstract:A non-monotonic logic of institutional agency is defined combining a computationally oriented non-monotonic system (Defeasible Logic) and intensional notions of agency.
 
Guido Governatori and Antonino Rotolo.
Defeasible logic: Agency and obligation. In Alessio Lomuscio and Donald Nute, editors, Deontic Logic in Computer Science, number 3065 in LNAI, pages 114-128, Springer-Verlag, Berlin, 2004. Copyright © 2004 Spinger. The original pubblication is available at www.springerlink.com
Abstract:We propose a computationally oriented non-monotonic multi-modal logic arising from the combination of agency, intention and obligation. We argue about the defeasible nature of these notions and then we show how to represent and reason with them in the setting of defeasible logic.
 
Guido Governatori and Antonino Rotolo.
On the axiomatization of Elgesem's logic of agency. In Mark Reynold and Heinrich Wansing, editors, Advances in Modal Logic 5, Manchester, 8-11 September 2004.
Abstract: In this paper we show that the Hilbert system of agency and ability presented by Dag Elgesem is incomplete with respect to the intended semantics. We argue that completeness result may be easily regained. Finally, we shortly discuss some issues related to the philosophical intuition behind his approach. This is done by examining Elgesem's modal logic of agency and ability using semantics with different flavours.
 
Guido Governatori and Antonino Rotolo.
On the axiomatization of Elgesem's logic of agency and ability. Journal of Philosophical Logic, 34, 4, pp. 403-431. The original publication is available at www.springerlink.com.
Abstract:In this paper we show that the Hilbert system of agency and ability presented by Dag Elgesem is incomplete with respect to the intended semantics. We argue that completeness result may be easily regained. Finally, we shortly discuss some issues related to the philosophical intuition behind his approach. This is done by examining Elgesem's modal logic of agency and ability using semantics with different flavours.
 
Guido Governatori and Antonino Rotolo.
A computational framework for institutional agency. Artificial Intelligence and Law, 16 no. 1 pp. 25-52, 2008., Copyright © 2008 Springer.
Abstract: This paper provides a computational framework, based on Defeasible Logic, to capture some aspects of institutional agency. Our background is Kanger-Lindahl-Pörn account of organised interaction, which describes this interaction within a multi-modal logical setting. This work focuses in particular on the notions of counts-as link and on those of attempt and of personal and direct action to realise states of affairs. We show how standard Defeasible Logic can be extended to represent these concepts: the resulting system preserves some basic properties commonly attributed to them. In addition, the framework enjoys nice computational properties, as it turns out that the extension of any theory can be computed in time linear to the size of the theory itself.
 
Guido Governatori and Antonino Rotolo.
BIO logical agents: Norms, beliefs, intentions in defeasible logic. Journal of Autonomous Agents and Multi Agent Systems, 2008. Copyright © 2008 Springer.
Abstract: In this paper we follow the BOID (Belief, Obligation, Intention, Desire) architecture to describe agents and agent types in Defeasible Logic. We argue, in particular, that the introduction of obligations can provide a new reading of the concepts of intention and intentionality. Then we examine the notion of social agent (i.e., an agent where obligations prevail over intentions) and discuss some computational and philosophical issues related to it. We show that the notion of social agent either requires more complex computations or has some philosophical drawbacks.
 
Guido Governatori and Antonino Rotolo.
How do agents comply with norms?. In Guido Boella, Pablo Noriega, Gabriella Pigozzi, and Harko Verhagen, editors, Normative Multi-Agent Systems, number 09121 in Dagstuhl Seminar Proceedings, Dagstuhl, Germany, 2009. Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik, Germany.
Abstract: The import of the notion of institution in the design of MASs requires to develop formal and efficient methods for modeling the interaction between agents' behaviour and normative systems. This paper discusses how to check whether agents' behaviour is compliant with the rules regulating them. The key point of our approach is that compliance is a relationship between two sets of specifications: the specifications for executing a process and the specifications regulating it. We propose a logic-based formalism for describing both the semantics of normative specifications and the semantics of compliance checking procedures.
 
Guido Governatori and Antonino Rotolo.
How do agents comply with norms?. In IEEE/WIC/ACM International Joint Conferences on Web Intelligence and Intelligent Agent Technologies, 2009. WI-IAT '09. , volume 3, pages 488-491. IEEE, 2009, Copyright © 2009 IEEE.
Abstract: The import of the notion of institution in the design of MASs requires to develop formal and efficient methods for modeling the interaction between agents' behaviour and normative systems. This paper discusses how to check whether agents' behaviour complies with the rules regulating them. The key point of our approach is that compliance is a relationship between two sets of specifications: the specifications for executing a process and the specifications regulating it. We propose a formalism for describing both the semantics of normative specifications and the semantics of compliance checking procedures.
 
Guido Governatori and Rotolo Antonino.
Justice delayed is justice denied: Logics for a temporal account of reparations and legal compliance. In João Leite, Paolo Torroni, Thomas Ågotnes, Guido Boella, and Leon van der Torre, editors, CLIMA XII, 12th International Workshop on Computational Logic and Multi-Agent Sytems, number LNCS. Springer, 2011, Copyrigth © 2011 Springer.
Abstract: In this paper we extend the logic of violation proposed by Governatori and Rotolo with time, more precisely, we temporalise that logic. The resulting system allows us to capture many subtleties of the concept of legal compliance. In particular, the formal characterisation of compliance can handle different types of legal obligation and different temporal constraints over them. The logic is also able to represent, and reason about, chains of reparative obligations, since in many cases the fulfillment of these types of obligation still amount to legally acceptable situations.
 
Guido Governatori, Antonino Rotolo and Vineet Padmanabhan.
The Cost of Social Agents. In 5th International Conference on Autonomous Agents and Multi-Agent Systems (AAMAS06), ACM Press, 2006. Copyright © 2006 ACM.
Abstract: In this paper we follow the BOID (Belief, Obligation, Intention, Desire) architecture to describe agents and agent types in Defeasible Logic. We argue that the introduction of obligations can provide a new reading of the concepts of intention and intentionality. Then we examine the notion of social agent (i.e., an agent where obligations prevail over intentions) and discuss some computational and philosophical issues related to it. We show that the notion of social agent either requires more complex computations or has some philosophical drawbacks.
 
Guido Governatori, Antonino Rotolo, and Shazia Sadiq.
A model of dynamic resource allocation in workflow systems. In Klaus-Dieter Schewe and Hugh E. Williams, editors, Database Technology 2004, number 27 in Conference Research and Practice of Information Technology, pages 197-206. Australian Computer Science Association, ACS, 2004. Copyright © 2004 ACS.
Abstract:Current collaborative work environments are characterized by dynamically changing organizational structures. Although there have been several efforts to refine work distribution, especially in workflow management, most literature assumes a static database approach which captures organizational roles, groups and hierarchies and implements a dynamic roles based agent assignment protocol. However, in practice only partial information may be available for organizational models, and in turn a large number of exceptions may emerge at the time of work assignment. In this paper we present an organizational model based on a policy based normative system. The model is based on a combination of an intensional logic of agency and a flexible, but computationally feasible, non-monotonic formalism (Defeasible Logic). Although this paper focuses on the model specification, the proposed approach to modelling agent societies provides a means of reasoning with partial and unpredictable information as is typical of organizational agents in workflow systems.
 
Guido Governatori, Antonino Rotolo, and Giovanni Sartor.
Temporalised normative positions in defeasible logic. In Anne Gardner, editor, Procedings of the 10th International Conference on Artificial Intelligence and Law, ACM Press, 6-10 June 2005, Copyright © 2005 ACM.
Abstract:We propose a computationally oriented non-monotonic multi-modal logic arising from the combination of temporalised agency and temporalised normative positions. We argue about the defeasible nature of these notions and then we show how to represent and reason with them in the setting of Defeasible Logic.
 
Guido Governatori, Subhasis Thakur, and Duy Hoang Pham.
A compliance model of trust. In Enrico Francesconi, Giovani Sartor, and Daniela Tiscornia, editors, Legal Knowledge and Information Systems (Jurix 2008), Frontieres in Artificial Intelligence and Applications 189, pages 118-127. IOS Press, 2008.
Abstract: We present a model of past interaction trust model based on compliance of expected behaviours.
 
Kalliopi Kravari, Grammati-Eirini Kastori, Nick Bassiliades, and Guido Governatori.
A contract agreement policy-based workflow methodology for agents interacting in the semantic web. In Mike Dean, John Hall, Antonino Rotolo, and Said Tabet, editors, RuleML 2010: 4th International Web Rule Symposium, number 6403 in LNCS, pages 223-237, Berlin, 2010. Springer. Copyrigth © 2010 Springer.
Abstract: The Semantic Web aims at automating Web content understanding and user request satisfaction. Intelligent agents assist towards this by performing complex actions on behalf of their users into real-life applications, such as e-Contracts, which make transactions simple by modeling the processes involved. This paper, presents a policy-based workflow methodology for efficient contract agreement among agents interacting in the Semantic Web. In addition, we present the integration of this methodology into a multi-agent knowledge-based framework, providing flexibility, reusability and interoperability of behavior between agents. The main advantage of our approach is that it provides a safe, generic, and reusable framework for modeling and monitoring e-Contract agreements, which could be used for different types of on-line transactions among agents. Furthermore, our framework is based on Semantic Web and FIPA standards, to maximize interoperability and reusability. Finally, an e-Commerce contract negotiation scenario is presented that illustrates the usability of the approach.
 
Efsrations Kontopoulos, Nick Bassiliades, Guido Governatori, and Grigoris Antoniou.
Extending a defeasible reasoner with modal and deontic logic operators. In 2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, pages 626-629. IEEE Press, 2008, Copyright © 2008 IEEE.
Abstract: Defeasible logic is a non-monotonic formalism that deals with incomplete and conflicting information. Modal logic deals with necessity and possibility, exhibiting defeasibility; thus, it is possible to combine defeasible logic with modal operators. This paper reports on the extension of the DR-DEVICE defeasible reasoner with modal and deontic logic operators. The aim is a practical defeasible reasoner that will take advantage of the expressiveness of modal logics and the flexibility to define diverse agent types and behaviors.
 
Ho=Pun Lam and Guido Governatori.
Towards a model of UAVs navigation in urban canyon through defeasible logic. Journal of Logic and Computation, 2011.
Abstract: This paper shows how a non-monotonic rule based system (defeasible logic) can be integrated with numerical computation engines, and how this can be applied to solve the Vehicle Routing Problem (VRP). To this end, we have simulated a physical system from which we can obtain numerical information. The physical system perceives information from its environment and generates predicates that can be reasoned by a defeasible logic engine. The conclusions/decisions derived will then realized by the physical system as it takes actions based on the conclusion derived. Here we consider a scenario where a ``flock'' of UAVs have to navigate within an urban canyon environment. The UAVs are self-autonomous without centralized control. The goal of the UAVs is to navigate to their desired destinations without colliding with each other. In case of possible collision, the UAVs concerned will communicate with each other and use their background knowledge or travel guidelines to resolve the conflicts.
 
Ho-Pun Lam, Subhasis Thakur, Guido Governatori, and Abdul Sattar.
A model to coordinate UAVs in urban environments using defeasible logic. In Yuh-Jong Hu, Ching-Long Yeh, Wolfgang Laun, Guido Governatori, John Hall, and Adrian Paschke, editors, Proceedings of the 3rd International RuleML-2009 Challenge, number 549 in CEUR Workshop Proceedings, pages 7.1-7.8, 2008.
Abstract: In this paper we show how a non-monotonic rule based system (defeasible logic) can be integrated with numerical computation engines. To this end we simulate a physical system from which we obtain numerical information. The physical system perceives information from its environment and it sends some predicates which are used by the defeasible logic reasoning engine to make decisions and then these decisions are realized by the physical system as it takes action based on the decision made by the reasoning engine. We consider a scenario where UAVs have to navigate through an urban environment. The UAVs are autonomous and there is no centralized control. The goal of the UAVs is to navigate without any collisions with each other or with any building. In case of a possible collision, the concerned UAVs communicate with each other and use background knowledge or some travel guidelines to resolve the conflicts.
 
Mehmet A. Orgun and Guido Governatori and Chuchang Liu
Modal Tableaux for Verifying Security Protocols. In Dunin-Keplicz, Barbara and Verbrugge, Rineke, editors, Formal Approaches to Multi-Agent Systems (FAMAS 2006), pages 31-46. Riva del Garda, 28-29 August, 2006.
Abstract: To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for a fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments.
 
Mehmet A. Orgun and Ji Ma and Chuchang Liu and Guido Governatori
Analysing Stream Authentication Protocols in Autonomous Agent-Based Systems. In 2nd IEEE International Symposium on Dependable, Autonomic and Secure Computing (DASC'06), pages 325-332. IEEE Press, 2006. Copyright © IEEE.
Abstract: In stream authentication protocols used for large-scale data dissemination in autonomuous systems, authentication is based on the timing of the publication of keys, and depends on trust of the receiver in the sender and belief on whether an intruder can have prior knowledge of a key before it is published by a protocol. Many existing logics and approaches have successfully been applied to specify other types of authentication protocols, but most of them are not appropriate for analysing stream authentication protocols. We therefore consider a fibred modal logic that combines a belief logic with a linear-time temporal logic which can be used to analyse time-varying aspects of certain problems. With this logical system one is able to build theories of trust for analysing stream authentication protocols, which can deal with not only agent beliefs but also the timing properties of an autonomous agent-based system.
 
Vineet Padmanabhan and Guido Governatori.
On constructing fibred tableaux for BDI logics. In Qiang Yang and Geoff Webb, editors, Ninth Pacific Rim International Conference on Artificial Intelligence, LNAI 4099, pages 150-160, Guilin, 7-11 August 2006. Springer, Copyright © 2006 Springer.
Abstract:In [x] we showed how to combine propositional BDI logics using Gabbay's fibring methodology. In this paper we extend the above mentioned works by providing a tableau-based decision procedure for the combined/fibred logics. We show how to uniformly construct a tableau calculus for the combined logic using Governatori's labelled tableau system KEM.
 
Vineet Nair Padmanabhan, Guido Governatori, and Abdul Sattar.
Actions made explicit in BDI. In Markus Stumptner, Dan Corbett, and Michael J. Brooks, editors, Advances in Artificial Intelligence, volume 2256 of LNCS, pages 390-401. Springer-Verlag, 2001, Copyright © 2001 Springer-Verlag.
Abstract: The Belief, Desire, Intention (BDI) architecture is increasingly being used in a wide range of complex applications for agents. Many theories and models exists which support this architecture and the recent version is that of Capability being added as an additional construct. In all these models the concept of action is seen in an endogenous manner. We argue that the Result of an action performed by an agent is extremely important when dealing with composite actions and hence the need for an explicit representation of them. The Capability factor is supported using a RES construct and it is shown how the components of a composite action is supported using these two. Further, we introduce an OPP (opportunity) operator which in alliance with Result and Capability provides a better semantics for practical reasoning in BDI.
 
Vineet Padmanabhan and Guido Governatori.
A Fibred Tableau Calculus for Modal Logics of Agents. In Matteo Baldoni and Ulrich Endriss, editors, Declarative Agent Languages and Technologies IV number 4327 in LNCS, pages 105-122. Berlin, 2006. Springer. Copyright © 2006 Springer. The original publication is available at www.springerlink.com.
Abstract: In [12,19] we showed how to combine propositional multimodal logics using Gabbay's fibring methodology. In this paper we extend the above mentioned works by providing a tableau-based proof technique for the combined/ fibred logics. To achieve this end we first make a comparison between two types of tableau proof systems, (graph & path), with the help of a scenario (The Friend's Puzzle). Having done that we show how to uniformly construct a tableau calculus for the combined logic using Governatori's labelled tableau system KEM. We conclude with a discussion on KEM's features.
 
Duy Hoang Pham, Guido Governatori, and Simon Raboczi.
Agents adapt to majority behaviours. In The 2008 IEEE International Conference on Research, Innovation and Vision for the Future, 2008. RIVF'08, IEEE, 2008, Copyright © 2008 IEEE.
Abstract: Agents within a group can have different perceptions of their working environment and autonomously fulfil their goals. However, they can be aware of beliefs and goals of the group as well as other members so that they can adjust their behaviours accordingly. To model these agents, we explicitly include knowledge commonly shared by the group and that obtained from other agents. By avoiding actions which violate ``mental attitudes'' shared by the majority of the group, agents demonstrate their social commitment to the group. Defeasible logic is chosen as our representation formalism for its computational efficiency, and for its ability to handle incomplete and conflicting information. Hence, our agents can enjoy the low computational cost while performing ``reasoning about others''. Finally, we present the implementation of our multi-agent system.
 
Duy Hoang Pham, Subhasis Thakur, and Guido Governatori.
Settling on the group's goals: An n-person argumentation game approach. In The Duy Bui, Tuong Vinh Ho, and Quang-Thuy Ha, editors, 11th Pacific Rim International Conference on Multi-Agents (PRIMA 2008), Lecture Notes in Computer Science 5357, pages 328-339. Springer, 2008, Copyright © 2008 Springer.
Abstract: Argumentation games have been proved to be a robust and flexible tool to resolve conflicts among agents. An agent can propose its explanation and its goal known as a claim, which can be refuted by other agents. The situation is more complicated when there are more than two agents playing the game. We propose a weighting mechanism for competing premises to tackle with conflicts from multiple agents in an n-person game. An agent can defend its proposal by giving a counter-argument to change the ``opinion'' of the majority of opposing agents. During the game, an agent can exploit the knowledge that other agents expose in order to promote and defend its main claim.
 
Duy Hoang Pham, Subhasis Thakur, and Guido Governatori.
Defeasible logic to model n-person argumentation game. In Maurice Pagnuco and Michael Thielscher, editors, Twelfth International Workshop on Non-Monotonic Reasoning, pages 215-222, 13--15 September 2008.
Abstract: In multi-agent systems, an individual agent can pursue its own goals, which may conflict with those hold by other agents. To settle on a common goal for the group of agents, the argumentation/dialogue game provides a robust and flexible tool where an agent can send its explanation for its goal in order to convince other agents. In the setting that the number of agents is greater than two and they are equally trustful, it is not clear how to extend existing argumentation/dialogue frameworks to tackle conflicts from many agents. We propose to use the defeasible logic to model the n-person argumentation game and to use the majority rule as an additional preference mechanism to tackle conflicts between arguments from individual agents.
 
Duy Hoang Pham, Guido Governatori, and Subhasis Thakur.
Extended defeasible reasoning for common goals in n-person argumentation games. Journal of Universal Computer Science, 15 no. 13 pp. 2653--2675, 2009.
Abstract: Argumentation games have been proved to be a robust and flexible tool to resolve conflicts among agents. An agent can propose its explanation and its goal known as a claim, which can be refuted by other agents. The situation is more complicated when there are more than two agents playing the game. We propose a weighting mechanism for competing premises to tackle with conflicts from multiple agents in an n-person game. An agent can defend its proposal by giving a counter-argument to change the "opinion" of the majority of opposing agents. Furthermore, using the extended defeasible reasoning an agent can exploit the knowledge that other agents expose in order to promote and defend its main claim.
 
Régis Riveret, Antonino Rotolo and Guido Governatori.
Interaction between Normative Systems and Cognitive agents in Temporal Modal Defeasible Logic. In Guido Boella, Leon van der Torre and Harko Verhagen, editors, Normative Multi-agent Systems. Dagstuhl Seminar Proceedings 7122. Internationales Begegnungs- und Forschungszentrum fuer Informatik (IBFI), Schloss Dagstuhl, Germany, Dagstuhl, Germany, 2007.
Abstract: While some recent frameworks on cognitive agents addressed the combination of mental attitudes with deontic concepts, they commonly ignore the representation of time. We propose in this paper a variant of Temporal Modal Defeasible Logic to deal in particular with temporal intervals.
 
Thomas Skylogiannis, Grigoris Antoniou, Nick Bassiliades, and Guido Governatori.
{DR-NEGOTIATE} - a system for automated agent negotiation with defeasible logic-based strategies. In Proceedings of The 2005 IEEE International Conference on e-Technology, e-Commerce and e-Service, 2005. EEE'05., pages 44-49. IEEE Press, 29 March - 1 April 2005 2005, Copyright © 2005 IEEE.
Abstract:This paper reports on a system for automated agent negotiation. It uses the JADE agent framework, and its major distinctive feature is the use of declarative negotiation strategies. The negotiation strategies are expressed in a declarative rules language, defeasible logic and are applied using the implemented defeasible reasoning system DR-DEVICE. The choice of defeasible logic is justified. The overall system architecture is described, and a particular negotiation case is presented in detail.
 
Thomas Skylogiannis, Grigoris Antoniou, Nick Bassiliades, Guido Governatori and Antonis Bikakis.
DR-NEGOTIATE — A System for Automated Agent Negotiation with Defeasible Logic-Based Strategies. Data & Knowledge Engineering: 2007. Copyright © 2007 Elsevier B.V.
Abstract: This paper reports on a system for automated agent negotiation, based on a formal and executable approach to capture the behavior of parties involved in a negotiation. It uses the JADE agent framework, and its major distinctive feature is the use of declarative negotiation strategies. The negotiation strategies are expressed in a declarative rules language, defeasible logic, and are applied using the implemented system DR-DEVICE. The key ideas and the overall system architecture are described, and a particular negotiation case is presented in detail.
 
Insu Song and Guido Governatori.
Designing Agent Chips. In 5th International Conference on Autonomous Agents and Multi-Agent Systems (AAMAS06). ACM Press, 2006.Copyright © 2006 ACM.
Abstract: We outline meta-encoding schemas for compiling nonmonotonic logic theories into Verilog HDL (Hardware Description Language) descriptions. These descriptions can be synthesized into gate level specifications for direct fabrication of silicon chips. The method is applied for designing agent chips incorporating similar features found in the BDI (Belief, Desire, and Intention) and Brooks' subsumption architectures.
 
Insu Song and Guido Governatori.
A compact argumentation system for agent system specification. In Pavlos Peppas, Anna Perini, and Loris Penserini, editors, Third European Starting AI Researcher Symposium (STAIRS 2006), pp. 26-37. Riva del Garda, 28-29 August 2006. IOS Press, Amsterdam, 2006.
Abstract: We present a non-monotonic logic tailored for specifying compact autonomous agent systems. The language is a consistent instantiation of a logic based argumentation system extended with Brooks' subsumption concept and varying degree of belief. Particularly, we present a practical implementation of the language by developing a meta-encoding method that translates logical specifications into compact general logic programs. The language allows n-ary predicate literals with the usual first-order term definitions. We show that the space complexity of the resulting general logic program is linear to the size of the original theory.
 
Insu Song, Guido Governatori, and Robert Colomb.
An interaction model for affect monitoring. In Geoff Webb and Xinghuo Yu, editors, Advances in Artificial Intelligence, number 3339 in LNAI, pages 979-984, Berlin, 2004. Copyright © 2004, Springer-Verlag. The original pubblication is available at www.springerlink.com
Abstract:This paper investigates how we can precisely define what process designers are ought achieve for what they have promised and more importantly in a way that satisfies human users. Toward these goals, an interaction model for processes and an Affect Monitoring Framework (AMF) are proposed based on our analysis on speech act theory and cognitive-based emotion models. The Affect Monitoring Framework is to detect and predict negative affects on users and to resolve caused or predicted causes of negative affects automatically.
 
Insu Song, Guido Governatori, and Joachim Diederich.
Automatic synthesis of reactive agents. In 11th International Conference on Control, Automation, Robotics and Vision, ICARCV 2010. IEEE Press, December 7-10 2010. Copyrigth © 2010 IEEE.
Abstract: This paper introduces a new approach to designing smart control chips that enables automatic synthesis of real-time control systems from agent specifications. An agent specification is compiled into a hardware description format, such as RTL-VHDL (Register Transfer Level--VLSI Hardware Description Language) or RTL Verilog, which is synthesized using computer-assisted tools to develop ASIC masks or FPGA configurations. A rule-based specification language called Layered Argumentation System (LAS) is defined and a sound and complete mapping to Verilog is developed. LAS combines fuzzy reasoning and non-monotonic reasoning. This enables chip designers to capture commonsense knowledge and concepts having varying degrees of confidence collaboratively and incrementally.
 
Insu Song, Guido Governatori, and Joachim Diederich.
Layered argumentation for fuzzy automation controllers. In IEEE Conference on Cybernetics and Intelligent Systems (CIS), , pages 189-194. IEEE Press, June 28-30 2010, Copyrigth © 2010 IEEE.
Abstract: We develop a layered argumentation system (LAS) for efficient implementation of Fuzzy automation controllers. LAS extends a logic based proposal of argumentation with subsumption concept and varying degree of confidences in beliefs. We show that this argumentation system can be used to model Fuzzy automation controllers. The argumentation system is based on a nonmonotonic logic, the computational complexity of which is known to be linear to the size of the knowledge base. LAS theories can also be mapped into RTL-VHDL (Register Transfer Level-VLSI Hardware Description Language) or RTL Verilog for very efficient hardware implementation of Fuzzy automation controllers.
 
Kaile Su, Abdul Sattar, Guido Governatori, and Qingliang Chen.
A computationally grounded logic of knowledge, belief and certainty. In Proceedings of The Fourth International Joint Conference on Autonomous Agents and Multi Agent Systems (AAMAS 2005) ACM Press, 2005, pp. 149-156. Copyright © 2005, ACM Press.
Abstract:This paper develops a logic of knowledge, belief and certainty, which allows us to explicitly mention an agent's knowledge, belief and certainty in multi-agent systems. A computationally grounded model, called interpreted KBC systems, is given for interpreting this logic. The relationship between knowledge, belief and certainty is explored. In particular, certainty entails belief; and to the agent what it is certain of appears to be knowledge. To characterize all valid formulas in our logic, we provide a sound and complete proof system. We show that the validity problem for the interpreted KBC systems is PSPACE-complete. Our proof approach is based on the well-known tableau method. To formalize those agents that are able to introspect their own belief and certainty, we identify a subclass of interpreted $KBC$ systems, called introspective KBC systems. The validity problem for introspective KBC systems turns out to be co-NP complete, and is no harder than propositional logic. We also give a sound and complete proof system with respect to the introspective KBC systems.
 
Kaile Su, Abdul Sattar, Kewen Wang, Xiangyu Luo, Guido Governatori, and Vineet Nair.
The observation-based model for BDI-agents. In Proceedings of AAAI 2005. AAAI Press, 2005, pp. 190-195. Copyright © 2005, AAAI, American Association for Artificial Intelligence.
Abstract:We present a new computational model of BDI-agents, called the observation-based BDI-model. The key point of this BDI-model is to express agents' beliefs, desires and intentions as a set of runs (computing paths), which is exactly a system in the interpreted system model, a well-known agent model due to Halpern and his colleagues. Our BDI-model is computationally grounded in that we are able to associate the BDI-agent model with a computer program, and formulas, involving agents' beliefs, desires (goals) and intentions, can be understood as properties of program computations. We present a sound and complete proof system with respect to our BDI-model and explore how symbolic model checking techniques can be applied to model checking BDI-agents. In order to make our BDI-model more flexible and practically realistic, we generalize it so that agents can have multiple sources of beliefs, goals and intentions.
 
Kaile Su, Abdul Sattar, Kewen Wang, and Guido Governatori.
Computationally grounded model of {BDI}-agents. Proceedings of IJCAI'05, 30 July - 3 August 2005,pp. 1581-1582. Copyright © 2005 IJCAI.
Abstract:We introduce a multimodal logic of belief, desire and intention, called OBDI logic, where the changes and computation of agents' beliefs, desires, and desires are based on agents' observations (i.e. local states), and we propose a model checking techniques for the logic based on interpreted systems.
 
Subhasis Thakur, Guido Governatori, Vineet Padmanabhan, and Jenny Eriksson Lundström.
Dialogue games in defeasible logic. In Mehmet A. Orgun and John Thornton, editors, 20th Australian Joint Conference on Artificial Intelligence, AI 2007, LNAI 4830, pages 497-506. Springer, 2007. Copyright © 2007 Springer.
Abstract: In this paper we show how to capture dialogue games in Defeasible Logic. We argue that Defeasible Logic is a natural candidate and general representation formalism to capture dialogue games even with requirements more complex than existing formalisms for this kind of games. We parse the dialogue into defeasible rules with time of the dialogue as time of the rule. As the dialogue evolves we allow an agent to upgrade the strength of unchallenged rules. The proof procedures of (Antoniou, Billington, Governatori, Maher 2001) are used to determine the winner of a dialogue game.
 
Miao Wang and Guido Governatori.
A Logic Framework of Normative-based Contract Management. Formal Methods in Electronic Commerce 2007. Stanford University, Palo Alto, CA. June 4, 2007.
Abstract: We explore of the feasibility of the computationally oriented institutional agency framework proposed by Governatori and Rotolo testing it against an industrial strength scenario. In particular we show how to encode in defeasible logic the dispute resolution policy described in Article 67 of FIDIC.