References of "van der Torre, Leon 50003247"
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See detailSelf Adaptive Coalitions in Multiagent Systems
Boella, Guido; van der Torre, Leon UL; Villata, Serena

in Proceedings of the 2nd IEEE International Conference on Self-Adaptive and Self-Organizing Systems (SASO 2008) (2008)

Coalitions are usually defined with respect to a static framework of dependencies among agents. In this paper we propose a dynamic view of dependence networks to enable dynamic coalitions which can self ... [more ▼]

Coalitions are usually defined with respect to a static framework of dependencies among agents. In this paper we propose a dynamic view of dependence networks to enable dynamic coalitions which can self adapt to a situation by exploiting the possibility to trigger other agentspsila goals. [less ▲]

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See detailDesirable Tie-breaking Rules in Collective Decision Making
Pigozzi, Gabriella UL; Slavkovik, Marija UL; van der Torre, Leon UL

in Annales du LAMSADE (2008)

Judgment aggregation (JA) studies how to aggregate individual judgments to form collective decisions. Examples are expert panels, legal courts, boards, and councils. The problems investigated in this new ... [more ▼]

Judgment aggregation (JA) studies how to aggregate individual judgments to form collective decisions. Examples are expert panels, legal courts, boards, and councils. The problems investigated in this new field are relevant and common to many situations. Nevertheless, the existing procedures are idealized and, likewise the related problems of preference aggregation in social choice theory, the field is plagued by impossibility theorems. In this paper, we extend standard JA in order to offer a more realistic framework and to escape the impossibility results. We propose to distinguish between abstainers and neutral judgment as well as to model the notion of confidence a group member may have in the decision rule by assigning to each criterion a normalized weight. We then show how this new framework may help us to avoid indecision in most cases. [less ▲]

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See detailInstitutions with a hierarchy of authorities in distributed dynamic environments
Boella, Guido; van der Torre, Leon UL

in Artificial Intelligence and Law (2008), 16(1), 5371

A single global authority is not sufficient to regulate heterogenous agents in multiagent systems based on distributed architectures, due to idiosyncratic local situations and to the need to regulate new ... [more ▼]

A single global authority is not sufficient to regulate heterogenous agents in multiagent systems based on distributed architectures, due to idiosyncratic local situations and to the need to regulate new issues as soon as they arise. On the one hand institutions should be structured as normative systems with a hierarchy of authorities able to cope with the dynamics of local situations, but on the other hand higher authorities should be able to delimit the autonomy of lower authorities to issue valid norms. In this paper, we study the interplay of obligations and strong permissions in the context of hierarchies of authorities using input/output logic, because its explicit norm base facilitates reasoning about norm base maintenance, and it covers a variety of conditional obligations and permissions. We combine the logic with constraints, priorities and hierarchies of authorities. In this setting, we observe that Makinson and van der Torre’s notion of prohibition immunity for permissions is no longer sufficient, and we introduce a new notion of permission as exception and a new distinction between static and dynamic norms. We show how strong permissions can dynamically change an institution by adding exceptions to obligations, provide an explicit representation of what is permitted to the subjects of the normative system and allow higher level authorities to limit the power of lower level authorities to change the normative system [less ▲]

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See detailIntroduction to the special issue on normative multiagent systems
Boella, Guido; van der Torre, Leon UL; Verhagen, Harko

in Autonomous Agents & Multi-Agent Systems (2008), 17(1), 110

This special issue contains four selected and revised papers from the second international workshop on normative multiagent systems, for short NorMAS07 (Boella et al. (eds) Normative multiagent systems ... [more ▼]

This special issue contains four selected and revised papers from the second international workshop on normative multiagent systems, for short NorMAS07 (Boella et al. (eds) Normative multiagent systems. Dagstuhl seminar proceedings 07122, 2007), held at Schloss Dagstuhl, Germany, in March 2007. At the workshop a shift was identified in the research community from a legal to an interactionist view on normative multiagent systems. In this editorial we discuss the shift, examples, and 10 new challenges in this more dynamic setting, which we use to introduce the papers of this special issue. [less ▲]

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See detailMaking Others Believe What They Want
Boella, Guido; Pereira, Célia Da Costa; Tettamanzi, Andrea et al

in Artificial Intelligence in Theory and Practice II, IFIP 20th World Computer Congress, TC 12: IFIP AI 2008 Stream (2008)

We study the interplay between argumentation and belief revision within the MAS framework. When an agent uses an argument to persuade another one, he must consider not only the proposition supported by ... [more ▼]

We study the interplay between argumentation and belief revision within the MAS framework. When an agent uses an argument to persuade another one, he must consider not only the proposition supported by the argument, but also the overall impact of the argument on the beliefs of the addressee. Different arguments lead to different belief revisions by the addressee. We propose an approach whereby the best argument is defined as the one which is both rational and the most appealing to the addressee. [less ▲]

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See detailIndependence in judgment aggregation
Pigozzi, Gabriella UL; Slavkovik, Marija UL; van der Torre, Leon UL

in Proceedings of the Ninth International Meeting of the Society for Social Choice and Welfare, SCW'08 (2008)

One of the better studied properties for operators in judgment aggregation is independence, which essentially dictates that the collective judgment on one issue should not depend on the individual ... [more ▼]

One of the better studied properties for operators in judgment aggregation is independence, which essentially dictates that the collective judgment on one issue should not depend on the individual judgments given on some other issue(s) in the same agenda. Independence is a desirable property for various reasons, but unfortunately it is too strong, as, together with mild additional conditions, it implies dictatorship. We propose here a weakening of independence, named agenda separability and show that this property is discriminant, i.e., some judgment aggregation rules satisfy it, others do not. [less ▲]

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See detailHow to Program Organizations and Roles in the JADE Framework
Baldoni, Matteo; Boella, Guido UL; Genovese, Valerio UL et al

in Multiagent System Technologies, 6th German Conference, MATES 2008, Kaiserslautern, Germany, September 23-26, 2008. Proceedings (2008)

The organization metaphor is often used in the design and implementation of multiagent systems. However, few agent programming languages provide facilities to define them. Several frameworks are proposed ... [more ▼]

The organization metaphor is often used in the design and implementation of multiagent systems. However, few agent programming languages provide facilities to define them. Several frameworks are proposed to coordinate MAS with organizations, but they are not programmable with general purpose languages. In this paper we extend the JADE framework with primitives to program in Java organizations structured in roles, and to enable agents to play roles in organizations. Roles facilitate the coordination of agents inside an organization and offer new abilities (powers) in the context of organizations to the agents which satisfy the requirements necessary to play the roles. To program organizations and roles, we provide primitives which enable an agent to enact a new role in an organization to invoke powers. [less ▲]

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See detailChanging Institutional Goals and Beliefs of Autonomous Agents
Boella, Guido; van der Torre, Leon UL; Villata, Serena

in Intelligent Agents and Multi-Agent Systems, 11th Pacific Rim International Conference on Multi-Agents, PRIMA 2008, Hanoi, Vietnam, December 15-16, 2008. Proceedings (2008)

11th Pacific Rim International Conference on Multi-Agents, PRIMA 2008, Hanoi, Vietnam, December 15-16, 2008. Proceedings

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See detailReasoning about Constitutive Norms, Counts-As Conditionals, Institutions, Deadlines and Violations
Boella, Guido; Broersen, Jan; van der Torre, Leon UL

in Intelligent Agents and Multi-Agent Systems, 11th Pacific Rim International Conference on Multi-Agents, PRIMA 2008, Hanoi, Vietnam, December 15-16, 2008. Proceedings (2008)

Reasoning about norms and time is of central concern to the regulation or control of the behavior of a multi-agent system. In earlier work we introduce a representation of normative systems that ... [more ▼]

Reasoning about norms and time is of central concern to the regulation or control of the behavior of a multi-agent system. In earlier work we introduce a representation of normative systems that distinguishes between norms and the detached obligations of agents over time. In this paper we consider constitutive norms and the detached counts-as conditionals and institutional facts in this framework, we introduce deadlines in the regulative norms, and we consider the corresponding role of violations. We focus on the reasoning tasks to determine whether a constitutive or regulative norm is redundant in a normative system and whether two normative systems are equivalent. We distinguish counts-as equivalence, institutional equivalence, obligation equivalence and violation equivalence, depending on whether we are interested in all normative consequences, or only a subset of them. For the various notions of equivalence, we give sound and complete characterizations. [less ▲]

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See detailTen Philosophical Problems in Deontic Logic
Hansen, Jörg UL; Pigozzi, Gabriella UL; van der Torre, Leon UL

in Normative Multi-agent Systems (2007)

The paper discusses ten philosophical problems in deontic logic: how to formally represent norms, when a set of norms may be termed `coherent', how to deal with normative conflicts, how contrary-to-duty ... [more ▼]

The paper discusses ten philosophical problems in deontic logic: how to formally represent norms, when a set of norms may be termed `coherent', how to deal with normative conflicts, how contrary-to-duty obligations can be appropriately modeled, how dyadic deontic operators may be redefined to relate to sets of norms instead of preference relations between possible worlds, how various concepts of permission can be accommodated, how meaning postulates and counts-as conditionals can be taken into account, and how sets of norms may be revised and merged. The problems are discussed from the viewpoint of input/output logic as developed by van der Torre Makinson. We argue that norms, not ideality, should take the central position in deontic semantics, and that a semantics that represents norms, as input/output logic does, provides helpful tools for analyzing, clarifying and solving the problems of deontic logic. [less ▲]

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See detailA Game-Theoretic Approach to Normative Multi-Agent Systems
Boella, Guido UL; van der Torre, Leon UL

in Normative Multi-agent Systems (2007)

We aim to explain our own approach, and we are therefore very brief with respect to recent related approaches in the area of normative multiagent sys- tems. For these other approaches, see the special ... [more ▼]

We aim to explain our own approach, and we are therefore very brief with respect to recent related approaches in the area of normative multiagent sys- tems. For these other approaches, see the special issue on normative multiagent systems in Computational and Mathematical Organization Theory[68], these DROPS proceedings, the proceedings of the biannual workshops on deontic logic in computer science (¢EON) and of the COIN workshop series. 1The layout of this paper follows the Øve questions above, addressing each of them in a new section. [less ▲]

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See detailFIPA Communicative Acts in Defeasible Logic
Boella, Guido UL; Hulstijn, Joris UL; Governatori, Guido UL et al

in Proceedings of NRAC'07 (2007)

In agent communication languages, the inferences that can be made on the basis of a communicative action are inherently conditional, and non-monotonic. For exam- ple, a proposal only leads to a commitment ... [more ▼]

In agent communication languages, the inferences that can be made on the basis of a communicative action are inherently conditional, and non-monotonic. For exam- ple, a proposal only leads to a commitment, on the con- dition that it is accepted. And in a persuasion dialogue, assertions may later be retracted. In this paper we there- fore 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 communica- tive actions. The logic is non-monotonic, allows nested rules and mental attitudes as the content of communica- tive actions, and has an explicit way of expressing per- sistence 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 se- mantics for agent communication, focusing on inform and propose. We show how composed speech acts can be formalized, and extend the semantics with an account of persuasion [less ▲]

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See detailFrom Social Power to Social Importance
Boella, Guido UL; Sauro, Luigi UL; van der Torre, Leon UL

in Web Intelligence and Agent Systems Journal (2007), (5), 393404

In this paper we introduce a method to measure the social importance of an agent in a multiagent system, using a directed graph representing dependencies among agents to achieve their goals, so-called ... [more ▼]

In this paper we introduce a method to measure the social importance of an agent in a multiagent system, using a directed graph representing dependencies among agents to achieve their goals, so-called dependence graphs pioneered by Castelfranchi, Conte and Sichman. Our measure is derived from van den Brink and Gilles' β-measure to rank agents, using a directed graph representing an abstract dominance relation among agents. In particular, we show how to define power structures and dependence networks from the goals and skills of individual agents, and how to adapt the β-measure for such dependence networks based on their topological properties. Moreover, we show that our notion of social importance can be given an intuitive meaning: it measures the discontent of the other agents in case the agent would leave the society. [less ▲]

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See detailRelationships Meet Their Roles in Object Oriented Programming
Baldoni, Matteo UL; Boella, Guido UL; van der Torre, Leon UL

in International Symposium on Fundamentals of Software Engineering, International Symposium, FSEN 2007, Tehran, Iran, April 17-19 2007, Proceedings (2007)

In this paper we study how roles can be added to patterns modelling relationships in Object Oriented programming. Relationships can be introduced in programming languages either by reducing them to ... [more ▼]

In this paper we study how roles can be added to patterns modelling relationships in Object Oriented programming. Relationships can be introduced in programming languages either by reducing them to attributes of the objects which participate in the relationship, or by modelling the relationship itself as a class whose instances have the participants of the relationships among their attributes. However, even if roles have been recognized as an essential component of relationships, also in modelling languages like UML, they have not been introduced in Object Oriented programming when it is necessary to model relationships. Introducing roles allows to add attributes and behaviors to the participants in the relationship, rather than to the relationship itself, and to distinguish the natural types of the participants in the relationships from the roles the participants acquire in the relationships. We show how the role model of the language powerJava can be used to endow the relationship as attribute pattern with roles. [less ▲]

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See detailPremise Independence in Judgment Aggregation
Pigozzi, Gabriella UL; van der Torre, Leon UL

in Formal Models of Belief Change in Rational Agents (2007)

Judgment aggregation studies how agent opinions on logically interconnected propositions can be mapped into a collective judgment on the same propositions, and is plagued by impossibility results. In this ... [more ▼]

Judgment aggregation studies how agent opinions on logically interconnected propositions can be mapped into a collective judgment on the same propositions, and is plagued by impossibility results. In this paper we study the central notion of independence in these impossibility results. First, we argue that the distinction between the premises and conclusions play an important role in the benchmark examples of judgment aggregation. Second, we consider the notion of independence in judgment aggregation frameworks, and we observe that the distinction between premises and conclusion is not taken into account. Third, based on our analysis, we introduce independence assumptions that distinguish premises from conclusion. We show that, by introducing new operators that satisfy our independence assumptions, the problematic impossibility results no longer hold. [less ▲]

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See detailOn the Acceptability of Incompatible Arguments
Kaci, Souhila UL; van der Torre, Leon UL; Weydert, Emil UL

in Symbolic and Quantitative Approaches to Reasoning with Uncertainty, 9th European Conference, ECSQARU 2007, Hammamet, Tunisia, October 31 – November 2, 2007, Proceedings (2007)

In this paper we study the acceptability of incompatible arguments within Dung’s abstract argumentation framework. As an example we introduce an instance of Dung’s framework where arguments are ... [more ▼]

In this paper we study the acceptability of incompatible arguments within Dung’s abstract argumentation framework. As an example we introduce an instance of Dung’s framework where arguments are represented by propositional formulas and an argument attacks another one when the conjunction of their representations is inconsistent, which we characterize as a kind of symmetric attack. Since symmetric attack is known to have the drawback to collapse the various argumentation semantics, we consider also two variations. First, we consider propositional arguments distinguishing support and conclusion. Second, we introduce a preference ordering over the arguments and we define the attack relation in terms of a symmetric incompatibility relation and the preference relation. We show how to characterize preference-based argumentation using a kind of acyclic attack relation. [less ▲]

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See detailChoosing Your Beliefs
Boella, Guido UL; Pereira, Célia Da Costa UL; Pigozzi, Gabriella UL et al

in Normative Multi-agent Systems (2007)

This paper presents and discusses a novel approach to indeterministic belief revision. An indeterministic belief revision operator assumes that, when an agent is confronted with a new piece of information ... [more ▼]

This paper presents and discusses a novel approach to indeterministic belief revision. An indeterministic belief revision operator assumes that, when an agent is confronted with a new piece of information, it can revise its belief sets in more than one way. We define a rational agent not only in terms of what it believes but also of what it desires and wants to achieve. Hence, we propose that the agent's goals play a role in the choice of (possibly) one of the several available revision options. Properties of the new belief revision mechanism are also investigated. [less ▲]

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See detailPower in Norm Negotiation
Boella, Guido UL; van der Torre, Leon UL

in Agent and Multi-Agent Systems: Technologies and Applications, First KES International Symposium, KES-AMSTA 2007, Wroclaw, Poland, May 31 – June 1, 2007, Proceedings (2007)

In social mechanism design, norm negotiation creates individual or contractual obligations fulfilling goals of the agents. The social delegation cycle distinguishes among social goal negotiation ... [more ▼]

In social mechanism design, norm negotiation creates individual or contractual obligations fulfilling goals of the agents. The social delegation cycle distinguishes among social goal negotiation, obligation and sanction negotiation and norm acceptance. Power may affect norm negotiation in various ways, and we therefore introduce a new formalization of the social delegation cycle based on power and dependence, without referring to the rule structure of norms, actions, decision variables, tasks, and so on. [less ▲]

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See detailMerging Roles in Coordination and in Agent Deliberation
Boella, Guido UL; Genovese, Valerio UL; Grenna, Roberto UL et al

in PRIMA (2007)

In this paper we generalize and merge two models of roles used in multiagent systems which address complementary aspects: enacting roles and communication among roles in an organization or institution. We ... [more ▼]

In this paper we generalize and merge two models of roles used in multiagent systems which address complementary aspects: enacting roles and communication among roles in an organization or institution. We do this by proposing a metamodel of roles and specializing the metamodel to two existing models. We show how the two approaches can be integrated since they deal with complementary aspects: Boella [1] focuses on roles as a way to specify interactions among agents, and, thus, it emphasizes the public character of roles. [2] focuses instead on how roles are played, and thus it emphasizes the private aspects of roles: how the beliefs and goals of the roles become the beliefs and goals of the agents. The former approach focuses on the dynamics of roles in function of the communication process. The latter focuses on agents internal dynamics when they start playing a role or shift the role they are currently playing. [less ▲]

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See detailFormal analysis of trace conditioning
Bosse, T. UL; Jonker, C. M. UL; Los, S. A. UL et al

in Cognitive Systems Research (2007), 8(1), 3647

In the literature classical conditioning is usually described and analysed informally. If formalisation is used, this is often based on mathematical models based on difference or differential equations ... [more ▼]

In the literature classical conditioning is usually described and analysed informally. If formalisation is used, this is often based on mathematical models based on difference or differential equations. This paper explores a formal description and analysis of the process of trace conditioning, based on logical specification and analysis methods of dynamic properties of the process. Specific types of dynamic properties are global dynamic properties, describing properties of the process as a whole, or local dynamic properties, describing properties of basic steps in a conditioning process. If the latter type of properties are specified in an executable format, they provide a temporal declarative specification of a simulation model. By a software environment these local properties can be used to actually perform simulation. Global properties can be checked automatically for simulated or other traces. Using these methods the properties of conditioning processes informally expressed by Los and Van Den Heuvel [Los, S. A., & Van Den Heuvel, C. E. (2001). Intentional and unintentional contributions to non-specific preparation during reaction time foreperiods. Journal of Experimental Psychology: Human Perception and Performance, 27, 370–386] have been formalised and verified against a specification of local properties based on Machado’s [Machado, A. (1997). Learning the temporal dynamics of behaviour. Psychological Review, 104, 241–265] differential equation model. [less ▲]

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