References of "van der Torre, Leon 50003247"
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See detailFibred security language
Boella, Guido; Gabbay, Dov M.; Genovese, Valerio UL et al

in Studia Logica (2009)

We study access control policies based on the says operator by introducing a logical framework called Fibred Security Language (FSL) which is able to deal with features like joint responsibility between ... [more ▼]

We study access control policies based on the says operator by introducing a logical framework called Fibred Security Language (FSL) which is able to deal with features like joint responsibility between sets of principals and to identify them by means of first-order formulas. FSL is based on a multimodal logic methodology. We first discuss the main contributions from the expressiveness point of view, we give semantics for the language both for classical and intuitionistic fragment), we then prove that in order to express well-known properties like ‘speaks-for’ or ‘hand-off’, defined in terms of says, we do not need second-order logic (unlike previous approaches) but a decidable fragment of first-order logic suffices. We propose a model-driven study of the says axiomatization by constraining the Kripke models in order to respect desirable security properties, we study how existing access control logics can be translated into FSL and we give completeness for the logic. [less ▲]

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See detailDynamics in Argumentation with Single Extensions: Abstraction Principles and the Grounded Extension
Boella, Guido UL; Kaci, Souhila UL; van der Torre, Leon UL

in Symbolic and Quantitative Approaches to Reasoning with Uncertainty, 10th European Conference, ECSQARU 2009, Verona, Italy, July 1-3, 2009. Proceedings (2009)

In this paper we consider the dynamics of abstract argumentation in Baroni and Giacomin’s framework for the evaluation of extension based argumentation semantics. Following Baroni and Giacomin, we do not ... [more ▼]

In this paper we consider the dynamics of abstract argumentation in Baroni and Giacomin’s framework for the evaluation of extension based argumentation semantics. Following Baroni and Giacomin, we do not consider individual approaches, but we define general principles or postulates that individual approaches may satisfy. In particular, we define abstraction principles for the attack relation, and for the arguments in the framework. We illustrate the principles on the grounded extension. In this paper we consider only principles for the single extension case, and leave the multiple extension case to further research. [less ▲]

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See detailThe role of goals in belief selection
Boella, Guido UL; Pereira, Célia Da Costa UL; Pigozzi, Gabriella UL et al

in Logic Journal of the IGPL (2009)

In this paper we consider the relation between beliefs and goals in agent theory. Beliefs play three roles in reasoning about goals: they play a role in the generation of unconditional desires from ... [more ▼]

In this paper we consider the relation between beliefs and goals in agent theory. Beliefs play three roles in reasoning about goals: they play a role in the generation of unconditional desires from conditional ones, they play a role in adoption of desires as goals, and they play a role in the selection of plans to achieve goals. In this paper we consider the role of goals in reasoning about beliefs. Though we assume that goals do not play a role in the belief generation problem, we argue that they play a role in the belief selection problem. We show the rationality of the use of goals in belief selection, in the sense that there are cases in which agents that take their goals into account in selecting a belief set from a set of alternatives outperform agents that do not do so. We also formally distinguish between the rational role of goals in belief selection and irrational wishful thinking. [less ▲]

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See detailAnalyzing Cooperation in Iterative Social Network Design
Boella, Guido UL; van der Torre, Leon UL; Villata, Serena

in Journal of Universal Computer Science (2009), 15(13),

We introduce an approach to iteratively design `small' social networks used in software engineering together with methods analyzing the cooperation in the system. The degree of cooperation is measured by ... [more ▼]

We introduce an approach to iteratively design `small' social networks used in software engineering together with methods analyzing the cooperation in the system. The degree of cooperation is measured by the emergence of coalitions and their stability over time. At the most abstract level, which we call the coalition view, coalitions are abstract entities that may dominate or attack other coalitions. During iterative design, these abstract entities are refined with agents and their dependencies constituting the coalitions (dependence view), the powers of sets of agents to see to goals (power view) and finally the beliefs, plans, tasks and goals of agents (agent view). The analysis methods predict the emergence of coalitions based on reciprocity and argumentation theory. [less ▲]

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See detailA Normative Multiagent Approach to Requirements Engineering
Boella, Guido UL; Broersen, Jan UL; van der Torre, Leon UL et al

in Postproceedings COIN@AAMAS 2009 (2009)

In this paper we present a new model, called NorMAS-RE, for the requirements analysis of a system. NorMAS-RE is a new model based on the multiagent systems paradigm with the aim to support the ... [more ▼]

In this paper we present a new model, called NorMAS-RE, for the requirements analysis of a system. NorMAS-RE is a new model based on the multiagent systems paradigm with the aim to support the requirements analysis phase of systems design. This model offers a structured approach to requirements analysis, based on conceptual models defined following a visual modeling language, called dependence networks. The main elements of this visual language are the agents with their goals, capabilities and facts, similarly to the TROPOS methodology [10]. The normative component is present both in the ontology and in the conceptual metamodel, associating agents to roles they play inside the systems and a set of goals, capabilities and facts proper of these roles. This improvement allows to define different types of dependence networks, called dynamic dependence networks and conditional dependence networks, representing the different phases of the requirements analysis of the system. This paper presents a requirements analysis model based on normative concepts such as obligation and institution. The NorMAS-RE model is a model of semiformal specification featured by an ontology, a meta-model, a graphical notation and a set of constraints. Our model, moreover, allows the definition of the notion of coalition for the different kinds of network. We present our model using the scenario of virtual organizations based on a Grid network. [less ▲]

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See detailSocial network semantics for agent communication
Boella, Guido UL; Hulstijn, Joris UL; van der Torre, Leon UL

in Social network semantics for agent communication (2009)

In this paper we introduce a semantics for agent communication languages based on social networks, providing us with a principled way to define and reason about their dynamics. As an instance we consider ... [more ▼]

In this paper we introduce a semantics for agent communication languages based on social networks, providing us with a principled way to define and reason about their dynamics. As an instance we consider dependence networks, where the social relations represent that an agent depends on another agent to achieve its intentions. We suggest how FIPA semantics can be reconstructed in this social semantics. Our approach reveals that we need special semantics for relations like ownership, authority or fear: all kinds of interesting social relations, not previously studied by multiagent systems. [less ▲]

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See detailPreference-based argumentation: Arguments supporting multiple values
Kaci, Souhila; van der Torre, Leon UL

in International Journal of Approximate Reasoning (2008), 48(3), 730751

In preference-based argumentation theory, an argument may be preferred to another one when, for example, it is more specific, its beliefs have a higher probability or certainty, or it promotes a higher ... [more ▼]

In preference-based argumentation theory, an argument may be preferred to another one when, for example, it is more specific, its beliefs have a higher probability or certainty, or it promotes a higher value. In this paper we generalize Bench-Capon’s value-based argumentation theory such that arguments can promote multiple values, and preferences among values or arguments can be specified in various ways. We assume in addition that there is default knowledge about the preferences over the arguments, and we use an algorithm to derive the most likely preference order. In particular, we show how to use non-monotonic preference reasoning to compute preferences among arguments, and subsequently the acceptable arguments, from preferences among values. We show also how the preference ordering can be used to optimize the algorithm to construct the grounded extension by proceeding from most to least preferred arguments. [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, Proceedings of the DIMACS-LAMSADE Workshop on Algorithmic Decision Theory (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 detailFrom belief change to norm change
Pigozzi, Gabriella UL; van der Torre, Leon UL

in Prague International Colloquium: Logic of change, change of logic, LOCCOL'08 (2008)

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See detailFrom belief change to preference change
Lang, Jerome; van der Torre, Leon UL

in Proceedings of Eighteenth European Conference on Artificial Intelligence (ECAI2008) (2008)

Various tasks need to consider preferences in a dynamic way. We start by discussing several possible meanings of preference change, and then focus on the one we think is the most natural: preferences ... [more ▼]

Various tasks need to consider preferences in a dynamic way. We start by discussing several possible meanings of preference change, and then focus on the one we think is the most natural: preferences evolving after some new fact has been learned. We define a family of such preference change operators, parameterized by a revision function on epistemic states and a semantics for interpreting preferences over formulas. We list some natural properties that this kind of preference change should fulfill and give conditions on the revision function and the semantics of preference for each of these properties to hold. [less ▲]

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See detailConclusion-based procedure for judgment aggregation satisfying premise independence
Pigozzi, Gabriella UL; Slavkovik, Marija UL; van der Torre, Leon UL

in Proceedings of the Eighth International Conference on Logic and the Foundations of Game and Decision Theory, LOFT 2008 (2008)

Judgment aggregation is a formal theory reasoning about how a group of agents can aggregate individual judgments on connected propositions into a collective judgment on the same propositions. Three ... [more ▼]

Judgment aggregation is a formal theory reasoning about how a group of agents can aggregate individual judgments on connected propositions into a collective judgment on the same propositions. Three procedures for successfully aggregating judgments sets are: premise-based procedure, conclusion-based procedure and distance-based merging. The conclusion-based procedure has been little investigated because it pro- vides a way to aggregate the conclusions, but not the premises, thus it outputs an incomplete judgment set. The goal of this paper is to present a conclusion-based procedure outputting complete judgment sets. [less ▲]

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See detailAdding Organizations and Roles as Primitives to JADE Framework
Genovese, Valerio UL; Grenna, Roberto; van der Torre, Leon UL et al

in Proceedings of the 3rd International Workshop on Normative Multiagent Systems, NorMAS'08 (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 give new abilities in the context of organizations, called powers, to the agents which satisfy the requirements necessary to play the roles. As primitives to program organizations and roles we provide classes and protocols which enable an agent to enact a new role in an organization and to interact with the role by invoking the execution of powers, and to receive new goals to be fulfilled. Roles have state and behaviour, thus, they are instances of classes and are strictly connected with the organization offering them. Since roles and organizations can be on a different platform with respect to the role player, the communication with them happens via protocols. Moreover, since, besides using protocols, roles and organizations can have complex behaviours, they are implemented by extending the JADE agent class. [less ▲]

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See detailSubstantive and procedural norms in normative multiagent systems
Boella, Guido; van der Torre, Leon UL

in Journal of Applied Logic (2008), 6(2), 152171

Procedural norms are instrumental norms addressed to agents playing a role in the normative system, for example to motivate these role playing agents to recognize violations or to apply sanctions ... [more ▼]

Procedural norms are instrumental norms addressed to agents playing a role in the normative system, for example to motivate these role playing agents to recognize violations or to apply sanctions. Procedural norms have first been discussed in law, where they address legal practitioners such as legislators, lawyers and policemen, but they are discussed now too in normative multiagent systems to motivate software agents. Procedural norms aim to achieve the social order specified using regulative norms like obligations and permissions, and constitutive norms like counts-as obligations. In this paper we formalize procedural, regulative and constitutive norms using input/output logic enriched with an agent ontology and an abstraction hierarchy. We show how our formalization explains Castelfranchi's notion of mutual empowerment, stating that not only the agents playing a role in a normative system are empowered by the normative system, but the normative system itself is also empowered by the agents playing a role in it. In our terminology, the agents are not only institutionally empowered, but they are also delegated normative goals from the system. Together, institutional empowerment and normative goal delegation constitute a mechanism which we call delegation of power, where agents acting on behalf of the normative system become in charge of recognizing which institutional facts follow from brute facts. [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 & 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 detailReasoning With Various Kinds of Preferences: Logic, Non-Monotonicity, and Algorithms
Kaci, Souhila; van der Torre, Leon UL

in Annals of Operations Research (2008), 163(1), 89114

As systems dealing with preferences become more sophisticated, it becomes essential to deal with various kinds of preference statements and their interaction. We introduce a non-monotonic logic ... [more ▼]

As systems dealing with preferences become more sophisticated, it becomes essential to deal with various kinds of preference statements and their interaction. We introduce a non-monotonic logic distinguishing sixteen kinds of preferences, ranging from strict to loose and from careful to opportunistic, and two kinds of ways to deal with uncertainty, either optimistically or pessimistically. The classification of the various kinds of preferences is inspired by a hypothetical agent comparing the two alternatives of a preference statement. The optimistic and pessimistic way of dealing with uncertainty correspond on the one hand to considering either the best or the worst states in the comparison of the two alternatives of a preference statement, and on the other hand to the calculation of least or most specific “distinguished” preference orders from a set of preference statements. We show that each way to calculate distinguished preference orders is compatible with eight kinds of preferences, in the sense that it calculates a unique distinguished preference order for a set of such preference statements, and we provide efficient algorithms that calculate these unique distinguished preference orders. In general, optimistic kinds of preferences are compatible with optimism in calculating distinguished preference orders, and pessimistic kinds of preferences are compatible with pessimism in calculating distinguished preference orders. However, these two sets of eight kinds of preferences are not exclusive, such that some kinds of preferences can be used in both ways to calculate distinguished preference orders, and other kinds of preferences cannot be used in either of them. We also consider the merging of optimistically and pessimistically constructed distinguished preferences orders. [less ▲]

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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 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 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 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 detailE-business Outsourcing: a New Approach combining Information Rights Technologies and Agent-Based Theory on Norms
Barbini, Patrizio; Boella, Guido; Rossi, Pier-Carlo et al

in Proceedings of the International Conference on Electronic Commerce in the 21th Century (ECIC-2008) (2008)

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