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See detailMeta-Argumentation part 1
Boella, Guido UL; Gabbay, Dov M. UL; van der Torre, Leon UL et al

in Studia Logica (2009)

In this paper, we introduce the methodology and techniques of meta-argumentation to model argumentation. The methodology of meta-argumentation instantiates Dung’s abstract argumentation theory with an ... [more ▼]

In this paper, we introduce the methodology and techniques of meta-argumentation to model argumentation. The methodology of meta-argumentation instantiates Dung’s abstract argumentation theory with an extended argumentation theory, and is thus based on a combination of the methodology of instantiating abstract arguments, and the methodology of extending Dung’s basic argumentation frameworks with other relations among abstract arguments. The technique of meta-argumentation applies Dung’s theory of abstract argumentation to itself, by instantiating Dung’s abstract arguments with meta-arguments using a technique called flattening. We characterize the domain of instantiation using a representation technique based on soundness and completeness. Finally, we distinguish among various instantiations using the technique of specification languages. [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 detailNormative systems in computer science. Ten guidelines for normative multiagent systems
Boella, Guido UL; Pigozzi, Gabriella UL; van der Torre, Leon UL

in Normative Multi-Agent Systems, Dagstuhl Seminar Proceedings 09121 (2009)

In this paper we introduce and discuss ten guidelines for the use of normative systems in computer science. We adopt a multiagent sys- tems perspective, because norms are used to coordinate, organize ... [more ▼]

In this paper we introduce and discuss ten guidelines for the use of normative systems in computer science. We adopt a multiagent sys- tems perspective, because norms are used to coordinate, organize, guide, regulate or control interaction among distributed autonomous systems. The first six guidelines are derived from the computer science literature. From the so-called ‘normchange’ definition of the first workshop on nor- mative multiagent systems in 2005 we derive the guidelines to motivate which definition of normative multiagent system is used, to make explicit why norms are a kind of (soft) constraints deserving special analysis, and to explain why and how norms can be changed at runtime. From the so-called ‘mechanism design’ definition of the second workshop on nor- mative multiagent systems in 2007 we derive the guidelines to discuss the use and role of norms as a mechanism in a game-theoretic setting, clarify the role of norms in the multiagent system, and to relate the no- tion of “norm” to the legal, social, or moral literature. The remaining four guidelines follow from the philosophical literature: use norms also to resolve dilemmas, and in general to coordinate, organize, guide, regulate or control interaction among agents, distinguish norms from obligations, prohibitions and permissions, use the deontic paradoxes only to illustrate the normative multiagent system, and consider regulative norms in rela- tion to other kinds of norms and other social-cognitive computer science concepts. [less ▲]

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See detailA complete conclusion-based procedure for judgment aggregation
Pigozzi, Gabriella UL; Slavkovik, Marija UL; van der Torre, Leon UL

in Proceedings of the First International Conference on Algorithmic Decision Theory (ADT) (2009)

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 provides 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 detailFour measures for the dynamics of coalitions in social networks
Boella, Guido UL; van der Torre, Leon UL; Villata, Serena

in Four measures for the dynamics of coalitions in social networks (2009)

We introduce four measures for the change of coalitions in social networks. The first one measures the change of the agents in the network over time, The second one measures the change of dependencies ... [more ▼]

We introduce four measures for the change of coalitions in social networks. The first one measures the change of the agents in the network over time, The second one measures the change of dependencies among the agents, due to addition or removal of powers and goals of the agents. The third one measures the change in normative dependencies like obligations and prohibitions introduced by norms. The fourth one measures changes in coalitions. If one of the first three measures is high, then the fourth measure is probably high too, if the change in agents and dependencies is a cause for a change in coalitions. If the first three measures are low, but the change in coalitions is high, it is due to internal processes like violations of the coalition agreements. [less ▲]

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See detailDependency in Cooperative Boolean Games
Sauro, Luigi UL; van der Torre, Leon UL; Villata, Serena

in Agent and Multi-Agent Systems: Technologies and Applications, Third KES International Symposium, KES-AMSTA 2009, Uppsala, Sweden, June 3-5, 2009. Proceedings (2009)

Cooperative boolean games are coalitional games with both goals and costs associated to actions, and dependence networks for boolean games are a kind of social networks representing how the actions of ... [more ▼]

Cooperative boolean games are coalitional games with both goals and costs associated to actions, and dependence networks for boolean games are a kind of social networks representing how the actions of other agents have an influence on the achievement of an agent’s goal. In this paper, we introduce two new types of dependence networks, called the abstract dependence network and the refined dependence network. Moreover, we show that the notion of stability is complete with respect to the solution concept of the core in the case of cooperative boolean games with costly actions. We present a reduction, called Δ-reduction, to pass from a cooperative boolean game G to game G′ without loosing solutions. [less ▲]

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See detailTime and Defeasibility in FIPA ACL Semantics
Rotolo, Antonino; Boella, Guido; Governatori, Guido et al

in Proceedings of WLIAMAS 2008 (2008)

Inferences about speech acts are often conditional, nonmonotonic, and involve the issue of time. Most agent communication languages, however, ignore these issues, due to the difficulty to combine them in ... [more ▼]

Inferences about speech acts are often conditional, nonmonotonic, 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 shows how to express a semantics for ACLs in order to make nonmonotonic inferences on the basis of speech acts. [less ▲]

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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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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 detailPartial goal satisfaction and goal change: weak and strong partial implication, logical properties, complexity
Zhou, Yi; van der Torre, Leon UL; Zhang, Yan

in Abstract book of 7th International Joint Conference on Autonomous Agents and Multiagent Systems (AAMAS 2008), Estoril, Portugal, May 12-16, 2008, Volume 1 (2008)

Partial implication semantics in the context of a background theory has been introduced to formalize partial goal satisfaction in the context of beliefs. In this paper, we introduce strong partial ... [more ▼]

Partial implication semantics in the context of a background theory has been introduced to formalize partial goal satisfaction in the context of beliefs. In this paper, we introduce strong partial implication prohibiting redundancies and weak partial implication allowing side effects, we study their semantic as well as complexity properties, and we apply the three notions of partial implication to goal change in the context of beliefs. [less ▲]

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See detailConviviality masks in multiagent systems
Caire, Patrice UL; Villata, Serena; Boella, Guido et al

in Conviviality Masks in Multiagent Systems (2008)

In this paper we study tools for conviviality to develop user-friendly multiagent systems. First, we show how to use the social-cognitive concept of conviviality in multiagent system technology by ... [more ▼]

In this paper we study tools for conviviality to develop user-friendly multiagent systems. First, we show how to use the social-cognitive concept of conviviality in multiagent system technology by relating it to agent power and social dependence networks. Second, we de- fine conviviality masks as transformations of social dependencies by hiding power relations and social structures to facilitate social interactions. Third, we introduce dynamic dependence networks to model the creation of conviviality using conviviality masks. We illustrate the use of conviviality masks with a multiagent telecon- ferencing application for virtual worlds. [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 detailSocial Viewpoints for Arguing about Coalitions
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)

Frameworks for arguing about coalitions are based on non-monotonic logic and are therefore formal and abstract, whereas social theories about agent coalitions typically are based on conceptual modeling ... [more ▼]

Frameworks for arguing about coalitions are based on non-monotonic logic and are therefore formal and abstract, whereas social theories about agent coalitions typically are based on conceptual modeling languages and therefore semi-formal and detailed. In this paper we bridge the gap between these two research areas such that social viewpoints can be used to argue about coalitions. We formally define three social viewpoints with abstraction and refinement relations among them, and we adapt an existing coalition argumentation theory to reason about the coalitions defined in the most abstract social viewpoint. [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 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 detailA Normative View on The Blocks World
Grossi, Davide UL; Gabbay, Dov M. UL; van der Torre, Leon UL

in Proceedings of the 3rd International Workshop on Normative Multiagent Systems (NorMAS'08) (2008)

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See detailConditional norms and dyadic obligations
Broersen, Jan; van der Torre, Leon UL

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

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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 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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