Abstract. In this paper we investigate two important and related aspects of the formalization of open interaction systems: how to specify norms, and how to enforce them by means of sanctions. The problem of specifying the sanctions associated with the violation of norms is crucial in an open system because, given that the compliance of autonomous agents to obligations and prohibitions cannot be taken for granted, norm enforcement is necessary to constrain the possible evolutions of the system, thus obtaining a degree of predictability that makes it rational for agents to interact with the system. In our model, norms are specified declaratively. When certain events take place, norms become active and generate pending commitments for the agents playing certain roles. Norms also specify the sanctions associated with their violation. In the paper, we analyze the concept of sanction in detail and propose a mechanism through which sanctions can be applied.

Abstract. Norms constitute a powerful coordination mechanism among heterogeneous agents. In this paper, we propose a rule language to specify and explicitly manage the normative positions of agents (permissions, prohibitions and obligations), with which distinct deontic notions and their relationships can be captured. Our rule-based formalism includes constraints for more expressiveness and precision and allows to supplement (and implement) electronic institutions with norms. We also show how some normative aspects are given computational interpretation. 1

Abstract. In this paper we propose an application-independent model for the definition of artificial institutions that can be used to define open multi-agent systems. Such a model of institutional reality makes us able also to define an objective and external semantics of a commitment-based Agent Communication Language (ACL). In particular we propose to regard an ACL as a set of conventions to act on a fragment of institutional reality, defined in the context of an artificial institution. Another contribution of the work presented in this paper is an operational definition of norms, a crucial component of artificial institutions. In fact in open systems interacting agents might not conform to the specifications. We regard norms as event-driven rules that when are fired by events happening in the system create or cancel a set of commitments. An interesting aspect of our proposal is that both the definition of the ACL and the definition of norms are based on the same notion of commitment. Therefore an agent capable of reasoning on commitments can reason on the semantics of communicative acts and on the system of norms.

Norms are widely recognised as a means of coordinating multi-agent systems. The distributed management of norms is a challenging issue and we observe a lack of truly distributed computational realisations of normative models. In order to regulate the behaviour of autonomous agents that take part in multiple, related activities, we propose a normative model, the Normative Structure (NS), an artifact that is based on the propagation of normative positions (obligations, prohibitions, permissions), as consequences of agents’ actions. Within a NS, conflicts may arise due to the dynamic nature of the MAS and the concurrency of agents ’ actions. However, ensuring conflict-freedom of a NS at design time is computationally intractable. We show this by formalising the notion of conflict, providing a mapping of NSs into Coloured Petri Nets and borrowing well-known theoretical results from that field. Since online conflict resolution is required, we present a tractable algorithm to be employed distributedly. We then demonstrate that this algorithm is paramount for the distributed enactment of a NS.

Abstract. Institutions have been proposed as a means to regulate open interaction systems by introducing a set of norms (involving deontic positions like authorizations, obligation, prohibition and permissions) and to define the ontology of the context in which agents interact. To better clarify the interdependence existing among deontic positions and the ontology defined by each institution, in this paper we propose to model institutions in terms of status functions imposed on agents and defined as aggregates of deontic positions. We present a metamodel which describes the concepts necessary to specify an institution and FIEVeL, a language that can be used to formalize institutions. Finally, we discuss how to automatically translate FIEVeL specifications into the input language of the SPIN model checker and the kind of properties that it is possible to check. 1

Abstract. Norms, that is, obligations, prohibitions and permissions, are useful abstractions to facilitate coordination in open, heterogeneous multi-agent systems. We observe a lack of distributed architectures and non-centralised computational models for norms. We propose a model, viz., normative structures, to regulate the behaviour of autonomous agents taking part in simultaneous and possibly related activities within a multiagent system. This artifact allows the propagation of normative positions (that is, the obligations, prohibitions and permissions associated to individual agents) as a consequence of agents ’ actions. Within a normative structure, conflicts may arise – one same action can be simultaneousely forbidden and obliged/permitted. This is due to the concurrent and dynamic nature of agents ’ interactions in a multi-agent system. However, ensuring conflict freedom of normative structures at design time is computationally intractable, and thus real-time conflict resolution is required: our architecture support the distributed management of normative positions, including conflict detection and resolution. 1