Norms constitute a powerful coordination mechanism among heterogeneous agents. We propose means 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 the norm-oriented programming of electronic institutions: normative aspects are given a precise computational interpretation. Our formalism has been conceived as a machine language to which other higher-level normative languages can be mapped, allowing their execution, as we illustrate with a selection of examples from the literature.

Norm-governed virtual organizations define, govern and facilitate coordinated resource sharing and problem solving in societies of agents. With an explicit account of norms, openness in virtual organizations can be achieved: new components, designed by various parties, can be seamlessly accommodated. We focus on virtual organizations realised as multi-agent systems, in which human and software agents interact to achieve individual and global goals. However, any realistic account of norms should address their dynamic nature: norms will change as agents interact with each other and their environment. Due to the changing nature of norms or due to norms stemming from different virtual organizations, there will be situations when an action is simultaneously permitted and prohibited, that is, a conflict arises. Likewise, there will be situations when an action is both obliged and prohibited, that is, an inconsistency arises. We introduce an approach, based on first-order unification, to detect and resolve such conflicts and inconsistencies. In our proposed solution, we annotate a norm with the set of values their variables should not have in order to avoid a conflict or an inconsistency with another norm. Our approach neatly accommodates the domain-dependent interrelations among actions and the indirect conflicts/inconsistencies these may cause. More generally, we can capture a useful notion of inter-agent (and inter-role) delegation of actions and norms associated to them, and use it to address conflicts/inconsistencies caused by action delegation. We illustrate our approach with an e-Science example in which agents support Grid services.

Norms constitute a powerful coordination mechanism among heterogeneous agents. We propose means 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 the norm-oriented programming of electronic institutions: normative aspects are given a precise computational interpretation. Our formalism has been conceived as a machine language to which other higher-level normative languages can be mapped, allowing their execution.

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

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.

Norms (permissions, obligations and prohibitions) offer a useful and powerful abstraction with which to capture social constraints in multi-agent systems. Norms should exclude disruptive or antisocial behaviour without prescribing the design of individual agents or restricting their autonomy. An important challenge, however, in the design and management of systems governed by norms is that norms may, at times, conflict with one another; e.g, an action may be simultaneously prohibited and obliged for a particular agent. In such circumstances, agents no longer have the option of complying with these norms; whatever they do or refrain from doing will lead to a social constraint being broken. In this paper, we present mechanisms for the detection and resolution of normative conflicts. These mechanisms, based on first-order unification and constraint solving techniques, are the building blocks of more sophisticated algorithms we present for the management of normative positions, that is, the adoption and removal of permissions, obligations and prohibitions in societies of agents. We capture both direct and indirect conflicts between norms, formalise a practical concept of authority, and model conflicts that may arise as a result of delegation. We are able to formally define classic ways for resolving conflicts such as lex superior and lex posterior.

Abstract. To increase positive expectations in the outcome of open multiagent systems, institutions have been put forward to regulate agents ’ behaviour. To model and to verify such institutions, we propose to adopt the notion of status function, which provides for a unified approach to ontological and deontic aspects regulated by an institution. Also, to enhance the development of functional and rational institutions, we propose a language amenable to model checking to describe them and their properties. Finally, we present our tool and an evaluation of our approach. 1

Abstract. We present a case study which describes a ballroom as a social institution with autonomous dancer agents together with sets of norms and conventions that coordinate the behaviour of the participants. We provide a representation for the interaction protocols as finite state machines and a new way of formalising the associated norms in a logic programming language. Furthermore, we report on recent and ongoing work on an architecture for normative systems of this kind which allows agents to dynamically download interaction protocols and operational norms to guide their behaviour. Finally, we outline an alternative approach for representing the institutional state in a virtual, distributed fashion in the agents ’ private belief stores. 1

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. We present a novel mechanism for the detection and resolution of conflicts within norm-regulated virtual environments, populated by agents whose behaviours are regulated by explicit obligations, permissions and prohibitions. A conflict between norms arises when an action is simultaneously prohibited and obliged or prohibited and permitted. In this paper, we use first-order unification and constraint satisfaction to detect and resolve such conflicts, introducing a concept of norm curtailment. A flexible and robust algorithm for norm adoption is presented and aspects of indirect conflicts and conflicts across delegation of actions between agents is discussed. 1