Abstract. The ability to communicate is one of the salient properties of agents. Although a number of agent communication languages (ACLs) have been developed, obtaining a suitable formal semantics for ACLs remains one of the greatest challenges of multiagent systems theory. Previous semantics have largely been mentalistic in their orientation and are based solely on the beliefs and intentions of the participating agents. Such semantics are not suitable for most multiagent applications, which involve autonomous and heterogeneous agents, whose beliefs and intentions cannot be uniformly determined. Accordingly, we present a social semantics for ACLs that gives primacy to the interactions among the agents. Our semantics is based on social commitments and is developed in temporal logic. This semantics, because of its public orientation, is essential to providing a rigorous basis for multiagent protocols. 1

In this paper we introduce a formal framework for the construction of normative multiagent systems, based on Searle's notion of the construction of social reality. Within the structure of normative multiagent systems we distinguish between regulative norms that describe obligations, prohibitions and permissions, and constitutive norms that regulate the creation of institutional facts as well as the modification of the normative system itself. Using the metaphor of normative systems as agents, we attribute mental attitudes to the normative system. In particular,

This paper offers two main contributions. On the one hand, it establishes a general formal framework for developing a foundational ontology of socially constructed entities, in the broadest sense of this notion; on the other hand, it further contributes to understanding the ontological nature of roles. The key choice here is to put all social entities in the domain of discourse: besides social individuals, we also consider ‘reified ’ social concepts and roles, as well as their descriptions, i.e, the ‘social conventions ’ or ‘contexts ’ that define them. This allows us to formally characterize in a first-order theory the relationships among all these entities. 1

The use of the term institution has become widespread in the social sciences in recent years, reflecting the growth in institutional economics and the use of the institution concept in several other disciplines, including philosophy, sociology, politics, and geography. The term has a long history of usage in the social sciences, dating back at least to Giambattista Vico in his Scienza Nuova of 1725. However, even today, there is no unanimity in the definition of this concept. Furthermore, endless disputes over the definitions of key terms such as institution and organization have led some writers to give up matters of definition and to propose getting down somehow to practical matters instead. But it is not possible to carry out any empirical or theoretical analysis of how institutions or organizations work without having some adequate conception of what an institution or an organization is. This paper proposes that those that give up are acting in haste; potentially consensual definitions of these terms are possible, once we overcome a few obstacles and difficulties in the way. It is also important to avoid some biases in the study of institutions, where institutions and characteristics of a particular type are overgeneralized to the set

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Abstract. In this paper we use recursive modelling to formalize sanction-based obligations in a qualitative game theory. In particular, we formalize an agent who attributes mental attitudes such as goals and desires to the normative system which creates and enforces its obligations. The wishes (goals, desires) of the normative system are the commands (obligations) of the agent. Since the agent is able to reason about the normative system’s behavior, our model accounts for many ways in which an agent can violate a norm believing that it will not be sanctioned. The theory can be used in theories or applications that need a model of rational decision making in normative multiagent systems, such as for example theories of fraud and deception, trust dynamics and reputation, electronic commerce, and virtual communities. 1

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Abstract — Contracts are used to create new interaction possibilities among agents, and they therefore play an important role in the game theoretic analysis of agent interaction. We use normative multiagent systems to model both the contracts and the interactions. In particular, we formalize contracts as systems of regulative and constitutive norms within a larger rule-governed setting, and using recursive modelling we develop a game theory where agents make contracts. We show how agents can modify the behavior of normative systems by means of constitutive rules in the contract changing these systems, and we illustrate how agents use the game theory within contract negotiation in organizations. Index Terms — Contracts, qualitative game theory, multiagent systems, normative systems.

Abstract. In this paper we propose a new role for the agent metaphor in the definition of the organizational structure of multiagent systems. The agent metaphor is extended to consider as agents also social entities like organizations, groups and normative systems, so that mental attitudes can be attributed to them- beliefs, desires and goals- and also an autonomous and proactive behavior. We show how the metaphor can be applied also to structure organizations in functional areas and roles, which are described as agents too. Thus, the agent metaphor can play a role similar to the object oriented metaphor which allows structuring objects in component objects. Finally, we discuss how the agent metaphor addresses the problems of control and communication in such structured organizations. 1

Abstract. In this paper we propose an operational method for the definition of the semantics of Agent Communication Languages based on the notion of social commitment. Our proposal is suitable for open interaction frameworks where agents, designed by independent constructors, dynamically enter and leave different interaction systems. In this type of environments it is crucial to define a standard and commonly accepted semantics for the exchanged messages. We give an operational specification of commitment and introduce temporal propositions for the representation of the contents of commitments within an object-oriented paradigm. Then we use operations on commitments to define the meaning of a set of communicative acts that is complete with respect to Searle’s taxonomy of illocutionary acts, and give an example of the use of communicative acts in an interaction protocol. 1