We present a generic denotational semantic framework for protocols for dialogs between rational and autonomous agents over action which allows for retraction and revocation of proposals for action. The semantic framework views participants in a deliberation dialog as jointly and incrementally manipulating the contents of shared spaces of action-intention tokens. The framework extends prior work by decoupling the identity of an agent who first articulates a proposal for action from the identity of any agent then empowered to retract or revoke (...) the proposal, thereby permitting proposals, entreaties, commands, promises, etc., to be distinguished semantically. (shrink)

I present a variant of with time, called, interpreted in standard Kripke semantics. On the syntactic level, is nothing but the extension of atemporal individual by: the future tense and past tense operators, and the operator of group agency for the grand coalition. A sound and complete axiomatisation for is given. Moreover, it is shown that supports reasoning about interesting normative concepts such as the concepts of achievement obligation and commitment.

This paper provides a computational framework, based on defeasible logic, to capture some aspects of institutional agency. Our background is Kanger-Lindahl-Pörn account of organised interaction, which describes this interaction within a multi-modal logical setting. This work focuses in particular on the notions of counts-as link and on those of attempt and of personal and direct action to realise states of affairs. We show how standard defeasible logic (DL) can be extended to represent these concepts: the resulting system preserves some basic (...) properties commonly attributed to them. In addition, the framework enjoys nice computational properties, as it turns out that the extension of any theory can be computed in time linear to the size of the theory itself. (shrink)

In this paper we provide a formal analysis of the idea of normative co-ordination. We argue that this idea is based on the assumption that agents can achieve flexible co-ordination by conferring normative positions to other agents. These positions include duties, permissions, and powers. In particular, we explain the idea of declarative power, which consists in the capacity of the power-holder of creating normative positions, involving other agents, simply by proclaiming such positions. In addition, we account also for the concepts (...) of representation, namely the representatives capacity of acting in the name of his principal, and of mandate, which is the mandatees duty to act as the mandator has requested. Finally, we show how the framework can be applied to represent the contract-net protocol. Some brief remarks on future research and applications conclude this contribution. (shrink)

Software agents’ ability to interact within different open systems, designed by different groups, presupposes an agreement on an unambiguous definition of a set of concepts, used to describe the context of the interaction and the communication language the agents can use. Agents’ interactions ought to allow for reliable expectations on the possible evolution of the system; however, in open systems interacting agents may not conform to predefined specifications. A possible solution is to define interaction environments including a normative component, with (...) suitable rules to regulate the behaviour of agents. To tackle this problem we propose an application-independent metamodel of artificial institutions that can be used to define open multiagent systems. In our view an artificial institution is made up by an ontology that models the social context of the interaction, a set of authorizations to act on the institutional context, a set of linguistic conventions for the performance of institutional actions and a system of norms that are necessary to constrain the agents’ actions. (shrink)

The importance of potential intentions has been demonstrated both in the construction of agent systems and in the formalisation of teamwork behaviour. However, there still lacks an adequate semantics for the notion of potential intentions as introduced by Grosz and Kraus in their SharedPlans framework. In this paper, we give a formal semantics to intentions and potential intentions, drawing upon both the representationalist approach and the accessibility-based approach. The model captures the dynamic relationship among intentions and potential intentions by providing (...) semantic rules and conditions. Also, the model treats norms as a special class of intentional context, and it is shown that norms play a critical role in the dynamics of intentions in multiagent systems. The formal semantics allows us to validate some properties that are widely-accepted for intention attitudes. (shrink)

This paper presents a framework for the generation of coherent elementary conversational sequences at the speech act level. We will embrace the notion of a cooperative dialogue game in which two players produce speech acts to transfer relevant information with respect to their commitments. Central to the approach is that participants try to achieve some sort of balanced cognitive state as a result of speech act generation and interpretation. Cognitive states of the participants change as a result of the interpretation (...) of speech acts and these changes provoke the production of a subsequent speech act. Describing the properties and the dynamics of the mental constructs that constitute the participants’ cognitive states, such as beliefs and commitments, in relation to the various dialogue contributions is an essential aspect of the game. Although simple in its basic form, the framework enables us to produce abstract conversations with some properties that agree strikingly with coherence structures found in, for instance, Conversation Analysis. (shrink)

Multi-agent systems where the agents are developed by parties with competing interests, and where there is no access to an agent’s internal state, are often classified as ‘open’. The members of such systems may inadvertently fail to, or even deliberately choose not to, conform to the system specification. Consequently, it is necessary to specify the normative relations that may exist between the members, such as permission, obligation, and institutional power. We present a framework being developed for executable specification of open (...) multi-agent systems. We adopt a bird’s eye view of these systems, as opposed to an agent’s perspective whereby it reasons about how it should act. This paper is devoted to the presentation of various examples from the NetBill protocol formalised in terms of institutional power, permission and obligation. We express the system specification in the Event Calculus and execute the specification by means of a logic programming implementation. We also give several example formalisations of sanctions for dealing with violations of permissions and obligations. We distinguish between an open multi-agent system and the procedure by which an agent enters and leaves the system. We present examples from the specification of a role-management protocol for NetBill, and demonstrate the interplay between such a protocol and the corresponding multi-agent system. (shrink)