Abstract. We develop an approach in which we model communication protocols via commitment machines. Commitment machines supply a content to protocol states and actions in terms of the social commitments of the participants. The content can be reasoned about by the agents thereby enabling flexible execution of the given protocol. We provide reasoning rules to capture the evolution of commitments through the agents ’ actions. Because of its representation of content and its operational rules, a commitment machine effectively encodes a systematically enhanced version of the original protocol, which allows the original sequences of actions as well as other legal moves to accommodate exceptions and opportunities. We show how a commitment machine can be compiled into a finite state machine for efficient execution, and prove soundness and completeness of our compilation procedure. 1

In multiagent systems, agent interaction is ruled by means of interaction protocols. Compliance to protocols can be hardwired in agent programs; however, this requires that only “certified ” agents interact. In open societies, composed of autonomous and heterogeneous agents whose internal structure is, in general, not accessible, interaction protocols should be specified in terms of the agent observable behaviour, and compliance should be verified by an external entity. In this paper, we propose a Java-Prolog-CHR system for verification of compliance of agents ’ behaviour to protocols specified in a logic-based formalism (Social Integrity Constraints). We also present the application of the formalism and the system to the specification and verification of the FIPA Contract-Net protocol.

In open societies of agents, where agents are autonomous and heterogeneous, it is not realistic to assume that agents will always act so as to comply to interaction protocols. Thus, the need arises for a formalism to specify constraints on agent interaction, and for a tool able to observe and check for agent compliance to interaction protocols. In this paper we present a Java-Prolog software component which can be used to verify compliance of agent interaction to protocols written in a logicbased formalism (Social Integrity Constraints). 1

Open multi-agent computational systems are composed of heterogeneous and possibly antagonistic software entities. Characteristic features are limited trust and unpredictable behaviour. Members of such systems may fail to, or even choose not to, conform to the norms governing their interactions. It has been argued that systems of this type should have a formal, declarative, verifiable, and meaningful semantics. We present a theoretical and computational framework being developed for the executable specification of such systems. We adopt an external perspective and view open computational systems as instances of normative systems. In this paper we demonstrate how the framework can be applied to specifying and executing an argumentation protocol based on Brewka’s reconstruction of Rescher’s theory of formal disputation. The specification is formalised in the action language C+ and executed using the ‘Causal Calculator’ (Ccalc) implementation.

Agent interaction protocols are usually specified in terms of permissible sequences of messages. This representation is, unfortunately, brittle and does not allow for flexibility and robustness. The commitment machines framework of Yolum and Singh aims to provide more flexibility and robustness by defining interactions in terms of the commitments of agents. In this paper we identify a number of areas where the commitment machines framework needs improvement and propose an improved version. In particular we improve the way in which commitments are discharged and the way in which pre-conditions are specified.

In previous work [1] we presented a framework for the specification of open computational societies i.e. societies where the behaviour of the members and their interactions cannot be predicted in advance. We viewed computational systems from an external perspective, with a focus on the institutional and the social aspects of these systems. The social constraints and roles of the open societies were specified with the use of the Event Calculus. In this paper, we formalise our framework with the use of the C+ language, a formalism with explicit state transition semantics. We use the implementation of the C+ language, the Causal Calculator, a software tool for representing commonsense knowledge about action and change, to animate and validate the specifications of computational societies. We demonstrate the utility of the Causal Calculator (by specifying and executing a Contract-Net Protocol) and comment on its functionality regarding the specification of computational societies.

Abstract. Commitments are a powerful representation for modeling multiagent interactions. Previous approaches have considered the semantics of commitments and how to check compliance with them. However, these approaches do not capture some of the subtleties that arise in real-life applications, e.g., e-commerce, where contracts and institutions have implicit temporal references. The present paper develops a rich representation for the temporal content of commitments. This enables us to capture realistic contracts and institutions rigorously, and avoid subtle ambiguities. Consequently, this approach enables us to reason about whether and when exactly a commitment is satisfied or breached and whether it is or ever becomes unenforceable. 1

An agent communication protocol specifies the rules of interaction governing a dialogue between agents in a multiagent system. In non-cooperative interactions (such as negotiation dialogues) occurring in open societies, the problem of checking an agent's conformance to such a protocol is a central issue. We identify di#erent levels of conformance (weak, exhaustive, and robust conformance) and explore, for a specific class of logic-based agents and an appropriate class of protocols, how to check an agent's conformance to a protocol a priori, purely on the basis of the agent's specification.

Abstract. For over a decade, agent research has shown that social commitments support the definition of open multiagent systems by capturing the responsibilities that agents contract toward one another through their communications. These systems, however, rely on the assumption that agents respect the social commitments they adopt. To overcome this limitation, in this paper we investigate the role of sanctions as elements whose enforcement fosters agents ’ compliance with adopted commitments. In particular, we present a model of flexible social commitments to which sanctions are attached, and where the enforcement of sanctions act as a social control mechanism for the satisfaction of commitments. 1

Although agent interaction plays a vital role in MAS, and message-centric approaches to agent interaction have their drawbacks, present agent-oriented programming languages do not provide support for implementing agent interaction that is flexible and robust. Instead, messages are provided as a primitive building block. In this paper we consider one approach for modelling agent interactions: the commitment machines framework. This framework supports modelling interactions at a higher level (using social commitments), resulting in more flexible interactions. We investigate how commitment-based interactions can be implemented in conventional agent-oriented programming languages. The contributions of this paper are: a mapping from a commitment machine to a collection of BDI-style plans; extensions to the semantics of BDI programming languages; and an examination of two issues that arise when distributing commitment machines (turn management and race conditions) and solutions to these problems. © ACM, 2007. This is the author's version of the work. It is posted here by