Norms and accountability in multi-agent societies

It is argued that norms are best understood as classes of constraints on practical reasoning, which an agent may consult either to select appropriate goals or commitments according to the circumstances, or to construct a discursive justification for a course of action after the event. We also discuss the question of how norm-conformance can be enforced in an open agent society, arguing that some form of peer pressure is needed in open agent societies lacking universally-recognised rules or any accepted authority structure. The paper includes formal specifications of some data structures that may be employed in reasoning about normative agents

A Web-Based Tool for Analysing Normative Documents in English

Our goal is to use formal methods to analyse normative documents written in English, such as privacy policies and service-level agreements. This requires the combination of a number of different elements, including information extraction from natural language, formal languages for model representation, and an interface for property specification and verification. We have worked on a collection of components for this task: a natural language extraction tool, a suitable formalism for representing such documents, an interface for building models in this formalism, and methods for answering queries asked of a given model. In this work, each of these concerns is brought together in a web-based tool, providing a single interface for analysing normative texts in English. Through the use of a running example, we describe each component and demonstrate the workflow established by our tool

Interaction and communication among autonomous agents in multiagent systems

The main goal of this doctoral thesis is to investigate a fundamental topic of research within the Multiagent Systems paradigm: the problem of defining open, heterogeneous, and dynamic interaction frameworks. That is to realize interaction systems where multiple agents can enter and leave dynamically and where no assumptions are made on the internal structure of the interacting agents. Such topic of research has received much attention in the past few years. In particular the need to realize applications where artificial agents can interact negotiate, exchange information, resources, and services has become more and more important thanks to the advent of Internet. I started my studies by developing a trading agent that took part to an international trading on-line game: the First Trading Agent Competition (TAC). During the design and development phase of the trading agent some crucial and critical troubles emerged: the problem of accurately understanding the rules that govern the different auctions; and the problem of understanding the meaning of the numerous messages. Another general problem is that the internal structure of the developed trading agent have been strongly determined by the peculiar interface of the interaction system, consequently without any changes in its code, it would not be able to take part to any other competition on the Web. Furthermore the trading agent would not have been able to exploit opportunities, to handle unexpected situations, or to reason about the rules of the various auctions, since it is not able to understand the meaning o the exchanged messages. The presence of all those problems bears out the need to find a standard common accepted way to define open interaction systems. The most important component of every interaction framework, as is remarked also by philosophical studies on human communication is the institution of language. Therefore I start to investigate the problem of defining a standard and common accepted semantics for Agent Communication Languages (ACL). The solutions proposed so far are at best partial, and are considered as unsatisfactory by a large number of specialists. In particular, they are unable to support verifiable compliance to standards and to make agents responsible for their communicative actions. Furthermore such proposals make the strong assumption that every interacting agent may be modeled as a Belief-Desire-Intention agent. What is required is an approach focused on externally observable events as opposed to the unobservable internal states of agents. Following Speech Act Theory that views language use as a form of action, I propose an operational specification for the definition of a standard ACL based on the notion of social commitment. In such a proposal the meaning of basic communicative acts is defined as the effect that it has on the social relationship between the sender and the receiver described through operation on an unambiguous, objective, and public "object": the commitment. The adoption of the notion of commitment is crucial to stabilize the interaction among agents, to create an expectation on other agents behavior, to enable agents to reason about their and other agents actions. The proposed ACL is verifiable, that is, it is possible to determine if an agent is behaving in accordance to its communicative actions; the semantics is objective, independent of the agent's internal structure, flexible and extensible, simple, yet enough expressive. A complete operational specification of an interaction framework using the proposed commitment-based ACL is presented. In particular some sample applications of how to use the proposed framework to formalize interaction protocols are reported. A list of soundness conditions to test if a protocol is sound is proposed

Contract related agents

Imperial Users onl

Towards a contract-based interoperation model

Web Services-based solutions for interoperating processes are considered to be one of the most promising technologies for achieving truly interoperable functioning in open environments. In the last three years, the specification in particular of agreements between resource / service providers and consumers, as well as protocols for their negotiation have been proposed as a possible solution for managing the resulting computing systems. In this report, the state of the art in the area of contract-based web service applications is closely studied, identifying current limitations and possibilities. On the basis of this analysis, a general model for contract specification, negotiation, agreement, execution and management is introduced. Such a model has broad applicability both in electronic business integration and distributed knowledge management systems for decision support. Initial work presented here was completed in September 2005 and is published here as background for the European Commission funded project IST CONTRACT http://www.ist-contract.org/.Postprint (published version

Formal Specification and Automatic Verification of Multi-Agent Conditional Commitments and their Applications

Modeling agent communication using social commitments in the form of obligatory contracts among intelligent agents in a multi-agent system (MAS) provides a quintessential basis for capturing flexible and declarative interactions and helps in addressing the challenge of ensuring compliance with specifications. However, on the one hand, social commitments exclusively are not able to model agent communication actions, the cornerstone of the fundamental agent communication theory, namely speech act theory. These actions provide mechanisms for dynamic interactions and enable designers to track the evolution of active commitments. On the other hand, the designers of the system cannot guarantee the emergence of expected behaviors, such as self-contained intelligent agent complies with its protocols and honors its activated commitments. Moreover, the designers might still wish to develop effective and scalable algorithms to tackle the problem of model checking complex interactions modeled by conditional commitments and conditional commitment actions and regulated by commitment-based protocols at design time. Conditional commitments are a natural and universal frame of social commitments and cope with business conditional contracts. This dissertation is in principle about addressing two open challenging issues: 1) formally defining computationally grounded semantics for agent communication messages in terms of conditional commitments and associated actions (fulfill, cancel, release, assign and delegate), which is yet to be studied; and 2) developing a symbolic algorithm dedicated to tackle the raised model checking problem and to ensure the development of correct systems. In this dissertation, we start with distinguishing between two types of conditional commitments: weak and strong. Weak conditional commitments are those that can be activated even if the antecedents will never be satisfied, while strong conditional commitments are those that can be solely activated when there is at least one possibility to satisfy their assigned antecedents. We develop a branching-time temporal logic called CTL{cc,\alpha} that extends computation tree logic (CTL) with new modalities for representing and reasoning about the two types of conditional commitments and their actions using the formalism of interpreted systems. We present a set of valid properties, a set of reasoning rules, and a set of action postulates in order to explore the capabilities of CTL{cc,\alpha}. Furthermore, we propose a new life cycle of conditional commitments. Having a new logic (CTL{cc,\alpha}), we introduce a new symbolic algorithm to tackle the problem of its model checking. Instead of developing our algorithm from scratch, we extend the standard CTL model checking algorithm with symbolic algorithms needed for new modalities. We also investigate important theoretical results (soundness and termination) of the algorithm. Given that, we completely implement our algorithm and then assemble it on top of the symbolic model checker MCMAS, developed to automatically and directly test MAS specifications. The resulting symbolic model checker is so-called MCMAS+. We extend MCMAS's input modeling and encoding language called ISPL with shared and unshared variables needed for agent interactions and with the syntactic grammar of new modalities to produce a new one called ISPL+. We also extend the MCMAS's graphical user interface to display verified models to reduce inefficient and labor-intensive processes performed by the designers. To evaluate the performance of the developed algorithm, we analyze its time and space computational complexity. The computed time and space complexity are P-complete for explicit models and PSPACE-complete for concurrent programs. Such results are positive because model checking CTL{cc,\alpha} has the same time and space complexity of model checking CTL although CTL{cc,\alpha} extends CTL. Therefore, CTL{cc,\alpha} balances between expressive power and verification efficiency. Regarding the feasibility aspect, we apply our approach in three different application domains: business interaction protocols, health care processes, and web service compositions. The MAS paradigm is successfully employed in these domains wherein a component is represented, implemented and enacted by an agent. The proposed approach improved the employed MAS paradigm by formally modeling and automatically verifying interactions among participating agents so that the bad behaviors can be detected and then eliminated or repaired at design time and the confidence on the safety, efficiency and robustness is increased. We conduct extensive experiments to evaluate the computational performance and scalability of MCMAS+ using very large case studies. The obtained results strongly confirm the theoretical findings and make MCMAS+ practical. We finally compare our approach to other available approaches and show that it outperforms such approaches in terms of execution time, memory usage and number of considered intelligent agents

Autonomous Agents for Business Process Management

Traditional approaches to managing business processes are often inadequate for large-scale organisation-wide, dynamic settings. However, since Internet and Intranet technologies have become widespread, an increasing number of business processes exhibit these properties. Therefore, a new approach is needed. To this end, we describe the motivation, conceptualization, design, and implementation of a novel agent-based business process management system. The key advance of our system is that responsibility for enacting various components of the business process is delegated to a number of autonomous problem solving agents. To enact their role, these agents typically interact and negotiate with other agents in order to coordinate their actions and to buy in the services they require. This approach leads to a system that is significantly more agile and robust than its traditional counterparts. To help demonstrate these benefits, a companion paper describes the application of our system to a real-world problem faced by British Telecom