On the Formal Specification and Verification of Multi-Agent Systems

We develop a logic-based framework for formal specification and algorithmic verification of homogeneous and dynamic concurrent multi-agent transition systems. Homogeneity means that all agents have the same available actions at any given state and the actions have the same effects regardless of which agents perform them. The state transitions are therefore determined only by the vector of numbers of agents performing each action and are specified symbolically, by means of conditions on these numbers definable in Presburger arithmetic. The agents are divided into controllable (by the system supervisor/controller) and uncontrollable, representing the environment or adversary. Dynamicity means that the numbers of controllable and uncontrollable agents may vary throughout the system evolution, possibly at every transition. As a language for formal specification we use a suitably extended version of Alternating-time Temporal Logic, where one can specify properties of the type “a coalition of (at least) n controllable agents can ensure against (at most) m uncontrollable agents that any possible evolution of the system satisfies a given objective gamma″, where gamma is specified again as a formula of that language and each of n and m is either a fixed number or a variable that can be quantified over. We provide formal semantics to our logic {mathcal {L}}_{textsc {hdmas}} and define normal form of its formulae. We then prove that every formula in {mathcal {L}}_{textsc {hdmas}} is equivalent in the finite to one in a normal form and develop an algorithm for global model checking of formulae in normal form in finite HDMAS models, which invokes model checking truth of Presburger formulae. We establish worst case complexity estimates for the model checking algorithm and illustrate it on a running example.

During requirement specification process of software development activities, many existing systems or business process requirements have been captured using natural language or specialized tools such as UML. However, the capturing of informal requirements into formalized properties has not been taken into attention by software developers due to time and budget constraints. It is critical for the informally captured requirements to be formally specified in order to perform system verification. Formal verification checks whether a system model meets the formal specifications while validation checks whether the developed system fulfills its intended purpose. Therefore, in this paper, we present our studies of formal verification of multi agent system using model checking approach. We have utilized model checking tool in order to execute the formal verification procedures based on a particular basic theory to verify certain kind of properties of requirement specifications. We show an example of how model checking tool could support the verification of Universiti Teknologi Malaysia (UTM) multi agent online application system and conclude that the propose model checking approach will benefit multi agent system.

International audience

This paper generalises the theory of agent refinement from [1] to multi-agent systems in the presence of new coordination mechanisms extended with real time. The generalisation is such that refinement is compositional. This means that refinement at the individual level implies refinement at the multi-agent system level. Compositionality is an important property since it reduces heavily the verification process. Thus having a theory of refinement is a crucial step towards the verification of multi-agent systems' correctness.

The formalisation of rational agents is a topic of continuing interest in Artificial Intelligence. Research on this subject has held the limelight ever since the pioneering work of Moore [1980; 1984] in which knowledge and actions are considered. Over the years important contributions have been made on both informational aspects like knowledge and belief [Halpern and Moses, 1992; Meyer and van der Hoek, 1995], and motivational 1 aspects like commitments and obligations [Cohen, 1990]. Recent developments include the work on agent-oriented programming [Shoham, 1993; Thomas, 1993], the Belief-Desire-Intention architecture [Rao and Georgeff, 1991; Rao and Georgeff, 1991a; Rao and Georgeff, 1993], logics for the specification and verification of multi-agent systems [Wooldridge, 1994; Wooldridge and Fisher, 1992], logics for agents with bounded rationality [Huang, 1994; Huang et al., 1992], and cognitive robotics [Lesperance et al., 1994; Levesque, 1994].KeywordsRational AgentBelief RevisionKripke ModelDynamic LogicPropositional FormulaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

We investigate the mapping of OWL-S process models to ISPL - the system description language for MCMAS, a symbolic model checker tailored to the verification of multi agent systems. In our approach, services are viewed as agents, and service compositions as multi agent systems. We show how various composition constructs defined in OWL-S can be encoded into ISPL by using the proposed mapping rules. We use an extended version of the BravoAir process model from the OWL-S suite of examples to illustrate the technique.

In this paper we present a logic to provide a framework for the formal specification of multiagent real-time systems which allows explicit reasoning about the actions of agents, the nondeterministic model of interaction between agents and environment, the cooperation and competition of agents and the reaction time limits of a system. The logic combines Propositional Dynamic Logic PDL and Alternating-time Temporal Logic ATL and extends the formalism with reaction time constraints. We introduce a multiagent system abstract model and show how the logic can be used to specify the model properties.

Autonomous robotic systems are complex, hybrid, and often safety-critical; this makes their formal specification and verification uniquely challenging. Though commonly used, testing and simulation alone are insufficient to ensure the correctness of, or provide sufficient evidence for the certification of, autonomous robotics. Formal methods for autonomous robotics have received some attention in the literature, but no resource provides a current overview. This short paper summarises the contributions of Luckcuck 2019, which surveys the state-of-the-art in formal specification and verification for autonomous robotics.

A key problem in verification of multi-agent systems by model checking concerns the fact that the state-space of the system grows exponentially with the number of agents present. This often makes practical model checking unfeasible whenever the system contains more than a few agents. In this paper we put forward a technique to establish a cutoff result, thereby showing that systems with an arbitrary number of agents can be verified by checking a single system consisting of a number of agents equal to the cutoff of the system. While this problem is undecidable in general, we here define a class of parameterised interpreted systems and a parameterised temporal-epistemic logic for which the result can be shown. We exemplify the theoretical results on a robotic example and present an implementation of the technique as an extension of MCMAS, an open-source model checker for multi-agent systems.

Formal specification and verification of complex IoT systems’ behavior can efficiently improve the systems’ correctness and reliability. This paper presents an enhanced time behavior protocol to specify real-time components’ timed interaction behaviors in IoT systems. The protocol model bound event tokens with time consumption constraint information according to requirements of practical applications, and time-related operators are added into the model language. Visualization and verification method for composited behavior is given. An application example is introduced, and the experimental results show that the enhanced time behavior protocol-based model can be used easily to specify, visualize, and verify IoT systems’ interaction behavior and timing constraint information.

We analyse the verification problem for synchronous, perfect recall multi-agent systems with imperfect information against a specification language that includes strategic and epistemic operators. While the verification problem is undecidable, we show that if the agents' actions are public, then verification is 2exptime-complete. To illustrate the formal framework we consider two epistemic and strategic puzzles with imperfect information and public actions: the muddy children puzzle and the classic game of battleships.

This book is a celebration of Leslie Lamport's work on concurrency, interwoven in four-and-a-half decades of an evolving industry: from the introduction of the first personal computer to an era when parallel and distributed multiprocessors are abundant. His works lay formal foundations for concurrent computations executed by interconnected computers. Some of the algorithms have become standard engineering practice for fault tolerant distributed computing - distributed systems that continue to function correctly despite failures of individual components. He also developed a substantial body of work on the formal specification and verification of concurrent systems, and has contributed to the development of automated tools applying these methods. Part I consists of technical chapters of the book and a biography. The technical chapters of this book present a retrospective on Lamport's original ideas from experts in the field. Through this lens, it portrays their long-lasting impact. The chapters cover timeless notions Lamport introduced: the Bakery algorithm, atomic shared registers and sequential consistency; causality and logical time; Byzantine Agreement; state machine replication and Paxos; temporal logic of actions (TLA). The professional biography tells of Lamport's career, providing the context in which his work arose and broke new grounds, and discusses LaTeX - perhaps Lamport's most influential contribution outside the field of concurrency. This chapter gives a voice to the people behind the achievements, notably Lamport himself, and additionally the colleagues around him, who inspired, collaborated, and helped him drive worldwide impact. Part II consists of a selection of Leslie Lamport's most influential papers. This book touches on a lifetime of contributions by Leslie Lamport to the field of concurrency and on the extensive influence he had on people working in the field. It will be of value to historians of science, and to researchers and students who work in the area of concurrency and who are interested to read about the work of one of the most influential researchers in this field.

While waiting for the millennium: Formal specification and verification of concurrent systems now

In complex systems, multiple aspects interact and influence each other. A vast number of entities are present in the system. Traditional modeling and simulation techniques fail to capture interactions between loosely coupled aspects of a complex distributed system. The objective of this work is to extend a Holonic methodology by using a formal specification language based on two formalisms: Generalized Stochastic Petri Net (GSPN) and Z language. Such a specification style facilitates the modeling of organizations and the interactions between them with both reactive and functional aspects. We illustrate the suitability of our generic approach by applying it to a Distributed Industrial Maintenance Company.

Hybrid systems such as those that combine 3D virtual worlds and organization based multiagent systems add new visual and communication features for multiuser applications. The design of such hybrid and dynamic systems is a challenging task. In this paper, we propose a system that can automatically generate a 3D virtual world (VW) from an organization based multiagent system (MAS) specification that establishes the activities participants can engage on. Both shape grammar and virtual world paradigms inspired us to propose a Virtual World Grammar (VWG) to support the generation process of a virtual world design. A VWG includes semantic information about both MAS specification and shape grammar elements. This information, along with heuristics and validations, guides the VW generation producing functional designs. To support the definition and execution of a Virtual World Grammar, we have developed a so named Virtual World Builder Toolkit (VWBT). We illustrate this process by generating a 3D visualization of a virtual institution from its specification.