Automatic verification of parameterised multi-agent systems

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.

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.

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.

This article describes first steps towards the formal specification and verification of multi-agent systems, through the use of temporal belief logics. The article first describes Concurrent METATEM, a multi-agent programming language, and then develops a logic that may be used to reason about Concurrent METATEM systems. The utility of this logic for specifying and verifying Concurrent METATEM systems is demonstrated through a number of examples. The article concludes with a brief discussion on the wider implications of the work, and in particular on the use of similar logics for reasoning about multi-agent systems in general.

Model checking epistemic–probabilistic logic using probabilistic interpreted systems

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.

A blockchain is a list of data blocks as a publicly distributed ledger, which are linked together using cryptography. By allowing Turing-complete programming languages to implement smart contracts, recent blockchains such as Ethereum can reduce needs in trusted intermediators, arbitrations and enforcement costs. However, subtle errors in smart contracts have induced an enormous financial loss—for examples, the DAO attack, Parity multisignature wallet attacks, and integer underflow/overflow attacks. To identify such errors in smart contracts, various researches are performed, which are based on static analysis and theorem proving. However, they only support inspection for pre-defined error patterns, or they cannot explore the whole searching space exhaustively or be fully automatic. Hence, in this paper, we propose a novel formal verification technique to analyze blockchain smart contracts by using ATL model checking. In our methodology, we represent the interaction between users and smart contracts into a two-player game and verify properties we want to check using MCMAS that is an efficient ATL model checker for multi-agent systems. Moreover, we present three case studies to show that our proposal can successfully identify subtle flaws in real world smart contracts.

Verification of multi-agent systems is a challenging task due to their dynamic nature, and the complex interactions between agents. An example of such a system is the RoboCup Soccer Simulator, where two teams of eleven independent agents play a game of football against each other. In the present article we attempt to verify a number of properties of RoboCup football teams, using a methodology involving testing. To accomplish such testing in an efficient manner we use the McErlang model checker, as it affords precise control of the scheduling of the agents, and provides convenient access to the internal states and actions of the agents of the football teams.

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.

The paper deals with the multiagent systems for the power system topology verification. Two of such multiagent systems are considered. The idea of topology verification utilized in each of them allows considering the topology verification of a whole power system as the set of many local verification processes. Each of the described multiagent systems performs the topology verification over a different protocol. Types of agent defined for these systems are different. For each of the considered multiagent systems, analysis and design are outlined using the Multiagent Systems Engineering. For their design models, the performance evaluation has been carried out. Then, a comparison of the investigated multiagent systems is made, paying special attention to their performance effectiveness.Keywordsmodelingmultiagent systeminteraction protocolsimulationpower system topology verificationperformance evaluation

Recently, the popular logical frameworks on strategy specification and verification in the multi-agent concurrent systems, such as alternating-time temporal logic and Strategy Logic (SL), mainly focus on the strategic abilities of one coalition. In them, the notion of strategy is just viewed as a pure syntax and/or semantics object, we cannot represent or reason about the internal structures of strategies, let alone strategic abilities under these ones. In this paper, based on linear dynamic logic, by extending SL, we propose a new strategic logic, named Dynamic Strategy Logic (DSL), which includes the existential/ universal quantification operators about regular expressions with test expressions. By introducing action atoms, we can specify both the evolution of time and structured strategies by means of regular expressions. Hence, in this logic, we can represent and reason about much more expressive strategic abilities under structured strategies of coalitions, and prove that DSL is more expressive than SL.

: When a distributed systems protocol is used in a particular context as part of a solution to a larger problem, additional information may be generated from the context. Such information may be used for optimization of the system, and, in the case of security protocols, may be of use to the adversary for attacks. The project conducted a case study of the application of the epistemic model checker MCK to automatically detect such optimization opportunities, and to verify that the protocol remains secure in the mode of use. The particular protocol studied was Chaum's Dining Cryptographers protocol, a security protocol that allows a single agent to anonymously transmit a signal. The context of use considered was a more general 2-phase protocol for anonymous broadcast by an arbitrary number of agents, also proposed by Chaum. The aims of the 2-phase anonymous broadcast protocol were formulated as a knowledge-based program, and an iterative process of model checking and manual counter-example guided refinement was followed to converge on implementations of this knowledge-based program in which local predicates were identified that correspond precisely to the knowledge conditions in the knowledge-based program. This analysis demonstrated that the 2-phase protocol contains some quite subtle flows of information that can be used to optimize its performance, but no violation of the anonymity property was found. As an additional contribution of the research, a formal abstraction technique was developed, and proved correct, for epistemic model checking of protocols that call the Dining Cryptographers protocol as a subroutine. Experimental results show that the optimization improves epistemic model checking performance by orders of magnitude and enables problems of larger scale to be attacked.

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.

We present MCMAS, a model checker for the verification of multi-agent systems. MCMAS supports efficient symbolic techniques for the verification of multi-agent systems against specifications representing temporal, epistemic and strategic properties. We present the underlying semantics of the specification language supported and the algorithms implemented in MCMAS, including its fairness and counterexample generation features. We provide a detailed description of the implementation. We illustrate its use by discussing a number of examples and evaluate its performance by comparing it against other model checkers for multi-agent systems on a common case study.

We further investigate the computational power of P colonies working in the maximally parallel and sequential modes. It turns out that there is a trade-off between maximal parallelism and checking programs: using checking programs (i.e. priorities on the communication rules in the programs of the agents), P colonies working in the sequential mode with a height of at most five are computationally complete, whereas when working in the maximally parallel mode, P colonies (again with height five) already obtain the same computational power without using checking programs. Moreover, when allowing an arbitrary number of programs for each agent, we can prove that P colonies with only one agent (thus these P colonies are working in the sequential mode) are already computationally complete. On the other hand, P colonies with an arbitrary number of agents working in the sequential mode, as well as even P colonies with only one agent using an arbitrary number of non-checking programs, characterize the family of Parikh sets generated by matrix grammars without appearance checking. The completeness results can also be obtained for P colonies with prescribed teams where rules work in parallel at each agent. P colonies with prescribed teams working in the t 0 mode yield computational completeness even with one agent without priorities on the teams. On the other hand, the family of Parikh sets generated by matrix grammars without appearance checking is also characterized by P colonies with prescribed teams consisting of only (at most) two sets containing exactly one evolution rule or one antiport rule when working in the modes *,=1,≥1, and ≤ k for k ≥1, in one or an arbitrary number of agents.