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International audience; The resource-bounded alternating-time temporal logic RB±ATL combines strategic reasoning with reasoning about resources. Its model-checking problem is known to be 2EXPTIME-complete (the same as its proper extension RB±ATL$^⁎$) and fragments have been identified to lower the complexity.In this work, we consider the variant RB±ATL+ that allows for Boolean combinations of path formulae starting with single temporal operators, but restricted to a single resource, providing an interesting trade-off between temporal expressivity and resource analysis. We show that the model-checking problem for RB±ATL+ restricted to a single agent and a single resource is $\Delta_{2}^{P}$-complete, hence the same as for the standard branching-time temporal logic CTL+. In this case reasoning about resources comes at no extra computational cost. When a fixed finite set of linear-time temporal operators is considered, the model-checking problem drops to PTIME, which includes the special case of RB±ATL restricted to a single agent and a single resource. Furthermore, we show that, with an arbitrary number of agents and a fixed number of resources, the model-checking problem for RB±ATL+ can be solved in EXPTIME using a sophisticated Turing reduction to the parity game problem for alternating vector addition systems with states (AVASS).

We study the problem of verifying multi-agent systems under the assumption of bounded recall. We introduce the logic CTLKBR, a bounded-recall variant of the temporal-epistemic logic CTLK. We define and study the model checking problem against CTLK specifications under incomplete information and bounded recall and present complexity upper bounds. We present an extension of the BDD-based model checker MCMAS implementing model checking under bounded recall semantics and discuss the experimental results obtained.

International audience; Markovian systems are widely used in reinforcement learning (RL), when the successful completion of a task depends exclusively on the last interaction between an autonomous agent and its environment. Unfortunately, real-world instructions are typically complex and often better described as non-Markovian. In this paper we present an extension method that allows solving partially-observable non-Markovian reward decision processes (PONMRDPs) by solving equivalent Markovian models. This potentially facilitates Markovian-based state-of-the-art techniques, including RL, to find optimal behaviours for problems best described as PONMRDP. We provide formal optimality guarantees of our extension methods together with a counterexample illustrating that naive extensions from existing techniques in fully-observable environments cannot provide such guarantees.

We propose a notion of alternating bisimulation for strategic abilities under imperfect information. The bisimulation preserves formulas of ATL$^*$ for both the {\em objective} and {\em subjective} variants of the state-based semantics with imperfect information, which are commonly used in the modeling and verification of multi-agent systems. Furthermore, we apply the theoretical result to the verification of coercion-resistance in the ThreeBallot voting system, a voting protocol that does not use cryptography. In particular, we show that natural simplifications of an initial model of the protocol are in fact bisimulations of the original model, and therefore satisfy the same ATL$^*$ properties, including coercion-resistance. These simplifications allow the model-checking tool MCMAS to terminate on models with a larger number of voters and candidates, compared with the initial model.

Knowledge can be represented compactly in multiple ways, from a set of propositional formulas, to a Kripke model, to a database. In this paper we study the aggregation of information coming from multiple sources, each source submitting a database modelled as a first-order relational structure. In the presence of integrity constraints, we identify classes of aggregators that respect them in the aggregated database, provided these are satisfied in all individual databases. We also characterise languages for first-order queries on which the answer to a query on the aggregated database coincides with the aggregation of the answers to the query obtained on each individual database. This contribution is meant to be a first step on the application of techniques from social choice theory to knowledge representation in databases., Comment: In Proceedings TARK 2019, arXiv:1907.08335. arXiv admin note: substantial text overlap with arXiv:1802.08586

We study the semantics of knowledge in strategic reasoning. Most existing works either implicitly assume that agents do not know one another’s strategies, or that all strategies are known to all; and some works present inconsistent mixes of both features. We put forward a novel semantics for Strategy Logic with Knowledge that cleanly models whose strategies each agent knows. We study how adopting this semantics impacts agents’ knowledge and strategic ability, as well as the complexity of the model-checking problem.

A major challenge for logics for strategies is represented by their verification in contexts of imperfect information. In this contribution we advance the state of the art by approximating the verification of Alternating-time Temporal Logic (ATL) under imperfect information by using perfect information and a three-valued semantics. In particular, we develop novel automata-theoretic techniques for the linear-time logic LTL, then apply these to finding “failure” states, where the ATL specification to be model checked is undefined. Such failure states can then be fed into a refinement procedure, thus providing a sound, albeit incomplete, verification procedure.

Humans engage in informal debates on a daily basis. By expressing their opinions and ideas in an argumentative fashion, they are able to gain a deeper understanding of a given problem and in some cases, find the best possible course of actions towards resolving it. In this paper, we develop a methodology to verify debates formalised as abstract argumentation frameworks. We first present a translation from debates to transition systems. Such transition systems can model debates and represent their evolution over time using a finite set of states. We then formalise relevant debate properties using temporal and strategy logics. These formalisations, along with a debate transition system, allow us to verify whether a given debate satisfies certain properties. The verification process can be automated using model checkers. Therefore, we also measure their performance when verifying debates, and use the results to discuss the feasibility of model checking debates., Comment: Accepted for publication as full paper at the 35th ACM/SIGAPP Symposium On Applied Computing (SAC2020), KRR track

International audience; In this paper we advance the state-of-the-art on the application of second-order propositional modal logic (SOPML) in the representation of individual and group knowledge, as well as temporal and spatial reasoning. The main theoretical contributions of the paper can be summarised as follows. Firstly, we introduce the language of (multi-modal) SOPML and interpret it on a variety of different classes of Kripke frames according to the features of the accessibility relations and of the algebraic structure of the quantification domain of propositions. We provide axiomatisations for some of these classes, and show that SOPML is unaxiomatisable on the remaining classes. Secondly, we introduce novel notions of (bi)simulations and prove that they indeed preserve the interpretation of formulas in (the universal fragment of) SOPML. Then, we apply this formal machinery to study the expressiveness of Second-order Propositional Epistemic Logic (SOPEL) in representing higher-order knowledge, i.e., the knowledge agents have about other agents’ knowledge, as well as graph-theoretic notions (e.g., 3-colorability, Hamiltonian paths, etc.). The final outcome is a rich formalism to represent and reason about relevant concepts in artificial intelligence, while still having a model checking problem that is no more computationally expensive than that of the less expressive quantified boolean logic.

Model checking multi-agent systems, in which agents are distributed and thus may have different observations of the world, against strategic behaviours is known to be a complex problem in a number of settings. There are traditionally two ways of ameliorating this complexity: imposing a hierarchy on the observations of the agents, or restricting agent actions so that they are observable by all agents. We study systems of the latter kind, since they are more suitable for modelling rational agents. In particular, we define multiagent systems in which all actions are public and study the model checking problem of such systems against Strategy Logic with equality, a very rich strategic logic that can express relevant concepts such as Nash equilibria, Pareto optimality, and due to the novel addition of equality, also evolutionary stable strategies. The main result is that the corresponding model checking problem is decidable. Keywords: Strategy Logic, Multi-agent systems, Imperfect Information, Verification, Formal Methods

We introduce a logic to reason about strategic abilities in finite games under imperfect information. We interpret Alternating-time Temporal Logic on interpreted systems with final states, where agents only have partial observability of the system’s global state. We consider the model checking problem in this setting. We prove that the complexity results available for the case of infinite traces carry over to the finite traces case. We show that when only public actions are allowed, the verification problem under perfect recall becomes decidable. © 2019, Springer Nature Switzerland AG.

International audience; In recent years the area of knowledge representation and reasoning (KR&R) has witnessed a growing interest in the modelling and analysis of data-driven/data-centric systems. These are systems in which the two tenets of data and processes are given equal importance, differently from traditional approaches whereby the data content is typically abstracted away in order to make the reasoning task easier. However, if data-aware systems (DaS) are to be deployed in concrete KR&R scenarios, it is key to develop tailored verification techniques, suitable to account for both data and processes. In this contribution we consider for the first time to our knowledge the parameterised verification of DaS. In particular, we prove that – under specific assumptions – this problem is decidable by computing a suitable cut-off value. We illustrate the proposed approach with a use case from the literature on business process modelling.

In this paper we introduce Strategy Logic with Simple Goals (SL[SG]), a fragment of Strategy Logic that strictly extends Alternating-time Temporal Logic ATL by introducing arbitrary quantification over the agents' strategies. Our motivation comes from game-theoretic applications, such as expressing Stackelberg equilibria in games, coercion in voting protocols, as well as module checking for simple goals. We prove that model checking SL[SG] is P-complete, the same as ATL. Thus, the extra expressive power comes at no computational cost as far as verification is concerned. © 2019 International Joint Conferences on Artificial Intelligence. All rights reserved.

International audience; We investigate the verification of Multi-agent Systemsagainst strategic properties expressed in Alternating-timeTemporal Logic under the assumptions of imperfect information and perfect recall. To this end, we develop a three-valuedsemantics for concurrent game structures upon which we define an abstraction method. We prove that concurrent gamestructures with imperfect information admit perfect information abstractions that preserve three-valued satisfaction. Further, we present a refinement procedure to deal with caseswhere the value of a specification is undefined. We illustratethe overall procedure in a variant of the Train Gate Controllerscenario under imperfect information and perfect recall.

International audience; We develop a logic-based technique to analyse finite interactions in multi-agent systems. We introduce a semantics for Alternating-time Temporal Logic (for both perfect and imperfect recall) and its branching-time fragments in which paths are finite instead of infinite. We study validities of these logics and present optimal algorithms for their model-checking problems in the perfect recall case.

We introduce a first-order extension of dynamic logic (FO-DL), suitable to represent and reason about the behaviour of Data-aware Systems (DaS), which are systems whose data content is explicitly exhibited in the system’s description. We illustrate the expressivity of the formal framework by modelling English auctions as DaS, and by specifying relevant properties in FO-DL. Most importantly, we develop an abstraction-based verification procedure, thus proving that the model checking problem for DaS against FO-DL is actually decidable, provided some mild assumptions on the interpretationdomain.

We introduce parameterised data-aware multi-agent systems, a formalism to reason about the temporal-epistemic properties of arbitrarily large collections of homogeneous agents, each operating on an infinite data domain. We show that their parameterised verification problem is semi-decidable for classes of interest. This is demonstrated by separately addressing the unboundedness of the number of agents and the the data domain. In doing so we reduce the parameterised model checking problem for these systems to that of parameterised verification for interleaved interpreted systems. We illustrate the expressivity of the formal model by modelling English auctions with an unbounded number of bidders on unbouded data and show how the technique here introduced can be used to give formal guarantees on the resulting system behaviour.

We study a class of synchronous, perfect-recall multi-agent systemswith imperfect information and broadcasting (i.e., fully observableactions). We define an epistemic extension of strategy logic withincomplete information and the assumption of uniform and coherentstrategies. In this setting, we prove that the model checking problem,and thus rational synthesis, is decidable with non-elementarycomplexity. We exemplify the applicability of the framework on arational secret-sharing scenario.

In the typical framework for boolean games (BG) each player can change the truth value of some propositional atoms, while attempting to make her goal true. In standard BG goals are propositional formulas, whereas in iterated BG goals are formulas of Linear Temporal Logic. Both notions of BG are characterised by the fact that agents have exclusive control over their set of atoms, meaning that no two agents can control the same atom. In the present contribution we drop the exclusivity assumption and explore structures where an atom can be controlled by multiple agents. We introduce Concurrent Game Structures with Shared Propositional Control (CGS-SPC) and show that they ac- count for several classes of repeated games, including iterated boolean games, influence games, and aggregation games. Our main result shows that, as far as verification is concerned, CGS-SPC can be reduced to concurrent game structures with exclusive control. This result provides a polynomial reduction for the model checking problem of specifications in Alternating-time Temporal Logic on CGS-SPC., In Proceedings TARK 2017, arXiv:1707.08250

In this paper we introduce {\em global and local announcement logic} (GLAL), a dynamic epistemic logic with two distinct announcement operators -- $[\phi]^+_A$ and $[\phi]^-_A$ indexed to a subset $A$ of the set $Ag$ of all agents -- for global and local announcements respectively. The boundary case $[\phi]^+_{Ag}$ corresponds to the public announcement of $\phi$, as known from the literature. Unlike standard public announcements, which are {\em model transformers}, the global and local announcements are {\em pointed model transformers}. In particular, the update induced by the announcement may be different in different states of the model. Therefore, the resulting computations are trees of models, rather than the typical sequences. A consequence of our semantics is that modally bisimilar states may be distinguished in our logic. Then, we provide a stronger notion of bisimilarity and we show that it preserves modal equivalence in GLAL. Additionally, we show that GLAL is strictly more expressive than public announcement logic with common knowledge. We prove a wide range of validities for GLAL involving the interaction between dynamics and knowledge, and show that the satisfiability problem for GLAL is decidable. We illustrate the formal machinery by means of detailed epistemic scenarios., Comment: In Proceedings TARK 2017, arXiv:1707.08250

We investigate quantified interpreted systems, a computationally grounded semantics for a first-order temporal epistemic logic on linear time. We report a completeness result for the monodic fragment of a language that includes LTL modalities as well as distributed and common knowledge. We exemplify possible uses of the formalism by analysing message passing systems, a typical framework for distributed systems, in a first-order setting.

We put forward an abstraction technique, based on a three-value semantics, for the verification of epistemic properties of agents participating in a multi-agent system. First we introduce a three-value interpretation of epistemic logic, based on a notion of order defined on the information content of the local states of each agent. Then, we use the three-value semantics to introduce an abstraction technique to verify epistemic properties of agents in infinite-state multi-agent systems.

In this paper we introduce Epistemic Strategy Logic (ESL), an extension of Strategy Logic with modal operators for individual knowledge. This enhanced framework allows us to represent explicitly and to reason about the knowledge agents have of their own and other agents' strategies. We provide a semantics to ESL in terms of epistemic concurrent game models, and consider the corresponding model checking problem. We show that the complexity of model checking ESL is not worse than (non-epistemic) Strategy Logic, Comment: In Proceedings SR 2014, arXiv:1404.0414

International audience; We investigate a class of first-order temporal-epistemic logics for reasoning about multi-agent systems. We encode typical properties of systems including perfect recall, synchronicity, no learning, and having a unique initial state in terms of variants of quantified interpreted systems, a first-order extension of interpreted systems. We identify several monodic fragments of first-order temporal-epistemic logic and show their completeness with respect to their corresponding classes of quantified interpreted systems.

Artifact systems are a novel paradigm for specifying and implementing business processes described in terms of interacting modules called artifacts. Artifacts consist of data and lifecycles, accounting respectively for the relational structure of the artifacts' states and their possible evolutions over time. In this paper we put forward artifact-centric multi-agent systems, a novel formalisation of artifact systems in the context of multi-agent systems operating on them. Differently from the usual process-based models of services, the semantics we give explicitly accounts for the data structures on which artifact systems are defined. We study the model checking problem for artifact-centric multi-agent systems against specifications written in a quantified version of temporal-epistemic logic expressing the knowledge of the agents in the exchange. We begin by noting that the problem is undecidable in general. We then identify two noteworthy restrictions, one syntactical and one semantical, that enable us to find bisimilar finite abstractions and therefore reduce the model checking problem to the instance on finite models. Under these assumptions we show that the model checking problem for these systems is EXPSPACE-complete. We then introduce artifact-centric programs, compact and declarative representations of the programs governing both the artifact system and the agents. We show that, while these in principle generate infinite-state systems, under natural conditions their verification problem can be solved on finite abstractions that can be effectively computed from the programs. Finally we exemplify the theoretical results of the paper through a mainstream procurement scenario from the artifact systems literature.

We present a methodology for the automated verification of quantum protocols using MCMAS, a symbolic model checker for multi-agent systems The method is based on the logical framework developed by D'Hondt and Panangaden for investigating epistemic and temporal properties, built on the model for Distributed Measurement-based Quantum Computation (DMC), an extension of the Measurement Calculus to distributed quantum systems. We describe the translation map from DMC to interpreted systems, the typical formalism for reasoning about time and knowledge in multi-agent systems. Then, we introduce dmc2ispl, a compiler into the input language of the MCMAS model checker. We demonstrate the technique by verifying the Quantum Teleportation Protocol, and discuss the performance of the tool., Comment: In Proceedings QAPL 2012, arXiv:1207.0559

The GSM framework provides a methodology for the development of artifact-centric systems, an increasingly popular paradigm in service-oriented computing. In this paper we tackle the problem of verifying GSM programs in a multi-agent system setting. We provide an embedding from GSM into a suitable multi-agent systems semantics for reasoning about knowledge and time at the first-order level. While we observe that GSM programs generate infinite models, we isolate a large class of "amenable" systems, which we show admit finite abstractions and are therefore verifiable through model checking. We illustrate the contribution with a procurement use-case taken from the relevant business process literature.

Artifact systems are a novel paradigm for specifying and implementing business processes described in terms of interacting modules called artifacts. Artifacts consist of data and lifecycle models, accounting for the relational structure of the artifact state and its possible evolutions over time. We consider the problem of verifying artifact systems against specifications expressed in quantified temporal logic. This problem is in general undecidable. However, when artifact systems are deployed, their states can contain only a bounded number of elements. We exploit this fact to develop an abstraction technique that enables us to verify deployed artifact systems by model checking their bounded abstraction.

We investigate quantified interpreted systems, a semantics to model multi-agent systems in which the agents can reason about individuals, their properties, and relationships among them. The semantics naturally extends interpreted systems to first-order by introducing a domain of individuals. We present a first-order epistemic language interpreted on this semantics and prove soundness and completeness of the quantified modal system $QS5^{D}_n$, an axiomatisation for these structures. Finally, we exemplify the use of the logic by modeling message passing systems, a relevant class of interpreted systems analysed in epistemic logic.

We investigate quantified interpreted systems, a semantics for multiagent systems in which agents can reason about individuals, their properties, and the relationships among them. We analyse a first-order epistemic language interpreted on this semantics and show soundness and completeness of Q.S5n, an axiomatisation for these structures.

International audience; Multi-agent approach has demonstrated its benefits for complex system modeling and simulation. This article focuses on how to represent and simulate a system as a set of several interacting simulators, with a focus on the case of multi-agent simulators. This raises a major challenge: multi-agent simulators are not conceived (in general) to be used with other simulators. This article presents a preliminary study about the rigorous integration of multi-agent simulators into a co-simulation platform. The work is grounded on the Net-Logo simulator and the co-simulation platform mecsyco.

International audience; We propose in this paper a distributed method to solve the security constrained optimal power flow problem (SCOPF) that considers not only contingencies on transmission lines but also on generators.With this aim, we extend the formulation of the SCOPF problem to consider the primary frequency response of generators as well as the short term constraints of generators and transmission lines. Then, we distribute the problem among different agents and we use a decentralized decision making algorithm, based on the Alternating Direction Method of Multipliers (ADMM), to optimize the grid power supply while being resilient to violations that would occur during contingencies. Finally, we prove the effectiveness of this formulation and implementation on a simple test system.