28 Search Results for "Bertrand, Nathalie"

Document
DOI: 10.4230/LIPIcs.CONCUR.2024.13
The Power of Counting Steps in Quantitative Games

Authors: Sougata Bose, Rasmus Ibsen-Jensen, David Purser, Patrick Totzke, and Pierre Vandenhove

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
We study deterministic games of infinite duration played on graphs and focus on the strategy complexity of quantitative objectives. Such games are known to admit optimal memoryless strategies over finite graphs, but require infinite-memory strategies in general over infinite graphs. We provide new lower and upper bounds for the strategy complexity of mean-payoff and total-payoff objectives over infinite graphs, focusing on whether step-counter strategies (sometimes called Markov strategies) suffice to implement winning strategies. In particular, we show that over finitely branching arenas, three variants of limsup mean-payoff and total-payoff objectives admit winning strategies that are based either on a step counter or on a step counter and an additional bit of memory. Conversely, we show that for certain liminf total-payoff objectives, strategies resorting to a step counter and finite memory are not sufficient. For step-counter strategies, this settles the case of all classical quantitative objectives up to the second level of the Borel hierarchy.
Cite as

Sougata Bose, Rasmus Ibsen-Jensen, David Purser, Patrick Totzke, and Pierre Vandenhove. The Power of Counting Steps in Quantitative Games. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 13:1-13:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bose_et_al:LIPIcs.CONCUR.2024.13,
  author =	{Bose, Sougata and Ibsen-Jensen, Rasmus and Purser, David and Totzke, Patrick and Vandenhove, Pierre},
  title =	{{The Power of Counting Steps in Quantitative Games}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{13:1--13:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.13},
  URN =		{urn:nbn:de:0030-drops-207852},
  doi =		{10.4230/LIPIcs.CONCUR.2024.13},
  annote =	{Keywords: Games on graphs, Markov strategies, quantitative objectives, infinite-state systems}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.23
Regular Games with Imperfect Information Are Not That Regular

Authors: Laurent Doyen and Thomas Soullard

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
We consider two-player games with imperfect information and the synthesis of a randomized strategy for one player that ensures the objective is satisfied almost-surely (i.e., with probability 1), regardless of the strategy of the other player. Imperfect information is modeled by an indistinguishability relation describing the pairs of histories that the first player cannot distinguish, a generalization of the traditional model with partial observations. The game is regular if it admits a regular function whose kernel commutes with the indistinguishability relation. The synthesis of pure strategies that ensure all possible outcomes satisfy the objective is possible in regular games, by a generic reduction that holds for all objectives. While the solution for pure strategies extends to randomized strategies in the traditional model with partial observations (which is always regular), a similar reduction does not exist in the more general model. Despite that, we show that in regular games with Büchi objectives the synthesis problem is decidable for randomized strategies that ensure the outcome satisfies the objective almost-surely.
Cite as

Laurent Doyen and Thomas Soullard. Regular Games with Imperfect Information Are Not That Regular. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 23:1-23:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{doyen_et_al:LIPIcs.CONCUR.2024.23,
  author =	{Doyen, Laurent and Soullard, Thomas},
  title =	{{Regular Games with Imperfect Information Are Not That Regular}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{23:1--23:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.23},
  URN =		{urn:nbn:de:0030-drops-207953},
  doi =		{10.4230/LIPIcs.CONCUR.2024.23},
  annote =	{Keywords: Imperfect-information games, randomized strategies, synthesis}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.29
Strategic Dominance: A New Preorder for Nondeterministic Processes

Authors: Thomas A. Henzinger, Nicolas Mazzocchi, and N. Ege Saraç

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
We study the following refinement relation between nondeterministic state-transition models: model ℬ strategically dominates model 𝒜 iff every deterministic refinement of 𝒜 is language contained in some deterministic refinement of ℬ. While language containment is trace inclusion, and the (fair) simulation preorder coincides with tree inclusion, strategic dominance falls strictly between the two and can be characterized as "strategy inclusion" between 𝒜 and ℬ: every strategy that resolves the nondeterminism of 𝒜 is dominated by a strategy that resolves the nondeterminism of ℬ. Strategic dominance can be checked in 2-ExpTime by a decidable first-order Presburger logic with quantification over words and strategies, called resolver logic. We give several other applications of resolver logic, including checking the co-safety, co-liveness, and history-determinism of boolean and quantitative automata, and checking the inclusion between hyperproperties that are specified by nondeterministic boolean and quantitative automata.
Cite as

Thomas A. Henzinger, Nicolas Mazzocchi, and N. Ege Saraç. Strategic Dominance: A New Preorder for Nondeterministic Processes. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 29:1-29:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{henzinger_et_al:LIPIcs.CONCUR.2024.29,
  author =	{Henzinger, Thomas A. and Mazzocchi, Nicolas and Sara\c{c}, N. Ege},
  title =	{{Strategic Dominance: A New Preorder for Nondeterministic Processes}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{29:1--29:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.29},
  URN =		{urn:nbn:de:0030-drops-208011},
  doi =		{10.4230/LIPIcs.CONCUR.2024.29},
  annote =	{Keywords: quantitative automata, refinement relation, resolver, strategy, history-determinism}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.40
A PSPACE Algorithm for Almost-Sure Rabin Objectives in Multi-Environment MDPs

Authors: Marnix Suilen, Marck van der Vegt, and Sebastian Junges

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
Markov Decision Processes (MDPs) model systems with uncertain transition dynamics. Multiple-environment MDPs (MEMDPs) extend MDPs. They intuitively reflect finite sets of MDPs that share the same state and action spaces but differ in the transition dynamics. The key objective in MEMDPs is to find a single strategy that satisfies a given objective in every associated MDP. The main result of this paper is PSPACE-completeness for almost-sure Rabin objectives in MEMDPs. This result clarifies the complexity landscape for MEMDPs and contrasts with results for the more general class of partially observable MDPs (POMDPs), where almost-sure reachability is already EXP-complete, and almost-sure Rabin objectives are undecidable.
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Marnix Suilen, Marck van der Vegt, and Sebastian Junges. A PSPACE Algorithm for Almost-Sure Rabin Objectives in Multi-Environment MDPs. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 40:1-40:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{suilen_et_al:LIPIcs.CONCUR.2024.40,
  author =	{Suilen, Marnix and van der Vegt, Marck and Junges, Sebastian},
  title =	{{A PSPACE Algorithm for Almost-Sure Rabin Objectives in Multi-Environment MDPs}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{40:1--40:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.40},
  URN =		{urn:nbn:de:0030-drops-208120},
  doi =		{10.4230/LIPIcs.CONCUR.2024.40},
  annote =	{Keywords: Markov Decision Processes, partial observability, linear-time Objectives}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2023.1
From Consensus Research to Redbelly Network Pty Ltd (Invited Talk)

Authors: Vincent Gramoli

Published in: LIPIcs, Volume 286, 27th International Conference on Principles of Distributed Systems (OPODIS 2023)

Abstract
Designing and implementing correctly a blockchain system requires collaborations across places and research fields. Redbelly, a company across Australia, India and USA, illustrates well this idea. It started in 2005 at OPODIS, where we published the Reconfigurable Distributed Storage to replace distributed participants offering a service without disrupting its availability. This line of work [V. Gramoli et al., 2021] was instrumental to reconfigure blockchains without introducing hard forks. The research on the consensus problem we initiated at IRISA [V. Gramoli, 2022] led to rethinking PBFT-like algorithms for the context of blockchain by getting rid of the leader that can act as the bottleneck of large networks [V. Gramoli and Q. Tang, 2023]. Our work on security led to disclosing vulnerabilities in Ethereum [Parinya Ekparinya et al., 2020] and then motivated us to formally verify blockchain consensus [Nathalie Bertrand et al., 2022]. Our work at the frontier of economics [Michael Spain et al., 2019] led us to prevent front-running attacks [Pouriya Zarbafian and Vincent Gramoli, 2023] and to incentivize rational players to behave [Alejandro Ranchal-Pedrosa and Vincent Gramoli, 2022]. Our system work at Cornell and then at EPFL was foundational in experimenting blockchains across the globe [Vincent Gramoli et al., 2023]. Although not anticipated at the time, this series of work progressively led the University of Sydney and CSIRO, and later Redbelly Network Pty Ltd, to design the Redbelly Blockchain [Tyler Crain et al., 2021; Deepal Tennakoon et al., 2023], the platform of choice for compliant asset tokenisation.
Cite as

Vincent Gramoli. From Consensus Research to Redbelly Network Pty Ltd (Invited Talk). In 27th International Conference on Principles of Distributed Systems (OPODIS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 286, pp. 1:1-1:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gramoli:LIPIcs.OPODIS.2023.1,
  author =	{Gramoli, Vincent},
  title =	{{From Consensus Research to Redbelly Network Pty Ltd}},
  booktitle =	{27th International Conference on Principles of Distributed Systems (OPODIS 2023)},
  pages =	{1:1--1:2},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-308-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{286},
  editor =	{Bessani, Alysson and D\'{e}fago, Xavier and Nakamura, Junya and Wada, Koichi and Yamauchi, Yukiko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2023.1},
  URN =		{urn:nbn:de:0030-drops-194915},
  doi =		{10.4230/LIPIcs.OPODIS.2023.1},
  annote =	{Keywords: Innovations, Commercialisation}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2023.88
Checking Presence Reachability Properties on Parameterized Shared-Memory Systems

Authors: Nicolas Waldburger

Published in: LIPIcs, Volume 272, 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)

Abstract
We consider the verification of distributed systems composed of an arbitrary number of asynchronous processes. Processes are identical finite-state machines that communicate by reading from and writing to a shared memory. Beyond the standard model with finitely many registers, we tackle round-based shared-memory systems with fresh registers at each round. In the latter model, both the number of processes and the number of registers are unbounded, making verification particularly challenging. The properties studied are generic presence reachability objectives, which subsume classical questions such as safety or synchronization by expressing the presence or absence of processes in some states. In the more general round-based setting, we establish that the parameterized verification of presence reachability properties is PSPACE-complete. Moreover, for the roundless model with finitely many registers, we prove that the complexity drops down to NP-complete and we provide several natural restrictions that make the problem solvable in polynomial time.
Cite as

Nicolas Waldburger. Checking Presence Reachability Properties on Parameterized Shared-Memory Systems. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 88:1-88:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{waldburger:LIPIcs.MFCS.2023.88,
  author =	{Waldburger, Nicolas},
  title =	{{Checking Presence Reachability Properties on Parameterized Shared-Memory Systems}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{88:1--88:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-292-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{272},
  editor =	{Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.88},
  URN =		{urn:nbn:de:0030-drops-186225},
  doi =		{10.4230/LIPIcs.MFCS.2023.88},
  annote =	{Keywords: Verification, Parameterized models, Distributed algorithms}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2022.32
Semilinear Representations for Series-Parallel Atomic Congestion Games

Authors: Nathalie Bertrand, Nicolas Markey, Suman Sadhukhan, and Ocan Sankur

Published in: LIPIcs, Volume 250, 42nd IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2022)

Abstract
We consider atomic congestion games on series-parallel networks, and study the structure of the sets of Nash equilibria and social local optima on a given network when the number of players varies. We establish that these sets are definable in Presburger arithmetic and that they admit semilinear representations whose all period vectors have a common direction. As an application, we prove that the prices of anarchy and stability converge to 1 as the number of players goes to infinity, and show how to exploit these semilinear representations to compute these ratios precisely for a given network and number of players.
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Nathalie Bertrand, Nicolas Markey, Suman Sadhukhan, and Ocan Sankur. Semilinear Representations for Series-Parallel Atomic Congestion Games. In 42nd IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 250, pp. 32:1-32:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bertrand_et_al:LIPIcs.FSTTCS.2022.32,
  author =	{Bertrand, Nathalie and Markey, Nicolas and Sadhukhan, Suman and Sankur, Ocan},
  title =	{{Semilinear Representations for Series-Parallel Atomic Congestion Games}},
  booktitle =	{42nd IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2022)},
  pages =	{32:1--32:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-261-7},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{250},
  editor =	{Dawar, Anuj and Guruswami, Venkatesan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2022.32},
  URN =		{urn:nbn:de:0030-drops-174243},
  doi =		{10.4230/LIPIcs.FSTTCS.2022.32},
  annote =	{Keywords: congestion games, Nash equilibria, Presburger arithmetic, semilinear sets, price of anarchy}
}
Document
DOI: 10.4230/LIPIcs.DISC.2022.10
Holistic Verification of Blockchain Consensus

Authors: Nathalie Bertrand, Vincent Gramoli, Igor Konnov, Marijana Lazić, Pierre Tholoniat, and Josef Widder

Published in: LIPIcs, Volume 246, 36th International Symposium on Distributed Computing (DISC 2022)

Abstract
Blockchain has recently attracted the attention of the industry due, in part, to its ability to automate asset transfers. It requires distributed participants to reach a consensus on a block despite the presence of malicious (a.k.a. Byzantine) participants. Malicious participants exploit regularly weaknesses of these blockchain consensus algorithms, with sometimes devastating consequences. In fact, these weaknesses are quite common and are well illustrated by the flaws in various blockchain consensus algorithms [Pierre Tholoniat and Vincent Gramoli, 2019]. Paradoxically, until now, no blockchain consensus has been holistically verified. In this paper, we remedy this paradox by model checking for the first time a blockchain consensus used in industry. We propose a holistic approach to verify the consensus algorithm of the Red Belly Blockchain [Tyler Crain et al., 2021], for any number n of processes and any number f < n/3 of Byzantine processes. We decompose directly the algorithm pseudocode in two parts - an inner broadcast algorithm and an outer decision algorithm - each modelled as a threshold automaton [Igor Konnov et al., 2017], and we formalize their expected properties in linear-time temporal logic. We then automatically check the inner broadcasting algorithm, under a carefully identified fairness assumption. For the verification of the outer algorithm, we simplify the model of the inner algorithm by relying on its proven properties. Doing so, we formally verify, for any parameter, not only the safety properties of the Red Belly Blockchain consensus but also its liveness in less than 70 seconds.
Cite as

Nathalie Bertrand, Vincent Gramoli, Igor Konnov, Marijana Lazić, Pierre Tholoniat, and Josef Widder. Holistic Verification of Blockchain Consensus. In 36th International Symposium on Distributed Computing (DISC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 246, pp. 10:1-10:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bertrand_et_al:LIPIcs.DISC.2022.10,
  author =	{Bertrand, Nathalie and Gramoli, Vincent and Konnov, Igor and Lazi\'{c}, Marijana and Tholoniat, Pierre and Widder, Josef},
  title =	{{Holistic Verification of Blockchain Consensus}},
  booktitle =	{36th International Symposium on Distributed Computing (DISC 2022)},
  pages =	{10:1--10:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-255-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{246},
  editor =	{Scheideler, Christian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2022.10},
  URN =		{urn:nbn:de:0030-drops-172019},
  doi =		{10.4230/LIPIcs.DISC.2022.10},
  annote =	{Keywords: Model checking, automata, logic, byzantine failure}
}
Document
Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2022.113
Parameterized Safety Verification of Round-Based Shared-Memory Systems

Authors: Nathalie Bertrand, Nicolas Markey, Ocan Sankur, and Nicolas Waldburger

Published in: LIPIcs, Volume 229, 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)

Abstract
We consider the parameterized verification problem for distributed algorithms where the goal is to develop techniques to prove the correctness of a given algorithm regardless of the number of participating processes. Motivated by an asynchronous binary consensus algorithm [James Aspnes, 2002], we consider round-based distributed algorithms communicating with shared memory. A particular challenge in these systems is that 1) the number of processes is unbounded, and, more importantly, 2) there is a fresh set of registers at each round. A verification algorithm thus needs to manage both sources of infinity. In this setting, we prove that the safety verification problem, which consists in deciding whether all possible executions avoid a given error state, is PSPACE-complete. For negative instances of the safety verification problem, we also provide exponential lower and upper bounds on the minimal number of processes needed for an error execution and on the minimal round on which the error state can be covered.
Cite as

Nathalie Bertrand, Nicolas Markey, Ocan Sankur, and Nicolas Waldburger. Parameterized Safety Verification of Round-Based Shared-Memory Systems. In 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 229, pp. 113:1-113:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bertrand_et_al:LIPIcs.ICALP.2022.113,
  author =	{Bertrand, Nathalie and Markey, Nicolas and Sankur, Ocan and Waldburger, Nicolas},
  title =	{{Parameterized Safety Verification of Round-Based Shared-Memory Systems}},
  booktitle =	{49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)},
  pages =	{113:1--113:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-235-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{229},
  editor =	{Boja\'{n}czyk, Miko{\l}aj and Merelli, Emanuela and Woodruff, David P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2022.113},
  URN =		{urn:nbn:de:0030-drops-164541},
  doi =		{10.4230/LIPIcs.ICALP.2022.113},
  annote =	{Keywords: Verification, Parameterized models, Distributed algorithms}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2021.1
Distributed Algorithms: A Challenging Playground for Model Checking (Invited Talk)

Authors: Nathalie Bertrand

Published in: LIPIcs, Volume 217, 25th International Conference on Principles of Distributed Systems (OPODIS 2021)

Abstract
Distributed computing is increasingly spreading, in advanced technological applications as well as in our daily life. Failures in distributed algorithms can have important human and financial consequences, so that is is crucial to develop rigorous techniques to verify their correctness. Model checking is a model-based approach to formal verification, dating back the 80’s. It has been successfully applied first to hardware, and later to software verification. Distributed computing raises new challenges for the model checking community, and calls for the development of new verification techniques and tools. In particular, the parameterized verification paradigm is nowadays blooming to help proving automatically the correctness of distributed algorithms. In this invited talk, we present recent parameterized verification developments to automatically prove properties of some classical distributed algorithms.
Cite as

Nathalie Bertrand. Distributed Algorithms: A Challenging Playground for Model Checking (Invited Talk). In 25th International Conference on Principles of Distributed Systems (OPODIS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 217, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bertrand:LIPIcs.OPODIS.2021.1,
  author =	{Bertrand, Nathalie},
  title =	{{Distributed Algorithms: A Challenging Playground for Model Checking}},
  booktitle =	{25th International Conference on Principles of Distributed Systems (OPODIS 2021)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-219-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{217},
  editor =	{Bramas, Quentin and Gramoli, Vincent and Milani, Alessia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2021.1},
  URN =		{urn:nbn:de:0030-drops-157767},
  doi =		{10.4230/LIPIcs.OPODIS.2021.1},
  annote =	{Keywords: Verification, Distributed algorithms}
}
Document
Invited Paper
DOI: 10.4230/LIPIcs.CONCUR.2021.1
CONCUR Test-Of-Time Award 2021 (Invited Paper)

Authors: Nathalie Bertrand, Luca de Alfaro, Rob van Glabbeek, Catuscia Palamidessi, and Nobuko Yoshida

Published in: LIPIcs, Volume 203, 32nd International Conference on Concurrency Theory (CONCUR 2021)

Abstract
This short article announces the recipients of the CONCUR Test-of-Time Award 2021.
Cite as

Nathalie Bertrand, Luca de Alfaro, Rob van Glabbeek, Catuscia Palamidessi, and Nobuko Yoshida. CONCUR Test-Of-Time Award 2021 (Invited Paper). In 32nd International Conference on Concurrency Theory (CONCUR 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 203, pp. 1:1-1:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{bertrand_et_al:LIPIcs.CONCUR.2021.1,
  author =	{Bertrand, Nathalie and de Alfaro, Luca and van Glabbeek, Rob and Palamidessi, Catuscia and Yoshida, Nobuko},
  title =	{{CONCUR Test-Of-Time Award 2021}},
  booktitle =	{32nd International Conference on Concurrency Theory (CONCUR 2021)},
  pages =	{1:1--1:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-203-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{203},
  editor =	{Haddad, Serge and Varacca, Daniele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2021.1},
  URN =		{urn:nbn:de:0030-drops-143786},
  doi =		{10.4230/LIPIcs.CONCUR.2021.1},
  annote =	{Keywords: Concurrency, CONCUR Test-of-Time Award}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2021.7
Quantified Linear Temporal Logic over Probabilistic Systems with an Application to Vacuity Checking

Authors: Jakob Piribauer, Christel Baier, Nathalie Bertrand, and Ocan Sankur

Published in: LIPIcs, Volume 203, 32nd International Conference on Concurrency Theory (CONCUR 2021)

Abstract
Quantified linear temporal logic (QLTL) is an ω-regular extension of LTL allowing quantification over propositional variables. We study the model checking problem of QLTL-formulas over Markov chains and Markov decision processes (MDPs) with respect to the number of quantifier alternations of formulas in prenex normal form. For formulas with k{-}1 quantifier alternations, we prove that all qualitative and quantitative model checking problems are k-EXPSPACE-complete over Markov chains and k{+}1-EXPTIME-complete over MDPs. As an application of these results, we generalize vacuity checking for LTL specifications from the non-probabilistic to the probabilistic setting. We show how to check whether an LTL-formula is affected by a subformula, and also study inherent vacuity for probabilistic systems.
Cite as

Jakob Piribauer, Christel Baier, Nathalie Bertrand, and Ocan Sankur. Quantified Linear Temporal Logic over Probabilistic Systems with an Application to Vacuity Checking. In 32nd International Conference on Concurrency Theory (CONCUR 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 203, pp. 7:1-7:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{piribauer_et_al:LIPIcs.CONCUR.2021.7,
  author =	{Piribauer, Jakob and Baier, Christel and Bertrand, Nathalie and Sankur, Ocan},
  title =	{{Quantified Linear Temporal Logic over Probabilistic Systems with an Application to Vacuity Checking}},
  booktitle =	{32nd International Conference on Concurrency Theory (CONCUR 2021)},
  pages =	{7:1--7:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-203-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{203},
  editor =	{Haddad, Serge and Varacca, Daniele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2021.7},
  URN =		{urn:nbn:de:0030-drops-143842},
  doi =		{10.4230/LIPIcs.CONCUR.2021.7},
  annote =	{Keywords: Quantified linear temporal logic, Markov chain, Markov decision process, vacuity}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2021.15
Guard Automata for the Verification of Safety and Liveness of Distributed Algorithms

Authors: Nathalie Bertrand, Bastien Thomas, and Josef Widder

Published in: LIPIcs, Volume 203, 32nd International Conference on Concurrency Theory (CONCUR 2021)

Abstract
Distributed algorithms typically run over arbitrary many processes and may involve unboundedly many rounds, making the automated verification of their correctness challenging. Building on domain theory, we introduce a framework that abstracts infinite-state distributed systems that represent distributed algorithms into finite-state guard automata. The soundness of the approach corresponds to the Scott-continuity of the abstraction, which relies on the assumption that the distributed algorithms are layered. Guard automata thus enable the verification of safety and liveness properties of distributed algorithms.
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Nathalie Bertrand, Bastien Thomas, and Josef Widder. Guard Automata for the Verification of Safety and Liveness of Distributed Algorithms. In 32nd International Conference on Concurrency Theory (CONCUR 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 203, pp. 15:1-15:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{bertrand_et_al:LIPIcs.CONCUR.2021.15,
  author =	{Bertrand, Nathalie and Thomas, Bastien and Widder, Josef},
  title =	{{Guard Automata for the Verification of Safety and Liveness of Distributed Algorithms}},
  booktitle =	{32nd International Conference on Concurrency Theory (CONCUR 2021)},
  pages =	{15:1--15:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-203-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{203},
  editor =	{Haddad, Serge and Varacca, Daniele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2021.15},
  URN =		{urn:nbn:de:0030-drops-143926},
  doi =		{10.4230/LIPIcs.CONCUR.2021.15},
  annote =	{Keywords: Verification, Distributed algorithms, Domain theory}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2020.39
Synthesizing Safe Coalition Strategies

Authors: Nathalie Bertrand, Patricia Bouyer, and Anirban Majumdar

Published in: LIPIcs, Volume 182, 40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020)

Abstract
Concurrent games with a fixed number of agents have been thoroughly studied, with various solution concepts and objectives for the agents. In this paper, we consider concurrent games with an arbitrary number of agents, and study the problem of synthesizing a coalition strategy to achieve a global safety objective. The problem is non-trivial since the agents do not know a priori how many they are when they start the game. We prove that the existence of a safe arbitrary-large coalition strategy for safety objectives is a PSPACE-hard problem that can be decided in exponential space.
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Nathalie Bertrand, Patricia Bouyer, and Anirban Majumdar. Synthesizing Safe Coalition Strategies. In 40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 182, pp. 39:1-39:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{bertrand_et_al:LIPIcs.FSTTCS.2020.39,
  author =	{Bertrand, Nathalie and Bouyer, Patricia and Majumdar, Anirban},
  title =	{{Synthesizing Safe Coalition Strategies}},
  booktitle =	{40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020)},
  pages =	{39:1--39:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-174-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{182},
  editor =	{Saxena, Nitin and Simon, Sunil},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2020.39},
  URN =		{urn:nbn:de:0030-drops-132807},
  doi =		{10.4230/LIPIcs.FSTTCS.2020.39},
  annote =	{Keywords: concurrent games, parameterized verification, strategy synthesis}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2020.40
Dynamic Network Congestion Games

Authors: Nathalie Bertrand, Nicolas Markey, Suman Sadhukhan, and Ocan Sankur

Published in: LIPIcs, Volume 182, 40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020)

Abstract
Congestion games are a classical type of games studied in game theory, in which n players choose a resource, and their individual cost increases with the number of other players choosing the same resource. In network congestion games (NCGs), the resources correspond to simple paths in a graph, e.g. representing routing options from a source to a target. In this paper, we introduce a variant of NCGs, referred to as dynamic NCGs: in this setting, players take transitions synchronously, they select their next transitions dynamically, and they are charged a cost that depends on the number of players simultaneously using the same transition. We study, from a complexity perspective, standard concepts of game theory in dynamic NCGs: social optima, Nash equilibria, and subgame perfect equilibria. Our contributions are the following: the existence of a strategy profile with social cost bounded by a constant is in PSPACE and NP-hard. (Pure) Nash equilibria always exist in dynamic NCGs; the existence of a Nash equilibrium with bounded cost can be decided in EXPSPACE, and computing a witnessing strategy profile can be done in doubly-exponential time. The existence of a subgame perfect equilibrium with bounded cost can be decided in 2EXPSPACE, and a witnessing strategy profile can be computed in triply-exponential time.
Cite as

Nathalie Bertrand, Nicolas Markey, Suman Sadhukhan, and Ocan Sankur. Dynamic Network Congestion Games. In 40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 182, pp. 40:1-40:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{bertrand_et_al:LIPIcs.FSTTCS.2020.40,
  author =	{Bertrand, Nathalie and Markey, Nicolas and Sadhukhan, Suman and Sankur, Ocan},
  title =	{{Dynamic Network Congestion Games}},
  booktitle =	{40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020)},
  pages =	{40:1--40:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-174-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{182},
  editor =	{Saxena, Nitin and Simon, Sunil},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2020.40},
  URN =		{urn:nbn:de:0030-drops-132811},
  doi =		{10.4230/LIPIcs.FSTTCS.2020.40},
  annote =	{Keywords: Congestion games, Nash equilibria, Subgame perfect equilibria, Complexity}
}
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