15 Search Results for "Défago, Xavier"

Volume

LIPIcs, Volume 286

27th International Conference on Principles of Distributed Systems (OPODIS 2023)

OPODIS 2023, December 6-8, 2023, Tokyo, Japan

Editors: Alysson Bessani, Xavier Défago, Junya Nakamura, Koichi Wada, and Yukiko Yamauchi

Document
DOI: 10.4230/LIPIcs.OPODIS.2025.7
Mobile Byzantine Agreement in a Trusted World

Authors: Bo Pan and Maria Potop-Butucaru

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
In this paper, we address the Byzantine Agreement problem in synchronous systems where Byzantine agents can move from process to process, corrupting their host. We focus on two representative models: Garay’s and Buhrman’s models. In Garay’s model, when a process has been left by the Byzantine agent, it enters a cured state, is aware of its condition, and can remain silent for a round to prevent the dissemination of incorrect information. In Buhrman’s model, a Byzantine agent moves together with the message. It has been shown that solving Byzantine Agreement requires at least 4t + 1 processes in Garay’s model, and at least 3t + 1 in Buhrman’s model. In this paper, we aim to increase the tolerance to mobile Byzantine agents by integrating a trusted counter abstraction into both models. This abstraction prevents nodes from equivocating. In the new models, we prove that at least 3t+1, respectively 2t+1 processors are needed to tolerate t mobile Byzantine agents. Furthermore, we propose novel Mobile Byzantine Agreement algorithms that match these new lower bounds for both Garay’s and Buhrman’s models, achieving agreement in 𝒪(n) synchronous rounds.
Cite as

Bo Pan and Maria Potop-Butucaru. Mobile Byzantine Agreement in a Trusted World. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 7:1-7:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{pan_et_al:LIPIcs.OPODIS.2025.7,
  author =	{Pan, Bo and Potop-Butucaru, Maria},
  title =	{{Mobile Byzantine Agreement in a Trusted World}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{7:1--7:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.7},
  URN =		{urn:nbn:de:0030-drops-251809},
  doi =		{10.4230/LIPIcs.OPODIS.2025.7},
  annote =	{Keywords: Byzantine Agreement, Mobile Faults, Trusted Abstractions}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.9
Contention-Aware Cooperation

Authors: Timothé Albouy, Davide Frey, Mathieu Gestin, Michel Raynal, and François Taïani

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
As shown by Reliable Broadcast and Consensus, cooperation among a set of independent computing entities (sequential processes) is crucial in fault-tolerant distributed computing. Considering n-process asynchronous message-passing systems where some processes may be Byzantine, this paper introduces a novel cooperation abstraction, Contention-Aware Cooperation (CAC). While Reliable Broadcast is a one-to-n cooperation abstraction and Consensus is an n-to-n cooperation abstraction, CAC is a d-to-n cooperation abstraction where d (1 ≤ d ≤ n) varies with each run and remains unknown to the processes. Correct processes accept the same set of 𝓁 pairs ⟨ v,i ⟩ (v is the value proposed by p_i) from the d proposer processes, where 1 ≤ 𝓁 ≤ d and (as d) 𝓁 remains unknown to the processes (except in specific cases). Those 𝓁 values are accepted one at a time, potentially in different orders at each process. In addition, CAC provides each process with an imperfect oracle that provides insights into the values that they may accept in the future. Interestingly, the CAC abstraction is particularly efficient in favorable circumstances, when the oracle becomes accurate, which processes can detect. To illustrate its practical utility, the paper details two applications leveraging CAC: a fast consensus implementation optimized for low contention (named Cascading Consensus), and a novel naming problem that can be solved under full asynchrony. All algorithms presented require signatures.
Cite as

Timothé Albouy, Davide Frey, Mathieu Gestin, Michel Raynal, and François Taïani. Contention-Aware Cooperation. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 9:1-9:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{albouy_et_al:LIPIcs.OPODIS.2025.9,
  author =	{Albouy, Timoth\'{e} and Frey, Davide and Gestin, Mathieu and Raynal, Michel and Ta\"{i}ani, Fran\c{c}ois},
  title =	{{Contention-Aware Cooperation}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{9:1--9:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.9},
  URN =		{urn:nbn:de:0030-drops-251823},
  doi =		{10.4230/LIPIcs.OPODIS.2025.9},
  annote =	{Keywords: Agreement, Asynchronous message-passing system, Byzantine processes, Conflict detection, Consensus, Cooperation abstraction, Distributed computing, Fault tolerance, Optimistically terminating consensus, Short-naming}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.24
On Time-Optimal, Fault-Tolerant Algorithms for Connected Consensus Beyond Grade Two

Authors: Alan Ernesto Arteaga Vázquez

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
A common question in the asynchronous model is whether some given notion of agreement between processes is achievable. Usually, we formalise such agreement notions in the form of agreement problems. Some of these problems also receive the name of coordination primitives. Several fault-tolerant algorithms in asynchronous systems rely upon the use of different primitives as building blocks, such as adopt-commit, crusader agreement, or graded broadcast. Recently, the connected consensus problem - a form of agreement over a specific family of graphs parametrised by a positive integer R- was introduced. This problem unifies the three mentioned primitives while extending them for multi-valued inputs. Moreover, the problem is equipped with a security condition called binding, which limits the effect of malicious processes over the decision of correct parties. While fault-tolerant connected consensus algorithms for R = 1 and R = 2 are known, the existence of algorithmic solutions for any positive integer parameter remained an open question. In this work, we introduce a pair of fault-tolerant algorithms for connected consensus when the R parameter is any positive integer. We introduce a crash-resilient algorithm, which is optimal with respect to the maximum number of possible faulty processes. Our second algorithm is resilient to Byzantine failures; whose failure-resilience is optimal for a specific class of algorithms. Both algorithms satisfy the binding property and match the best known time complexities achieved for the R = 1 and R = 2 cases, further achieving time optimality for the general case in the crash-failure setting, and asymptotic time optimality in the Byzantine scenario.
Cite as

Alan Ernesto Arteaga Vázquez. On Time-Optimal, Fault-Tolerant Algorithms for Connected Consensus Beyond Grade Two. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 24:1-24:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{arteagavazquez:LIPIcs.OPODIS.2025.24,
  author =	{Arteaga V\'{a}zquez, Alan Ernesto},
  title =	{{On Time-Optimal, Fault-Tolerant Algorithms for Connected Consensus Beyond Grade Two}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{24:1--24:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.24},
  URN =		{urn:nbn:de:0030-drops-251973},
  doi =		{10.4230/LIPIcs.OPODIS.2025.24},
  annote =	{Keywords: Approximate Agreement, Binding, Connected Consensus}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2025.56
Brief Announcement: Universal Dancing by Luminous Robots Under Sequential Schedulers

Authors: Caterina Feletti, Paola Flocchini, Debasish Pattanayak, Giuseppe Prencipe, and Nicola Santoro

Published in: LIPIcs, Volume 356, 39th International Symposium on Distributed Computing (DISC 2025)

Abstract
The Dancing problem requires a swarm of n autonomous mobile robots to form a sequence of patterns, aka perform a choreography. Existing work has proven that some crucial restrictions on choreographies and initial configurations (e.g., on repetitions of patterns, periodicity, symmetries, contractions/expansions) must hold so that the Dancing problem can be solved under certain robot models. Here, we prove that these necessary constraints can be dropped by considering the LUMI model (i.e., where robots are endowed with a light whose color can be chosen from a constant-size palette) under the quite unexplored sequential scheduler. We formalize the class of Universal Dancing problems which require a swarm of n robots starting from any initial configuration to perform a (periodic or finite) sequence of arbitrary patterns, only provided that each pattern consists of n vertices (including multiplicities). However, we prove that, to be solvable under LUMI, the length of the feasible choreographies is bounded by the compositions of n into the number of colors available to the robots. We provide an algorithm solving the Universal Dancing problem by exploiting the peculiar capability of sequential robots to implement a distributed counter mechanism. Even assuming non-rigid movements, our algorithm ensures spatial homogeneity of the performed choreography.
Cite as

Caterina Feletti, Paola Flocchini, Debasish Pattanayak, Giuseppe Prencipe, and Nicola Santoro. Brief Announcement: Universal Dancing by Luminous Robots Under Sequential Schedulers. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 56:1-56:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{feletti_et_al:LIPIcs.DISC.2025.56,
  author =	{Feletti, Caterina and Flocchini, Paola and Pattanayak, Debasish and Prencipe, Giuseppe and Santoro, Nicola},
  title =	{{Brief Announcement: Universal Dancing by Luminous Robots Under Sequential Schedulers}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{56:1--56:7},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-402-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{356},
  editor =	{Kowalski, Dariusz R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2025.56},
  URN =		{urn:nbn:de:0030-drops-248724},
  doi =		{10.4230/LIPIcs.DISC.2025.56},
  annote =	{Keywords: Luminous Robots, Sequence of Patterns, Pattern Formation, Sequential Scheduler}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2025.57
Brief Announcement: The Virtue of Self-Consistency

Authors: Fabian Frei and Koichi Wada

Published in: LIPIcs, Volume 356, 39th International Symposium on Distributed Computing (DISC 2025)

Abstract
We show that self-consistency can be a crucial property for autonomous mobile robots. Specifically, we consider the task of gathering three robots, placed adversarially in distinct locations in the Euclidean plane, in a single point. We assume the natural scheduler RoundRobin, which activates the robots in turns. An activated robot perceives all robot locations in an adversarially scaled, rotated, and mirrored Cartesian coordinate system with itself at the origin and then moves wherever it wants. We show that this task cannot be solved in the default robot model (without any consistency guarantees and no multiplicity detection) but becomes feasible if we assume self-consistency (i.e., no changes between the different activations of the same robot) of either the unit length (i.e., no scaling) or the compass (i.e., no rotating) by providing explicit algorithms.
Cite as

Fabian Frei and Koichi Wada. Brief Announcement: The Virtue of Self-Consistency. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 57:1-57:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{frei_et_al:LIPIcs.DISC.2025.57,
  author =	{Frei, Fabian and Wada, Koichi},
  title =	{{Brief Announcement: The Virtue of Self-Consistency}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{57:1--57:7},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-402-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{356},
  editor =	{Kowalski, Dariusz R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2025.57},
  URN =		{urn:nbn:de:0030-drops-248737},
  doi =		{10.4230/LIPIcs.DISC.2025.57},
  annote =	{Keywords: Autonomous Mobile Robots, Distinct Gathering, Round Robin, Disorientation, Self-Consistency}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2025.4
Ensuring Convergence and Invariants Without Coordination

Authors: Dina Borrego, Nuno Preguiça, Elisa Gonzalez Boix, and Carla Ferreira

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)

Abstract
The CAP theorem demonstrates a trade-off between consistency and availability (and, by extension, latency) in systems where network partitions are unavoidable, such as in cloud computing and local-first software. While adopting weak consistency can preserve availability, it may result in inconsistencies that compromise application correctness. Replicated data types provide a principled, coordination-free approach to guarantee convergence but do not consider application invariants. Existing methods for maintaining invariants in replicated systems either rely on coordination - undermining the benefits of weak consistency - or suffer from limited applicability. This paper introduces the No-Op framework, a generic approach for enforcing consistency without coordination while guaranteeing both convergence and invariant preservation. The core idea of the No-Op approach is to resolve conflicts among concurrent operations by prioritising one operation over the other according to programmer-defined conflict resolution policies. This prioritisation transforms the less-preferred operation into a no-side-effect operation, ensuring conflict-free execution. We formalise the model underlying the No-Op framework and introduce a replication protocol built upon it, accompanied by a formal proof of correctness for both the framework and the protocol. Furthermore, we demonstrate the framework’s applicability by showcasing the design of widely used replicated data types and the preservation of a wide range of application invariants.
Cite as

Dina Borrego, Nuno Preguiça, Elisa Gonzalez Boix, and Carla Ferreira. Ensuring Convergence and Invariants Without Coordination. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 4:1-4:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{borrego_et_al:LIPIcs.ECOOP.2025.4,
  author =	{Borrego, Dina and Pregui\c{c}a, Nuno and Gonzalez Boix, Elisa and Ferreira, Carla},
  title =	{{Ensuring Convergence and Invariants Without Coordination}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{4:1--4:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan 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.ECOOP.2025.4},
  URN =		{urn:nbn:de:0030-drops-232978},
  doi =		{10.4230/LIPIcs.ECOOP.2025.4},
  annote =	{Keywords: distributed systems, conflict resolution, RDTs, invariant preservation}
}
Document
DOI: 10.4230/LIPIcs.SAND.2025.10
Fault Detection and Identification by Autonomous Mobile Robots

Authors: Stefano Clemente and Caterina Feletti

Published in: LIPIcs, Volume 330, 4th Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2025)

Abstract
The Look-Compute-Move model (LCM) is adopted to study swarms of mobile robots that have to solve a given problem. Robots are generally assumed to be autonomous, indistinguishable, anonymous, homogeneous and to move on the Euclidean plane. Different LCM sub-models have been theorized to study different settings and their computational power. Notably, the literature has focused on four base models (i.e., OBLOT, FSTA, FCOM, LUMI) that differ in memory and communication capabilities, and in different synchronization modes (e.g., fully synchronous FSYNCH, semi-synchronous SSYNCH). In this paper, we consider fault-prone models where robots can suffer from crash faults: each robot may irremediably stop working after an unpredictable time. We study the general Fault Detection (FD) problem which is solved by a swarm if it correctly detects whether a faulty robot exists in the swarm. The Fault Identification (FI) problem additionally requires identifying which robots are faulty. We consider 12 LCM sub-models (OBLOT, FSTA, FCOM, LUMI, combined with FSYNCH, SSYNCH, and the round-robin RROBIN) and we study the (im)possibility of designing reliable procedures to solve FD or FI. In particular, we propose three distributed algorithms so that a swarm can collectively solve FD under the models LUMI^FSYNCH, FCOM^FSYNCH, and LUMI^RROBIN.
Cite as

Stefano Clemente and Caterina Feletti. Fault Detection and Identification by Autonomous Mobile Robots. In 4th Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 330, pp. 10:1-10:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{clemente_et_al:LIPIcs.SAND.2025.10,
  author =	{Clemente, Stefano and Feletti, Caterina},
  title =	{{Fault Detection and Identification by Autonomous Mobile Robots}},
  booktitle =	{4th Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2025)},
  pages =	{10:1--10:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-368-3},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{330},
  editor =	{Meeks, Kitty and Scheideler, Christian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SAND.2025.10},
  URN =		{urn:nbn:de:0030-drops-230639},
  doi =		{10.4230/LIPIcs.SAND.2025.10},
  annote =	{Keywords: Autonomous mobile robots, Faulty robots, Look-Compute-Move, Fault detection, Fault identification, Round-robin}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.12
Crash-Tolerant Perpetual Exploration with Myopic Luminous Robots on Rings

Authors: Fukuhito Ooshita, Naoki Kitamura, Ryota Eguchi, Michiko Inoue, Hirotsugu Kakugawa, Sayaka Kamei, Masahiro Shibata, and Yuichi Sudo

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
We investigate crash-tolerant perpetual exploration algorithms by myopic luminous robots on ring networks. Myopic robots mean that they can observe nodes only within a certain fixed distance ϕ, and luminous robots mean that they have light devices that can emit a color from a set of colors. The goal of perpetual exploration is to ensure that robots, starting from specific initial positions and colors, move in such a way that every node is visited by at least one robot infinitely often. As a main contribution, we clarify the tight necessary and sufficient number of robots to realize perpetual exploration when at most f robots crash. In the fully synchronous model, we prove that f+2 robots are necessary and sufficient for any ϕ ≥ 1. In the semi-synchronous and asynchronous models, we prove that 3f+3 (resp., 2f+2) robots are necessary and sufficient if ϕ = 1 (resp., ϕ ≥ 2).
Cite as

Fukuhito Ooshita, Naoki Kitamura, Ryota Eguchi, Michiko Inoue, Hirotsugu Kakugawa, Sayaka Kamei, Masahiro Shibata, and Yuichi Sudo. Crash-Tolerant Perpetual Exploration with Myopic Luminous Robots on Rings. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 12:1-12:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ooshita_et_al:LIPIcs.OPODIS.2024.12,
  author =	{Ooshita, Fukuhito and Kitamura, Naoki and Eguchi, Ryota and Inoue, Michiko and Kakugawa, Hirotsugu and Kamei, Sayaka and Shibata, Masahiro and Sudo, Yuichi},
  title =	{{Crash-Tolerant Perpetual Exploration with Myopic Luminous Robots on Rings}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{12:1--12:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.12},
  URN =		{urn:nbn:de:0030-drops-225486},
  doi =		{10.4230/LIPIcs.OPODIS.2024.12},
  annote =	{Keywords: mobile robots, crash faults, LCM model, exploration}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.OPODIS.2023
LIPIcs, Volume 286, OPODIS 2023, Complete Volume

Authors: Alysson Bessani, Xavier Défago, Junya Nakamura, Koichi Wada, and Yukiko Yamauchi

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

Abstract
LIPIcs, Volume 286, OPODIS 2023, Complete Volume
Cite as

27th International Conference on Principles of Distributed Systems (OPODIS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 286, pp. 1-702, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Proceedings{bessani_et_al:LIPIcs.OPODIS.2023,
  title =	{{LIPIcs, Volume 286, OPODIS 2023, Complete Volume}},
  booktitle =	{27th International Conference on Principles of Distributed Systems (OPODIS 2023)},
  pages =	{1--702},
  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},
  URN =		{urn:nbn:de:0030-drops-194896},
  doi =		{10.4230/LIPIcs.OPODIS.2023},
  annote =	{Keywords: LIPIcs, Volume 286, OPODIS 2023, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.OPODIS.2023.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Alysson Bessani, Xavier Défago, Junya Nakamura, Koichi Wada, and Yukiko Yamauchi

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

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

27th International Conference on Principles of Distributed Systems (OPODIS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 286, pp. 0:i-0:xvi, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bessani_et_al:LIPIcs.OPODIS.2023.0,
  author =	{Bessani, Alysson and D\'{e}fago, Xavier and Nakamura, Junya and Wada, Koichi and Yamauchi, Yukiko},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{27th International Conference on Principles of Distributed Systems (OPODIS 2023)},
  pages =	{0:i--0:xvi},
  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.2023.0},
  URN =		{urn:nbn:de:0030-drops-194903},
  doi =		{10.4230/LIPIcs.OPODIS.2023.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
DOI: 10.4230/LITES.8.2.2
Swarms of Mobile Robots: Towards Versatility with Safety

Authors: Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain

Published in: LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2

Abstract
We present Pactole, a formal framework to design and prove the correctness of protocols (or the impossibility of their existence) that target mobile robotic swarms. Unlike previous approaches, our methodology unifies in a single formalism the execution model, the problem specification, the protocol, and its proof of correctness. The Pactole framework makes use of the Coq proof assistant, and is specially targeted at protocol designers and problem specifiers, so that a common unambiguous language is used from the very early stages of protocol development. We stress the underlying framework design principles to enable high expressivity and modularity, and provide concrete examples about how the Pactole framework can be used to tackle actual problems, some previously addressed by the Distributed Computing community, but also new problems, while being certified correct.
Cite as

Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain. Swarms of Mobile Robots: Towards Versatility with Safety. In LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2, pp. 02:1-02:36, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Article{courtieu_et_al:LITES.8.2.2,
  author =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  title =	{{Swarms of Mobile Robots: Towards Versatility with Safety}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{02:1--02:36},
  ISSN =	{2199-2002},
  year =	{2022},
  volume =	{8},
  number =	{2},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.8.2.2},
  URN =		{urn:nbn:de:0030-drops-192942},
  doi =		{10.4230/LITES.8.2.2},
  annote =	{Keywords: distributed algorithm, mobile autonomous robots, formal proof}
}
Document
DOI: 10.4230/LIPIcs.DISC.2020.11
Communication Efficient Self-Stabilizing Leader Election

Authors: Xavier Défago, Yuval Emek, Shay Kutten, Toshimitsu Masuzawa, and Yasumasa Tamura

Published in: LIPIcs, Volume 179, 34th International Symposium on Distributed Computing (DISC 2020)

Abstract
This paper presents a randomized self-stabilizing algorithm that elects a leader r in a general n-node undirected graph and constructs a spanning tree T rooted at r. The algorithm works under the synchronous message passing network model, assuming that the nodes know a linear upper bound on n and that each edge has a unique ID known to both its endpoints (or, alternatively, assuming the KT₁ model). The highlight of this algorithm is its superior communication efficiency: It is guaranteed to send a total of Õ (n) messages, each of constant size, till stabilization, while stabilizing in Õ (n) rounds, in expectation and with high probability. After stabilization, the algorithm sends at most one constant size message per round while communicating only over the (n - 1) edges of T. In all these aspects, the communication overhead of the new algorithm is far smaller than that of the existing (mostly deterministic) self-stabilizing leader election algorithms. The algorithm is relatively simple and relies mostly on known modules that are common in the fault free leader election literature; these modules are enhanced in various subtle ways in order to assemble them into a communication efficient self-stabilizing algorithm.
Cite as

Xavier Défago, Yuval Emek, Shay Kutten, Toshimitsu Masuzawa, and Yasumasa Tamura. Communication Efficient Self-Stabilizing Leader Election. In 34th International Symposium on Distributed Computing (DISC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 179, pp. 11:1-11:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{defago_et_al:LIPIcs.DISC.2020.11,
  author =	{D\'{e}fago, Xavier and Emek, Yuval and Kutten, Shay and Masuzawa, Toshimitsu and Tamura, Yasumasa},
  title =	{{Communication Efficient Self-Stabilizing Leader Election}},
  booktitle =	{34th International Symposium on Distributed Computing (DISC 2020)},
  pages =	{11:1--11:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-168-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{179},
  editor =	{Attiya, Hagit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2020.11},
  URN =		{urn:nbn:de:0030-drops-130892},
  doi =		{10.4230/LIPIcs.DISC.2020.11},
  annote =	{Keywords: self-stabilization, leader election, communication overhead}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2019.41
Brief Announcement: Model Checking Rendezvous Algorithms for Robots with Lights in Euclidean Space

Authors: Xavier Défago, Adam Heriban, Sébastien Tixeuil, and Koichi Wada

Published in: LIPIcs, Volume 146, 33rd International Symposium on Distributed Computing (DISC 2019)

Abstract
This announces the first successful attempt at using model-checking techniques to verify the correctness of self-stabilizing distributed algorithms for robots evolving in a continuous environment. The study focuses on the problem of rendezvous of two robots with lights and presents a generic verification model for the SPIN model checker. It will be presented in full at an upcoming venue.
Cite as

Xavier Défago, Adam Heriban, Sébastien Tixeuil, and Koichi Wada. Brief Announcement: Model Checking Rendezvous Algorithms for Robots with Lights in Euclidean Space. In 33rd International Symposium on Distributed Computing (DISC 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 146, pp. 41:1-41:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{defago_et_al:LIPIcs.DISC.2019.41,
  author =	{D\'{e}fago, Xavier and Heriban, Adam and Tixeuil, S\'{e}bastien and Wada, Koichi},
  title =	{{Brief Announcement: Model Checking Rendezvous Algorithms for Robots with Lights in Euclidean Space}},
  booktitle =	{33rd International Symposium on Distributed Computing (DISC 2019)},
  pages =	{41:1--41:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-126-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{146},
  editor =	{Suomela, Jukka},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2019.41},
  URN =		{urn:nbn:de:0030-drops-113487},
  doi =		{10.4230/LIPIcs.DISC.2019.41},
  annote =	{Keywords: Autonomous mobile robots, Rendezvous, Lights, Model Checking}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2018.24
Optimal Rendezvous L-Algorithms for Asynchronous Mobile Robots with External-Lights

Authors: Takashi Okumura, Koichi Wada, and Xavier Défago

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
We study the Rendezvous problem for two autonomous mobile robots in asynchronous settings with persistent memory called light. It is well known that Rendezvous is impossible in a basic model when robots have no lights, even if the system is semi-synchronous. On the other hand, Rendezvous is possible if robots have lights of various types with a constant number of colors. If robots can observe not only their own lights but also other robots' lights, their lights are called full-light. If robots can only observe the state of other robots' lights, the lights are called external-light. This paper focuses on robots with external-lights in asynchronous settings and a particular class of algorithms called L-algorithms, where an L-algorithm computes a destination based only on the current colors of observable lights. When considering L-algorithms, Rendezvous can be solved by robots with full-lights and three colors in general asynchronous settings (called ASYNC) and the number of colors is optimal under these assumptions. In contrast, there exist no L-algorithms in ASYNC with external-lights regardless of the number of colors. In this paper, extending the impossibility result, we show that there exist no L-algorithms in so-called LC-1-Bounded ASYNC with external-lights regardless of the number of colors, where LC-1-Bounded ASYNC is a proper subset of ASYNC and other robots can execute at most one Look operation between the Look operation of a robot and its subsequent Compute operation. We also show that LC-1-Bounded ASYNC is the minimal subclass in which no L-algorithms with external-lights exist. That is, Rendezvous can be solved by L-algorithms using external-lights with a finite number of colors in LC-0-Bounded ASYNC (equivalently LC-atomic ASYNC). Furthermore, we show that the algorithms are optimal in the number of colors they use.
Cite as

Takashi Okumura, Koichi Wada, and Xavier Défago. Optimal Rendezvous L-Algorithms for Asynchronous Mobile Robots with External-Lights. In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, pp. 24:1-24:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{okumura_et_al:LIPIcs.OPODIS.2018.24,
  author =	{Okumura, Takashi and Wada, Koichi and D\'{e}fago, Xavier},
  title =	{{Optimal Rendezvous L-Algorithms for Asynchronous Mobile Robots with External-Lights}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  pages =	{24:1--24:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018.24},
  URN =		{urn:nbn:de:0030-drops-100843},
  doi =		{10.4230/LIPIcs.OPODIS.2018.24},
  annote =	{Keywords: Autonomous mobile robots, Rendezvous, Lights, L-algorithms}
}
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