29 Search Results for "Diekert, Volker"

Document
DOI: 10.4230/LIPIcs.SWAT.2026.12
Strategy Repair in Reachability Games via a Graph Quotientation

Authors: Tiziana Calamoneri, Pierre Gaillard, Giacomo Paesani, and Giuseppe Perelli

Published in: LIPIcs, Volume 370, 20th Scandinavian Symposium on Algorithm Theory (SWAT 2026)

Abstract
Reachability Games over graphs (RGs) are a powerful modelling tool for synthesis and planning. The solutions to RGs are strategies that are used in program design. Sometimes, due to model deviation at execution time, specification updates, or simply a bug, the strategy provided as a solution to an RG no longer works. Strategy Repair aims to solve this problem by adjusting strategies with a minimum number of modifications. Such a minimisation requirement is motivated by the costs that one may incur when implementing the new strategy. To minimise implementation costs, one wants to reuse as much of the provided strategy as possible. In the literature, Strategy Repair has been investigated from both theoretical and practical perspectives. First, it has been shown to be NP-complete. Second, two algorithmic approaches have been proposed to tackle the problem in practice, one provides an optimal solution, the other an approximated solution. Both approaches underutilise the graph-theoretical properties of games, which could significantly improve their performance and accuracy (in the case of approximation algorithms). This paper provides a graph-theoretic characterisation of Strategy Repair that provably improves every algorithmic approach to solving the problem. It does so by introducing a new notion of quotient graph that allows us to identify and merge those vertices that are equivalent from the perspective of every solution to the problem. This way, solving Strategy Repair can be done in a reduced instance, which we call the quotient game. The approach not only reduces the problem’s input size, but also improves the effectiveness of MustFix, an optimisation condition previously introduced for the problem. Besides the theoretical characterisation, we test our approach empirically by running experiments to demonstrate improvements over the quotient graph approach.
Cite as

Tiziana Calamoneri, Pierre Gaillard, Giacomo Paesani, and Giuseppe Perelli. Strategy Repair in Reachability Games via a Graph Quotientation. In 20th Scandinavian Symposium on Algorithm Theory (SWAT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 370, pp. 12:1-12:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{calamoneri_et_al:LIPIcs.SWAT.2026.12,
  author =	{Calamoneri, Tiziana and Gaillard, Pierre and Paesani, Giacomo and Perelli, Giuseppe},
  title =	{{Strategy Repair in Reachability Games via a Graph Quotientation}},
  booktitle =	{20th Scandinavian Symposium on Algorithm Theory (SWAT 2026)},
  pages =	{12:1--12:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-421-5},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{370},
  editor =	{Fraigniaud, Pierre},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SWAT.2026.12},
  URN =		{urn:nbn:de:0030-drops-260481},
  doi =		{10.4230/LIPIcs.SWAT.2026.12},
  annote =	{Keywords: Reachability Games, Strategy Repair, Strategic Reasoning, Automated Reasoning}
}
Document
DOI: 10.4230/LIPIcs.CPM.2026.24
On Occurrence-Preserving Morphisms

Authors: Kaisei Kishi, Peaker Guo, Cristian Urbina, and Hideo Bannai

Published in: LIPIcs, Volume 369, 37th Annual Symposium on Combinatorial Pattern Matching (CPM 2026)

Abstract
A morphism is a mapping that transforms words through letter-wise substitution, where each symbol is consistently replaced by a fixed word. In the field of combinatorics on words, one topic that has attracted considerable attention is the characterization of morphisms that preserve specific properties, such as overlap-freeness, square-freeness, lexicographic order, and primitivity. Continuing this direction, we initiate the study on occurrence-preserving morphisms, which address the following fundamental question: given a morphism ϕ, two words u and v, and k ≥ 1, under what conditions does the number of occurrences of u in v equal the number of occurrences of ϕ^k(u) in ϕ^k(v)? To answer this question, we introduce the notion of interference-free morphisms, examine their properties, and uncover a connection to recognizable morphisms. We then present a precise characterization of occurrence-preserving morphisms in terms of interference-freeness. As applications of our characterization, we first show that there exists a bijection between the starting positions of the occurrences of u in v and those of ϕ^k(u) in ϕ^k(v). We then apply the characterization to the Fibonacci and Thue-Morse words to identify their minimal unique substrings (MUSs). Finally, we exploit the connection between MUSs and net occurrences to simplify existing proofs on net occurrences in these words.
Cite as

Kaisei Kishi, Peaker Guo, Cristian Urbina, and Hideo Bannai. On Occurrence-Preserving Morphisms. In 37th Annual Symposium on Combinatorial Pattern Matching (CPM 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 369, pp. 24:1-24:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{kishi_et_al:LIPIcs.CPM.2026.24,
  author =	{Kishi, Kaisei and Guo, Peaker and Urbina, Cristian and Bannai, Hideo},
  title =	{{On Occurrence-Preserving Morphisms}},
  booktitle =	{37th Annual Symposium on Combinatorial Pattern Matching (CPM 2026)},
  pages =	{24:1--24:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-420-8},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{369},
  editor =	{Bille, Philip and Prezza, Nicola},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CPM.2026.24},
  URN =		{urn:nbn:de:0030-drops-259504},
  doi =		{10.4230/LIPIcs.CPM.2026.24},
  annote =	{Keywords: Property-preserving morphisms, interference-free morphisms, recognizable morphisms, injective morphisms, Fibonacci words, Thue-Morse words, minimal unique substrings (MUSs), net occurrences}
}
Document
DOI: 10.4230/LIPIcs.STACS.2026.64
One-Clock Synthesis Problems

Authors: Sławomir Lasota, Mathieu Lehaut, Julie Parreaux, and Radosław Piórkowski

Published in: LIPIcs, Volume 364, 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)

Abstract
We study a generalisation of Büchi-Landweber games to the timed setting. The winning condition is specified by a non-deterministic timed automaton, and one of the players can elapse time. We perform a systematic study of synthesis problems in all variants of timed games, depending on which player’s winning condition is specified, and which player’s strategy (or controller, a finite-memory strategy) is sought. As our main result we prove ubiquitous undecidability in all the variants, both for strategy and controller synthesis, already for winning conditions specified by one-clock automata. This strengthens and generalises previously known undecidability results. We also fully characterise those cases where finite memory is sufficient to win, namely existence of a strategy implies existence of a controller. All our results are stated in the timed setting, while analogous results hold in the data setting where one-clock automata are replaced by one-register ones.
Cite as

Sławomir Lasota, Mathieu Lehaut, Julie Parreaux, and Radosław Piórkowski. One-Clock Synthesis Problems. In 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 364, pp. 64:1-64:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{lasota_et_al:LIPIcs.STACS.2026.64,
  author =	{Lasota, S{\l}awomir and Lehaut, Mathieu and Parreaux, Julie and Pi\'{o}rkowski, Rados{\l}aw},
  title =	{{One-Clock Synthesis Problems}},
  booktitle =	{43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)},
  pages =	{64:1--64:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-412-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{364},
  editor =	{Mahajan, Meena and Manea, Florin and McIver, Annabelle and Thắng, Nguy\~{ê}n Kim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2026.64},
  URN =		{urn:nbn:de:0030-drops-255533},
  doi =		{10.4230/LIPIcs.STACS.2026.64},
  annote =	{Keywords: timed automata, register automata, B\"{u}chi-Landweber games, Church synthesis problem, reactive synthesis problem}
}
Document
DOI: 10.4230/LIPIcs.STACS.2026.60
The Asymptotic Size of Finite Irreducible Semigroups of Rational Matrices

Authors: Stefan Kiefer and Andrew Ryzhikov

Published in: LIPIcs, Volume 364, 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)

Abstract
We study finite semigroups of n × n matrices with rational entries. Such semigroups provide a rich generalization of transition monoids of unambiguous (and, in particular, deterministic) finite automata. In this paper we determine the maximum size of finite semigroups of rational n × n matrices, with the goal of shedding more light on the structure of such matrix semigroups. While in general such semigroups can be arbitrarily large in terms of n, a classical result of Schützenberger from 1962 implies an upper bound of 2^{𝒪(n² log n)} for irreducible semigroups, i.e., the only subspaces of ℚⁿ that are invariant for all matrices in the semigroup are ℚⁿ and the subspace consisting only of the zero vector. Irreducible matrix semigroups can be viewed as the building blocks of general matrix semigroups, and as such play an important role in mathematics and computer science. From the point of view of automata theory, they generalize strongly connected automata. Using a very different technique from that of Schützenberger, we improve the upper bound on the cardinality to 3^{n²}. This is the main result of the paper. The bound is in some sense tight, as we show that there exists, for every n, a finite irreducible semigroup with 3^{⌊ n²/4 ⌋} rational matrices. Our main result also leads to an improvement of a bound, due to Almeida and Steinberg, on the mortality threshold. The mortality threshold is a number 𝓁 such that if the zero matrix is in the semigroup, then the zero matrix can be written as a product of at most 𝓁 matrices from any subset that generates the semigroup.
Cite as

Stefan Kiefer and Andrew Ryzhikov. The Asymptotic Size of Finite Irreducible Semigroups of Rational Matrices. In 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 364, pp. 60:1-60:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{kiefer_et_al:LIPIcs.STACS.2026.60,
  author =	{Kiefer, Stefan and Ryzhikov, Andrew},
  title =	{{The Asymptotic Size of Finite Irreducible Semigroups of Rational Matrices}},
  booktitle =	{43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)},
  pages =	{60:1--60:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-412-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{364},
  editor =	{Mahajan, Meena and Manea, Florin and McIver, Annabelle and Thắng, Nguy\~{ê}n Kim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2026.60},
  URN =		{urn:nbn:de:0030-drops-255496},
  doi =		{10.4230/LIPIcs.STACS.2026.60},
  annote =	{Keywords: finite matrix semigroups, irreducible matrix semigroups, matrix mortality, aperiodic semigroups, unambiguous automata, transition monoids}
}
Document
DOI: 10.4230/LIPIcs.STACS.2026.9
Algebraic Characterizations of Classes of Regular Languages in DynFO

Authors: Corentin Barloy, Felix Tschirbs, Nils Vortmeier, and Thomas Zeume

Published in: LIPIcs, Volume 364, 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)

Abstract
This paper explores the fine-grained structure of classes of regular languages maintainable in fragments of first-order logic within the dynamic descriptive complexity framework of Patnaik and Immerman. A result by Hesse states that the class of regular languages is maintainable by first-order formulas even if only unary auxiliary relations can be used. Another result by Gelade, Marquardt, and Schwentick states that the class of regular languages coincides with the class of languages maintainable by quantifier-free formulas with binary auxiliary relations. We refine Hesse’s result and show that with unary auxiliary data ∃^*∀^*-formulas can maintain all regular languages. We then obtain precise algebraic characterizations of the classes of languages maintainable with quantifier-free formulas and positive ∃^*-formulas in the presence of unary auxiliary relations.
Cite as

Corentin Barloy, Felix Tschirbs, Nils Vortmeier, and Thomas Zeume. Algebraic Characterizations of Classes of Regular Languages in DynFO. In 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 364, pp. 9:1-9:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{barloy_et_al:LIPIcs.STACS.2026.9,
  author =	{Barloy, Corentin and Tschirbs, Felix and Vortmeier, Nils and Zeume, Thomas},
  title =	{{Algebraic Characterizations of Classes of Regular Languages in DynFO}},
  booktitle =	{43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)},
  pages =	{9:1--9:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-412-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{364},
  editor =	{Mahajan, Meena and Manea, Florin and McIver, Annabelle and Thắng, Nguy\~{ê}n Kim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2026.9},
  URN =		{urn:nbn:de:0030-drops-254986},
  doi =		{10.4230/LIPIcs.STACS.2026.9},
  annote =	{Keywords: Dynamic descriptive complexity, formal languages, monoid theory}
}
Document
DOI: 10.4230/LIPIcs.STACS.2026.77
An Improved Version of Hmelevskii’s Theorem on Three-Variable Word Equations

Authors: Aleksi Saarela

Published in: LIPIcs, Volume 364, 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)

Abstract
Hmelevskii proved in 1971 that every constant-free three-variable word equation has a parametric solution. We prove an improved version of this result by showing that every such equation has a parametric solution using only three numerical parameters and with only two levels of nesting. This means that the structure of the solution sets of these equations is considerably simpler than has been known before.
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Aleksi Saarela. An Improved Version of Hmelevskii’s Theorem on Three-Variable Word Equations. In 43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 364, pp. 77:1-77:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{saarela:LIPIcs.STACS.2026.77,
  author =	{Saarela, Aleksi},
  title =	{{An Improved Version of Hmelevskii’s Theorem on Three-Variable Word Equations}},
  booktitle =	{43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)},
  pages =	{77:1--77:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-412-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{364},
  editor =	{Mahajan, Meena and Manea, Florin and McIver, Annabelle and Thắng, Nguy\~{ê}n Kim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2026.77},
  URN =		{urn:nbn:de:0030-drops-255664},
  doi =		{10.4230/LIPIcs.STACS.2026.77},
  annote =	{Keywords: Combinatorics on words, word equation, parametric word}
}
Document
DOI: 10.4230/LIPIcs.CSL.2026.43
Kamp Theorem for Pomset Languages of Higher Dimensional Automata

Authors: Emily Clement, Enzo Erlich, and Jérémy Ledent

Published in: LIPIcs, Volume 363, 34th EACSL Annual Conference on Computer Science Logic (CSL 2026)

Abstract
Temporal logics are a powerful tool to specify properties of computational systems. For concurrent programs, Higher Dimensional Automata (HDA) are a very expressive model of non-interleaving concurrency. HDA recognize languages of partially ordered multisets, or pomsets. Recent work has shown that Monadic Second Order (MSO) logic is as expressive as HDA for pomset languages. In the case of words, Kamp’s theorem states that First Order (FO) logic is as expressive as Linear Temporal Logic (LTL). In this paper, we extend this result to pomsets. To do so, we first investigate the class of pomset languages that are definable in FO. As expected, this is a strict subclass of MSO-definable languages. Then, we define a Linear Temporal Logic for pomsets (LTL_Poms), and show that it is equivalent to FO.
Cite as

Emily Clement, Enzo Erlich, and Jérémy Ledent. Kamp Theorem for Pomset Languages of Higher Dimensional Automata. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 43:1-43:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{clement_et_al:LIPIcs.CSL.2026.43,
  author =	{Clement, Emily and Erlich, Enzo and Ledent, J\'{e}r\'{e}my},
  title =	{{Kamp Theorem for Pomset Languages of Higher Dimensional Automata}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{43:1--43:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-411-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{363},
  editor =	{Guerrini, Stefano and K\"{o}nig, Barbara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.43},
  URN =		{urn:nbn:de:0030-drops-254685},
  doi =		{10.4230/LIPIcs.CSL.2026.43},
  annote =	{Keywords: Higher dimensional automata, temporal logic, Kamp’s theorem}
}
Document
DOI: 10.4230/LIPIcs.CSL.2026.28
Resourceful Traces for Commuting Processes

Authors: Matthew Earnshaw, Chad Nester, and Mario Román

Published in: LIPIcs, Volume 363, 34th EACSL Annual Conference on Computer Science Logic (CSL 2026)

Abstract
We show that, when the actions of a Mazurkiewicz trace are considered not merely as atomic but as transformations from a specified type of inputs to a specified type of outputs, we obtain a novel notion of presentation for effectful categories (also known as generalized Freyd categories), a well-known algebraic structure in the semantics of side-effecting computation. Like the usual representation of traces as graphs, our notion of presentation gives rise to a graphical representation of morphisms in effectful categories. We use our presentations to give a construction of the commuting tensor product of free effectful categories, capturing the combination of systems in which the actions of each must commute with one another, while still permitting exchange of resources.
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Matthew Earnshaw, Chad Nester, and Mario Román. Resourceful Traces for Commuting Processes. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 28:1-28:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{earnshaw_et_al:LIPIcs.CSL.2026.28,
  author =	{Earnshaw, Matthew and Nester, Chad and Rom\'{a}n, Mario},
  title =	{{Resourceful Traces for Commuting Processes}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{28:1--28:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-411-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{363},
  editor =	{Guerrini, Stefano and K\"{o}nig, Barbara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.28},
  URN =		{urn:nbn:de:0030-drops-254522},
  doi =		{10.4230/LIPIcs.CSL.2026.28},
  annote =	{Keywords: Mazurkiewicz traces, premonoidal categories, monoidal categories, effectful categories}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2026.7
An Unholy Trinity: TFNP, Polynomial Systems, and the Quantum Satisfiability Problem

Authors: Marco Aldi, Sevag Gharibian, and Dorian Rudolph

Published in: LIPIcs, Volume 362, 17th Innovations in Theoretical Computer Science Conference (ITCS 2026)

Abstract
The theory of Total Function NP (TFNP) and its subclasses says that, even if one is promised an efficiently verifiable proof exists for a problem, finding this proof can be intractable. Despite the success of the theory at showing intractability of problems such as computing Brouwer fixed points and Nash equilibria, subclasses of TFNP remain arguably few and far between. In this work, we define two new subclasses of TFNP borne of the study of complex polynomial systems: Multi-homogeneous Systems (MHS) and Sparse Fundamental Theorem of Algebra (SFTA). The first of these is based on Bézout’s theorem from algebraic geometry, marking the first TFNP subclass based on an algebraic geometric principle. At the heart of our study is the computational problem known as Quantum SAT (QSAT) with a System of Distinct Representatives (SDR), first studied by [Laumann, Läuchli, Moessner, Scardicchio, and Sondhi 2010]. Among other results, we show that QSAT with SDR is MHS-complete, thus giving not only the first link between quantum complexity theory and TFNP, but also the first TFNP problem whose classical variant (SAT with SDR) is easy but whose quantum variant is hard. We also show how to embed the roots of a sparse, high-degree, univariate polynomial into QSAT with SDR, obtaining that SFTA is contained in a zero-error version of MHS. We conjecture this construction also works in the low-error setting, which would imply SFTA ⊆ MHS.
Cite as

Marco Aldi, Sevag Gharibian, and Dorian Rudolph. An Unholy Trinity: TFNP, Polynomial Systems, and the Quantum Satisfiability Problem. In 17th Innovations in Theoretical Computer Science Conference (ITCS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 362, pp. 7:1-7:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{aldi_et_al:LIPIcs.ITCS.2026.7,
  author =	{Aldi, Marco and Gharibian, Sevag and Rudolph, Dorian},
  title =	{{An Unholy Trinity: TFNP, Polynomial Systems, and the Quantum Satisfiability Problem}},
  booktitle =	{17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
  pages =	{7:1--7:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-410-9},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{362},
  editor =	{Saraf, Shubhangi},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.7},
  URN =		{urn:nbn:de:0030-drops-252946},
  doi =		{10.4230/LIPIcs.ITCS.2026.7},
  annote =	{Keywords: quantum complexity theory, Quantum Merlin Arthur (QMA), Quantum Satisfiability Problem (QSAT), total function NP (TFNP)}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2025.5
Distributed Games with a Central Decision Maker

Authors: Bharat Adsul and Nehul Jain

Published in: LIPIcs, Volume 360, 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)

Abstract
We study distributed games played on non-deterministic asynchronous automata which feature a central decision maker process that participates in all key decision making tasks. In these partial-information games, processes use their causal past to respond to scheduling choices made by the scheduler and cooperatively strategize as a team to achieve the winning objective. We show that the problem of deciding the existence of a distributed winning strategy is efficiently solvable for global safety and local parity objectives. We provide algorithmic solutions that match their computational hardness. We formulate the notion of a finite-state distributed strategy which allows to quantify its distributed memory requirements. For the aforementioned objectives, we establish that finite-state distributed winning strategies always exist. In fact, we provide novel constructions of such winning strategies which are shown to have almost optimal amount of distributed memory. We also show that a natural extension of the model with two decision making processes is undecidable.
Cite as

Bharat Adsul and Nehul Jain. Distributed Games with a Central Decision Maker. In 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 360, pp. 5:1-5:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{adsul_et_al:LIPIcs.FSTTCS.2025.5,
  author =	{Adsul, Bharat and Jain, Nehul},
  title =	{{Distributed Games with a Central Decision Maker}},
  booktitle =	{45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)},
  pages =	{5:1--5:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-406-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{360},
  editor =	{Aiswarya, C. and Mehta, Ruta and Roy, Subhajit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2025.5},
  URN =		{urn:nbn:de:0030-drops-250843},
  doi =		{10.4230/LIPIcs.FSTTCS.2025.5},
  annote =	{Keywords: Mazurkiewicz traces, models of concurrency, distributed synthesis, game-theoretic models, asynchronous automata, distributed decision-making}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.MFCS.2025.5
On Synthesis of Distributed Monitors (Invited Talk)

Authors: Anca Muscholl

Published in: LIPIcs, Volume 345, 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)

Abstract
This talk addresses the synthesis problem of distributed monitors for concurrency properties.
Cite as

Anca Muscholl. On Synthesis of Distributed Monitors (Invited Talk). In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 5:1-5:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{muscholl:LIPIcs.MFCS.2025.5,
  author =	{Muscholl, Anca},
  title =	{{On Synthesis of Distributed Monitors}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{5:1--5:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-388-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{345},
  editor =	{Gawrychowski, Pawe{\l} and Mazowiecki, Filip and Skrzypczak, Micha{\l}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2025.5},
  URN =		{urn:nbn:de:0030-drops-241126},
  doi =		{10.4230/LIPIcs.MFCS.2025.5},
  annote =	{Keywords: Distributed synthesis, monitoring}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.51
Word Structures and Their Automatic Presentations

Authors: Xiaoyang Gong, Bakh Khoussainov, and Yuyang Zhuge

Published in: LIPIcs, Volume 345, 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)

Abstract
We study automatic presentations of the structures (ℕ; S), (ℕ; E_S), (ℕ; ≤), and their expansions by a unary predicate U. Here S is the successor function, E_S is the undirected version of S, and ≤ is the natural order. We call these structures word structures. Our goal is three-fold. First, we study the isomorphism problem for automatic word structures by focusing on the following three problems. The first problem asks to design an algorithm that, given an automatic structure A, decides if A is isomorphic to (ℕ; S). The second asks to design an algorithm that, given two automatic presentations of (ℕ; S, U₁) and (ℕ; S, U₂), where U₁ and U₂ are unary predicates, decides if these structures are isomorphic. The third problem investigates if there is an algorithm that, given two automatic presentations of (ℕ; ≤, U₁) and (ℕ; ≤, U₂), decides whether U₁ ∩ U₂ ≠ ∅. We show that these problems are undecidable. Next, we study intrinsic regularity of the function S in the structure Path_ω = (ℕ; E_S). We build an automatic presentation of Path_ω in which S is not regular. This implies that S is not intrinsically regular in Path_ω. For U ⊆ ℕ, let d_U be the function that computes the distances between the consecutive elements of U. We build automatic presentations of (ℕ; ≤, U) where d_U can realise logarithmic, radical, intermediate, and exponential functions.
Cite as

Xiaoyang Gong, Bakh Khoussainov, and Yuyang Zhuge. Word Structures and Their Automatic Presentations. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 51:1-51:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{gong_et_al:LIPIcs.MFCS.2025.51,
  author =	{Gong, Xiaoyang and Khoussainov, Bakh and Zhuge, Yuyang},
  title =	{{Word Structures and Their Automatic Presentations}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{51:1--51:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-388-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{345},
  editor =	{Gawrychowski, Pawe{\l} and Mazowiecki, Filip and Skrzypczak, Micha{\l}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2025.51},
  URN =		{urn:nbn:de:0030-drops-241581},
  doi =		{10.4230/LIPIcs.MFCS.2025.51},
  annote =	{Keywords: Automatic structures, the isomorphism problem, decidability, undecidability, regular relations}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2025.5
Characterizations of Fragments of Temporal Logic over Mazurkiewicz Traces

Authors: Bharat Adsul, Paul Gastin, and Shantanu Kulkarni

Published in: LIPIcs, Volume 348, 36th International Conference on Concurrency Theory (CONCUR 2025)

Abstract
We study fragments of temporal logics over Mazurkiewicz traces which are well known and established partial-order models of concurrent behaviours. We focus on concurrent versions of "strict past" and "strict future" modalities. Over words, the corresponding fragments have been shown to coincide with natural algebraic conditions on the recognizing monoids. We provide non-trivial generalizations of these classical results to traces. We exploit the local nature of the temporal modalities and obtain modular translations of specifications into asynchronous automata. More specifically, we provide novel characterizations of these fragments via local cascade products of a very simple two-state asynchronous automaton operating on a single process.
Cite as

Bharat Adsul, Paul Gastin, and Shantanu Kulkarni. Characterizations of Fragments of Temporal Logic over Mazurkiewicz Traces. In 36th International Conference on Concurrency Theory (CONCUR 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 348, pp. 5:1-5:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{adsul_et_al:LIPIcs.CONCUR.2025.5,
  author =	{Adsul, Bharat and Gastin, Paul and Kulkarni, Shantanu},
  title =	{{Characterizations of Fragments of Temporal Logic over Mazurkiewicz Traces}},
  booktitle =	{36th International Conference on Concurrency Theory (CONCUR 2025)},
  pages =	{5:1--5:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-389-8},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{348},
  editor =	{Bouyer, Patricia and van de Pol, Jaco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2025.5},
  URN =		{urn:nbn:de:0030-drops-239551},
  doi =		{10.4230/LIPIcs.CONCUR.2025.5},
  annote =	{Keywords: Mazurkiewicz traces, temporal logics, asynchronous automata, cascade product, Green’s relations, algebraic automata theory}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2025.19
Time for Timed Monitorability

Authors: Thomas M. Grosen, Sean Kauffman, Kim G. Larsen, and Martin Zimmermann

Published in: LIPIcs, Volume 348, 36th International Conference on Concurrency Theory (CONCUR 2025)

Abstract
Monitoring is an important part of the verification toolbox, in particular in situations where exhaustive verification using, e.g., model-checking is infeasible. The goal of online monitoring is to determine the satisfaction or violation of a specification during runtime, i.e., based on finite execution prefixes. However, not every specification is amenable to monitoring, e.g., properties for which no finite execution can witness satisfaction or violation. Monitorability is the question of whether a given specification is amenable to monitoring, and has been extensively studied in discrete time. Here, we study the monitorability problem for real-time properties expressed as Timed Automata. For specifications given by deterministic Timed Muller Automata, we prove decidability while we show that the problem is undecidable for specifications given by nondeterministic Timed Büchi automata. Furthermore, we refine monitorability to also determine bounds on the number of events as well as the time that must pass before monitoring the property may yield an informative verdict. We prove that for deterministic Timed Muller automata, such bounds can be effectively computed. In contrast we show that for nondeterministic Timed Büchi automata such bounds are not computable.
Cite as

Thomas M. Grosen, Sean Kauffman, Kim G. Larsen, and Martin Zimmermann. Time for Timed Monitorability. In 36th International Conference on Concurrency Theory (CONCUR 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 348, pp. 19:1-19:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{grosen_et_al:LIPIcs.CONCUR.2025.19,
  author =	{Grosen, Thomas M. and Kauffman, Sean and Larsen, Kim G. and Zimmermann, Martin},
  title =	{{Time for Timed Monitorability}},
  booktitle =	{36th International Conference on Concurrency Theory (CONCUR 2025)},
  pages =	{19:1--19:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-389-8},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{348},
  editor =	{Bouyer, Patricia and van de Pol, Jaco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2025.19},
  URN =		{urn:nbn:de:0030-drops-239690},
  doi =		{10.4230/LIPIcs.CONCUR.2025.19},
  annote =	{Keywords: Monitorability, Monitoring, Timed Automata, MITL}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2025.22
Partial-Order Reduction Is Hard

Authors: Frédéric Herbreteau, Sarah Larroze-Jardiné, and Igor Walukiewicz

Published in: LIPIcs, Volume 348, 36th International Conference on Concurrency Theory (CONCUR 2025)

Abstract
The goal of partial-order methods is to accelerate the exploration of concurrent systems by examining only a representative subset of all possible runs. The stateful approach builds a transition system with representative runs, while the stateless method simply enumerates them. The stateless approach may be preferable if the transition system is tree-like; otherwise, the stateful method is more effective. In the last decade, optimality has been a guiding principle for developing stateless partial-order reduction algorithms, and without doubt contributed to big progress in the field. In this paper we ask if we can get a similar principle for the stateful approach. We show that in stateful exploration, a polynomially close to optimal partial-order algorithm cannot exist unless P=NP. The result holds even for acyclic programs with just await instructions. This lower bound result justifies systematic study of heuristics for stateful partial-order reduction. We propose a notion of IFS oracle as a useful abstraction. The oracle can be used to get a very simple optimal stateless algorithm, which can then be adapted to a non-optimal stateful algorithm. While in general the oracle problem is NP-hard, we show a simple case where it can be solved in linear time.
Cite as

Frédéric Herbreteau, Sarah Larroze-Jardiné, and Igor Walukiewicz. Partial-Order Reduction Is Hard. In 36th International Conference on Concurrency Theory (CONCUR 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 348, pp. 22:1-22:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{herbreteau_et_al:LIPIcs.CONCUR.2025.22,
  author =	{Herbreteau, Fr\'{e}d\'{e}ric and Larroze-Jardin\'{e}, Sarah and Walukiewicz, Igor},
  title =	{{Partial-Order Reduction Is Hard}},
  booktitle =	{36th International Conference on Concurrency Theory (CONCUR 2025)},
  pages =	{22:1--22:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-389-8},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{348},
  editor =	{Bouyer, Patricia and van de Pol, Jaco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2025.22},
  URN =		{urn:nbn:de:0030-drops-239727},
  doi =		{10.4230/LIPIcs.CONCUR.2025.22},
  annote =	{Keywords: Formal verification, Concurrent systems, Partial-order reduction, Complexity}
}
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