22 Search Results for "Demri, Stéphane"

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.CSL.2026.8
Register-Bounded Synthesis from Constraint LTL

Authors: Nino Dauvier, Emmanuel Filiot, and Pierre-Alain Reynier

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

Abstract
We consider synthesis problems from logical specifications over infinite data domains, expressed in the logic constraint LTL (CLTL), which extends LTL with predicates over an infinite set of data values. We consider register-bounded synthesis, where the goal is to automatically generate, if it exists, a transducer with r registers that realizes a given CLTL formula, where r is also given as input. We prove that CLTL register-bounded synthesis is 2ExpTime-c for various data domains such as any infinite set with equality, (ℚ, <), and (ℕ, <). For the latter domain, this contrasts with known undecidability results of (unbounded) register CLTL synthesis, by Bhaskar and Praveen. Lastly, we consider synthesis in a partial observation setting by extending CLTL with invisible variables.
Cite as

Nino Dauvier, Emmanuel Filiot, and Pierre-Alain Reynier. Register-Bounded Synthesis from Constraint LTL. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{dauvier_et_al:LIPIcs.CSL.2026.8,
  author =	{Dauvier, Nino and Filiot, Emmanuel and Reynier, Pierre-Alain},
  title =	{{Register-Bounded Synthesis from Constraint LTL}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{8:1--8:18},
  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.2026.8},
  URN =		{urn:nbn:de:0030-drops-254322},
  doi =		{10.4230/LIPIcs.CSL.2026.8},
  annote =	{Keywords: Synthesis, Data words, Constraint linear time logic, Register transducer}
}
Document
DOI: 10.4230/LIPIcs.CSL.2026.16
On the Entailment Problem in Dynamic Separation Logic with Inductive Definitions

Authors: Nicolas Peltier

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

Abstract
Separation Logic (SL) is a well-established framework for reasoning about programs that manipulate dynamic memory. To express and verify properties of custom recursive data structures, SL is extended with spatial predicates defined by user-specified inductive rules. Many verification problems reduce to deciding entailments between formulas involving these predicates. While the general entailment problem is undecidable, a broad class of inductive rules - known as PCE (Progressing, Connected, and Established) - has been identified for which entailment is decidable. In this work, we extend the study of the entailment problem to Dynamic Separation Logic (DSL), an extension of SL that includes dynamic modalities for reasoning about actions on the heap and store. We show that entailment in DSL remains decidable for PCE rules by proving that dynamic modalities can be automatically eliminated.
Cite as

Nicolas Peltier. On the Entailment Problem in Dynamic Separation Logic with Inductive Definitions. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 16:1-16:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{peltier:LIPIcs.CSL.2026.16,
  author =	{Peltier, Nicolas},
  title =	{{On the Entailment Problem in Dynamic Separation Logic with Inductive Definitions}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{16:1--16:20},
  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.2026.16},
  URN =		{urn:nbn:de:0030-drops-254402},
  doi =		{10.4230/LIPIcs.CSL.2026.16},
  annote =	{Keywords: Separation logic, Dynamic logic, Entailment problem}
}
Document
DOI: 10.4230/LIPIcs.CSL.2026.23
A Logic for Fresh Labelled Transition Systems

Authors: Mohamed H. Bandukara and Nikos Tzevelekos

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

Abstract
We introduce a Hennessy-Milner logic with recursion for Fresh Labelled Transition Systems (FLTSs). These are nominal labelled transition systems which keep track of the history, i.e. of data values seen so far, and can model fresh data generation. In particular, FLTSs generalise the computations of Fresh-Register Automata, which in turn can be seen as a "regular" class of history-tracking automata operating on infinite input alphabets. The logic we introduce is a modal mu-calculus equipped with infinite disjunctions over arbitrary and fresh data values respectively, while its recursion is parameterised on vectors of data values. It can express a variety of properties, such as the existence of an infinite path of distinct data values, the absence of paths where values are repeated, or the existence of a finite path where some taint property is violated. We study the model-checking problem and its complexity via a reduction to parity games and, using nominal sets techniques, provide an exponential upper bound for it.
Cite as

Mohamed H. Bandukara and Nikos Tzevelekos. A Logic for Fresh Labelled Transition Systems. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 23:1-23:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{bandukara_et_al:LIPIcs.CSL.2026.23,
  author =	{Bandukara, Mohamed H. and Tzevelekos, Nikos},
  title =	{{A Logic for Fresh Labelled Transition Systems}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{23:1--23:24},
  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.2026.23},
  URN =		{urn:nbn:de:0030-drops-254478},
  doi =		{10.4230/LIPIcs.CSL.2026.23},
  annote =	{Keywords: Nominal Transition Systems, Hennessy-Milner Logic, Modal Mu-Calculus, Register Automata, Nominal Sets, Parity Games}
}
Document
DOI: 10.4230/LIPIcs.CSL.2026.42
Robustness of Constraint Automata for Description Logics with Concrete Domains

Authors: Stéphane Demri and Tianwen Gu

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

Abstract
Decidability or complexity issues about the consistency problem for description logics with concrete domains have already been analysed with tableaux-based or type elimination methods. Concrete domains in ontologies are essential to consider concrete objects and predefined relations. In this work, we expose an automata-based approach leading to the optimal upper bound ExpTime, that is designed by enriching the transitions with symbolic constraints. We show that the nonemptiness problem for such automata belongs to ExpTime if the concrete domains satisfy a few simple properties. Then, we provide a reduction from the consistency problem for ontologies, yielding ExpTime-membership. Thanks to the expressivity of constraint automata, the results are extended to additional ingredients such as inverse roles, functional role names and constraint assertions, while maintaining ExpTime-membership, which illustrates the robustness of the approach.
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Stéphane Demri and Tianwen Gu. Robustness of Constraint Automata for Description Logics with Concrete Domains. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 42:1-42:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{demri_et_al:LIPIcs.CSL.2026.42,
  author =	{Demri, St\'{e}phane and Gu, Tianwen},
  title =	{{Robustness of Constraint Automata for Description Logics with Concrete Domains}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{42:1--42:18},
  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.2026.42},
  URN =		{urn:nbn:de:0030-drops-254679},
  doi =		{10.4230/LIPIcs.CSL.2026.42},
  annote =	{Keywords: Description logics, concrete domains, constraint automata, complexity}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2025.14
Regulating Synchronous Data Exchange to Meet Control Flow and Data Specifications

Authors: Ashwin Bhaskar and M. Praveen

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

Abstract
When multiple software components interact via method calls, we may want to ensure that the order of invoked methods and the arguments provided adhere to some specification. The classic problem associated with interface automata checks for the existence of a mediator whose intention is to act as a buffer in between method invocations so that invocations do not go unanswered. We extend the base model underlying interface automata, enabling them to exchange integer values - one automaton generates an integer value and outputs it by firing a generating transition and another automaton receives the value by synchronously firing a receiving transition. Transitions in the automata can have guards with linear order constraints on the exchanged values, influencing which methods can or can not be invoked later. So the generated values influence the sequences of invocations that are enabled. We specify desirable properties of the sequence of method calls and the arguments passed to them using an extension of Linear Temporal Logic (LTL). We consider the interoperability problem, which is to check if it is possible to generate integer values in such a way that all enabled sequences satisfy the given specification. We show that the interoperability problem is undecidable in general, even when there are only two participating automata. We show decidability in the case where guards on generating transitions can only have equality constraints on the exchanged value (but receiving transitions can continue to have linear order constraints). We model this problem as a game between two players, one trying to generate integer values such that violating sequences are disabled while the other player tries to dig out violating sequences that are enabled. Interoperability is equivalent to the first player having a winning strategy. We solve this game via a finite abstraction, which results in a symbolic game. We then show that winning strategies for the symbolic game can be translated to winning strategies for the original game over integers.
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Ashwin Bhaskar and M. Praveen. Regulating Synchronous Data Exchange to Meet Control Flow and Data Specifications. 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. 14:1-14:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bhaskar_et_al:LIPIcs.FSTTCS.2025.14,
  author =	{Bhaskar, Ashwin and Praveen, M.},
  title =	{{Regulating Synchronous Data Exchange to Meet Control Flow and Data Specifications}},
  booktitle =	{45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)},
  pages =	{14:1--14:19},
  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.2025.14},
  URN =		{urn:nbn:de:0030-drops-250962},
  doi =		{10.4230/LIPIcs.FSTTCS.2025.14},
  annote =	{Keywords: Distributed Systems, Interface Automata, Registers, Parity Games}
}
Document
Invited Paper
DOI: 10.4230/OASIcs.RW.2024/2025.6
Explaining Reasoning Results for Description Logic Ontologies (Invited Paper)

Authors: Patrick Koopmann

Published in: OASIcs, Volume 138, Joint Proceedings of the 20th and 21st Reasoning Web Summer Schools (RW 2024 & RW 2025)

Abstract
The Web Ontology Language (OWL), grounded in description logics, enables reasoning systems to infer implicit knowledge in a transparent manner. However, the expressivity of description logics and the complexity of large ontologies often results in reasoning outcomes that are hard to understand without additional tool support. Explanations of these outcomes are essential for users to understand ontology content, communicate its structure and behavior effectively, and debug undesired or missing inferences. This chapter provides an overview of the central explanation techniques that have been developed for explaining reasoning with description logic ontologies. Here, we consider both explanations for positive entailments (explaining why something can be deduced), as well as negative entailments (why something cannot be deduced). More specifically, we discuss justifications, proofs and interpolation as a means to explain positive entailments, and abduction for explaining negative entailments, where we also have a closer look at practical algorithms as well as practical and theoretical challenges.
Cite as

Patrick Koopmann. Explaining Reasoning Results for Description Logic Ontologies (Invited Paper). In Joint Proceedings of the 20th and 21st Reasoning Web Summer Schools (RW 2024 & RW 2025). Open Access Series in Informatics (OASIcs), Volume 138, pp. 6:1-6:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{koopmann:OASIcs.RW.2024/2025.6,
  author =	{Koopmann, Patrick},
  title =	{{Explaining Reasoning Results for Description Logic Ontologies}},
  booktitle =	{Joint Proceedings of the 20th and 21st Reasoning Web Summer Schools (RW 2024 \& RW 2025)},
  pages =	{6:1--6:29},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-405-5},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{138},
  editor =	{Artale, Alessandro and Bienvenu, Meghyn and Garc{\'\i}a, Yazm{\'\i}n Ib\'{a}\~{n}ez and Murlak, Filip},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.RW.2024/2025.6},
  URN =		{urn:nbn:de:0030-drops-250514},
  doi =		{10.4230/OASIcs.RW.2024/2025.6},
  annote =	{Keywords: Explanations, Justifications, Proofs, Craig Interpolation, Contrastive Explanations}
}
Document
DOI: 10.4230/LIPIcs.TIME.2025.5
Higher-Order Timed Automata and Tail Recursion

Authors: Florian Bruse

Published in: LIPIcs, Volume 355, 32nd International Symposium on Temporal Representation and Reasoning (TIME 2025)

Abstract
Timed Automata (TA) are a popular formalism to model systems in dense linear time. However, due to their finite state-space, they can only model systems with a finitary logical behavior. There are extensions to e.g., timed pushdown systems and timed recursive state machines. Higher-Order Recursion Schemes (HORS) are another popular model for infinite-state, non-regular systems, naturally stratified by their type-theoretic order. We recently introduced Real-Time Recursion schemes as an approximation of HORS to real-time systems. This paper updates Real-Time Recursion Schemes into Higher-Order Timed Automata, a formalism that defines a tree-shaped timed automaton, which is more suitable to model actual systems. We show that the model-checking problem against the timed version of the modal mu-calculus exhibits the expected complexity bounds, i.e., an increase by one exponential towards the untimed version. We also show that, in the presence of tail recursion, half an exponential can be recovered, mirroring similar gains in the untimed setting. We also give a matching lower bound for the special case of order-1 HORTA. We conjecture that this can be generalized for all orders.
Cite as

Florian Bruse. Higher-Order Timed Automata and Tail Recursion. In 32nd International Symposium on Temporal Representation and Reasoning (TIME 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 355, pp. 5:1-5:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bruse:LIPIcs.TIME.2025.5,
  author =	{Bruse, Florian},
  title =	{{Higher-Order Timed Automata and Tail Recursion}},
  booktitle =	{32nd International Symposium on Temporal Representation and Reasoning (TIME 2025)},
  pages =	{5:1--5:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-401-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{355},
  editor =	{Vidal, Thierry and Wa{\l}\k{e}ga, Przemys{\l}aw Andrzej},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TIME.2025.5},
  URN =		{urn:nbn:de:0030-drops-244519},
  doi =		{10.4230/LIPIcs.TIME.2025.5},
  annote =	{Keywords: Timed Automata, Higher-Order Recursion Schemes, Tree Automata, Tail Recursion}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.14
Register Automata with Permutations

Authors: Mrudula Balachander, Emmanuel Filiot, Raffaella Gentilini, and Nikos Tzevelekos

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

Abstract
We propose Permutation Deterministic Register Automata (pDRAs), a deterministic register automaton model where we allow permutations of registers in transitions. The model enables minimal canonical representations and pDRAs can be tested for equivalence in polynomial time. The complexity of minimization is between GI (the complexity of graph isomorphism) and NP. We then introduce a subclass of pDRAs, called register automata with fixed permutation policy, where the register permutation discipline is stipulated globally. This class generalizes the model proposed by Benedikt, Ley and Puppis in 2010, and we show that it also admits minimal and canonical representations, based on a finite-index word equivalence relation. As an application, we show that for any regular data language L, the minimal register automaton with fixed permutation policy recognizing L can be actively learned in polynomial time using oracles for membership, equivalence and data-memorability queries. We show that all the oracles can be implemented in polynomial time, and so this yields a polynomial time minimization algorithm.
Cite as

Mrudula Balachander, Emmanuel Filiot, Raffaella Gentilini, and Nikos Tzevelekos. Register Automata with Permutations. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 14:1-14:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{balachander_et_al:LIPIcs.MFCS.2025.14,
  author =	{Balachander, Mrudula and Filiot, Emmanuel and Gentilini, Raffaella and Tzevelekos, Nikos},
  title =	{{Register Automata with Permutations}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{14:1--14:18},
  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.2025.14},
  URN =		{urn:nbn:de:0030-drops-241219},
  doi =		{10.4230/LIPIcs.MFCS.2025.14},
  annote =	{Keywords: Register automata, data words, equivalence, minimization, active learning}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.38
The Complexity of Separability for Semilinear Sets and Parikh Automata

Authors: Elias Rojas Collins, Chris Köcher, and Georg Zetzsche

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

Abstract
In a separability problem, we are given two sets K and L from a class 𝒞, and we want to decide whether there exists a set S from a class 𝒮 such that K ⊆ S and S ∩ L = ∅. In this case, we speak of separability of sets in 𝒞 by sets in 𝒮. We study two types of separability problems. First, we consider separability of semilinear sets (i.e. subsets of ℕ^d for some d) by sets definable by quantifier-free monadic Presburger formulas (or equivalently, the recognizable subsets of ℕ^d). Here, a formula is monadic if each atom uses at most one variable. Second, we consider separability of languages of Parikh automata by regular languages. A Parikh automaton is a machine with access to counters that can only be incremented, and have to meet a semilinear constraint at the end of the run. Both of these separability problems are known to be decidable with elementary complexity. Our main results are that both problems are coNP-complete. In the case of semilinear sets, coNP-completeness holds regardless of whether the input sets are specified by existential Presburger formulas, quantifier-free formulas, or semilinear representations. Our results imply that recognizable separability of rational subsets of Σ* × ℕ^d (shown decidable by Choffrut and Grigorieff) is coNP-complete as well. Another application is that regularity of deterministic Parikh automata (where the target set is specified using a quantifier-free Presburger formula) is coNP-complete as well.
Cite as

Elias Rojas Collins, Chris Köcher, and Georg Zetzsche. The Complexity of Separability for Semilinear Sets and Parikh Automata. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 38:1-38:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{collins_et_al:LIPIcs.MFCS.2025.38,
  author =	{Collins, Elias Rojas and K\"{o}cher, Chris and Zetzsche, Georg},
  title =	{{The Complexity of Separability for Semilinear Sets and Parikh Automata}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{38:1--38:21},
  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.2025.38},
  URN =		{urn:nbn:de:0030-drops-241457},
  doi =		{10.4230/LIPIcs.MFCS.2025.38},
  annote =	{Keywords: Vector Addition System, Separability, Regular Language}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.22
On the Reachability Problem for Two-Dimensional Branching VASS

Authors: Clotilde Bizière, Thibault Hilaire, Jérôme Leroux, and Grégoire Sutre

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

Abstract
Vectors addition systems with states (VASS), or equivalently Petri nets, are arguably one of the most studied formalisms for the modeling and analysis of concurrent systems. A central decision problem for VASS is reachability: whether there exists a run from an initial configuration to a final one. This problem has been known to be decidable for over forty years, and its complexity has recently been precisely characterized. Our work concerns the reachability problem for BVASS, a branching generalization of VASS. In dimension one, the exact complexity of this problem is known. In this paper, we prove that the reachability problem for 2-dimensional BVASS is decidable. In fact, we even show that the reachability set admits a computable semilinear presentation. The decidability status of the reachability problem for BVASS remains open in higher dimensions.
Cite as

Clotilde Bizière, Thibault Hilaire, Jérôme Leroux, and Grégoire Sutre. On the Reachability Problem for Two-Dimensional Branching VASS. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 22:1-22:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{biziere_et_al:LIPIcs.MFCS.2025.22,
  author =	{Bizi\`{e}re, Clotilde and Hilaire, Thibault and Leroux, J\'{e}r\^{o}me and Sutre, Gr\'{e}goire},
  title =	{{On the Reachability Problem for Two-Dimensional Branching VASS}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{22:1--22:19},
  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.2025.22},
  URN =		{urn:nbn:de:0030-drops-241294},
  doi =		{10.4230/LIPIcs.MFCS.2025.22},
  annote =	{Keywords: Vector addition systems, Reachability problem, Semilinear sets, Verification}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2025.4
Monitorability for the Modal Mu-Calculus over Systems with Data: From Practice to Theory

Authors: Luca Aceto, Antonis Achilleos, Duncan Paul Attard, Léo Exibard, Adrian Francalanza, Anna Ingólfsdóttir, and Karoliina Lehtinen

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

Abstract
Runtime verification consists in checking whether a system satisfies a given specification by observing the execution trace it produces. In the regular setting, the modal μ-calculus provides a versatile formalism for expressing specifications of the control flow of the system. This paper focuses on the data flow and studies an extension of that logic that allows it to express data-dependent properties, identifying fragments that can be verified at runtime and with what correctness guarantees. The logic studied here is closely related with register automata with guessing. That correspondence yields a monitor synthesis algorithm, and a strict hierarchy among the various fragments of the logic, in contrast to the regular setting. We then exhibit a fragment of the logic that can express all monitorable formulae in the logic without greatest fixed-points but not in the full logic, and show this is the best we can get.
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Luca Aceto, Antonis Achilleos, Duncan Paul Attard, Léo Exibard, Adrian Francalanza, Anna Ingólfsdóttir, and Karoliina Lehtinen. Monitorability for the Modal Mu-Calculus over Systems with Data: From Practice to Theory. In 36th International Conference on Concurrency Theory (CONCUR 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 348, pp. 4:1-4:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{aceto_et_al:LIPIcs.CONCUR.2025.4,
  author =	{Aceto, Luca and Achilleos, Antonis and Attard, Duncan Paul and Exibard, L\'{e}o and Francalanza, Adrian and Ing\'{o}lfsd\'{o}ttir, Anna and Lehtinen, Karoliina},
  title =	{{Monitorability for the Modal Mu-Calculus over Systems with Data: From Practice to Theory}},
  booktitle =	{36th International Conference on Concurrency Theory (CONCUR 2025)},
  pages =	{4:1--4:21},
  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.2025.4},
  URN =		{urn:nbn:de:0030-drops-239546},
  doi =		{10.4230/LIPIcs.CONCUR.2025.4},
  annote =	{Keywords: Runtime verification, monitorability, \muHML with data, register automata}
}
Document
DOI: 10.4230/LIPIcs.SAT.2025.11
Better Extension Variables in DQBF via Independence

Authors: Leroy Chew and Tomáš Peitl

Published in: LIPIcs, Volume 341, 28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025)

Abstract
We show that extension variables in (D)QBF can be generalised by conditioning on universal assignments. The benefit of this is that the dependency sets of such conditioned extension variables can be made smaller to allow easier refutations. This simple modification instantly solves many challenges in p-simulating the QBF expansion rule, which cannot be p-simulated in proof systems that have strategy extraction [Leroy Chew and Judith Clymo, 2020]. Simulating expansion is even more crucial in DQBF, where other methods are incomplete. In this paper we provide an overview of the strength of this new independent extension rule. We find that a new version of Extended Frege called IndExtFrege + ∀red can p-simulate a multitude of difficult QBF and DQBF techniques, even techniques that are difficult to approach with eFrege + ∀red. We show five p-simulations, that IndExtFrege + ∀red p-simulates QRAT, DQBF-IR-calc, IR(𝒟^rrs)-calc, Fork-Resolution and DQRAT which together underpin most DQBF solving and preprocessing techniques. The p-simulations work despite these systems using complicated rules and our new extension rule being relatively simple. Moreover, unlike recent p-simulations by eFrege + ∀red we can simulate the proof rules line by line, which allows us to mix QBF rules more easily with other inference steps.
Cite as

Leroy Chew and Tomáš Peitl. Better Extension Variables in DQBF via Independence. In 28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 341, pp. 11:1-11:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{chew_et_al:LIPIcs.SAT.2025.11,
  author =	{Chew, Leroy and Peitl, Tom\'{a}\v{s}},
  title =	{{Better Extension Variables in DQBF via Independence}},
  booktitle =	{28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025)},
  pages =	{11:1--11:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-381-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{341},
  editor =	{Berg, Jeremias and Nordstr\"{o}m, Jakob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SAT.2025.11},
  URN =		{urn:nbn:de:0030-drops-237453},
  doi =		{10.4230/LIPIcs.SAT.2025.11},
  annote =	{Keywords: DQBF, QBF, Proof Systems, Dependency Schemes, RAT, Extended Frege, Skolem functions}
}
Document
DOI: 10.4230/LIPIcs.CALCO.2025.9
Safety and Strong Completeness via Reducibility for Many-Valued Coalgebraic Dynamic Logics

Authors: Helle Hvid Hansen and Wolfgang Poiger

Published in: LIPIcs, Volume 342, 11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)

Abstract
We present a coalgebraic framework for studying generalisations of dynamic modal logics such as PDL and game logic in which both the propositions and the semantic structures can take values in an algebra 𝐀 of truth-degrees. More precisely, we work with coalgebraic modal logic via 𝐀-valued predicate liftings where 𝐀 is an FLew-algebra, and interpret actions (abstracting programs and games) as 𝖥-coalgebras where the functor 𝖥 represents some type of 𝐀-weighted system. We also allow combinations of crisp propositions with 𝐀-weighted systems and vice versa. We introduce coalgebra operations and tests, with a focus on operations which are reducible in the sense that modalities for composed actions can be reduced to compositions of modalities for the constituent actions. We prove that reducible operations are safe for bisimulation and behavioural equivalence, and prove a general strong completeness result, from which we obtain new strong completeness results for 𝟐-valued iteration-free PDL with 𝐀-valued accessibility relations when 𝐀 is a finite chain, and for many-valued iteration-free game logic with many-valued strategies based on finite Lukasiewicz logic.
Cite as

Helle Hvid Hansen and Wolfgang Poiger. Safety and Strong Completeness via Reducibility for Many-Valued Coalgebraic Dynamic Logics. In 11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 342, pp. 9:1-9:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{hansen_et_al:LIPIcs.CALCO.2025.9,
  author =	{Hansen, Helle Hvid and Poiger, Wolfgang},
  title =	{{Safety and Strong Completeness via Reducibility for Many-Valued Coalgebraic Dynamic Logics}},
  booktitle =	{11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)},
  pages =	{9:1--9:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-383-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{342},
  editor =	{C\^{i}rstea, Corina and Knapp, Alexander},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2025.9},
  URN =		{urn:nbn:de:0030-drops-235681},
  doi =		{10.4230/LIPIcs.CALCO.2025.9},
  annote =	{Keywords: dynamic logic, many-valued coalgebraic logic, safety, strong completeness}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2025.31
On Deciding the Data Complexity of Answering Linear Monadic Datalog Queries with LTL Operators

Authors: Alessandro Artale, Anton Gnatenko, Vladislav Ryzhikov, and Michael Zakharyaschev

Published in: LIPIcs, Volume 328, 28th International Conference on Database Theory (ICDT 2025)

Abstract
Our concern is the data complexity of answering linear monadic datalog queries whose atoms in the rule bodies can be prefixed by operators of linear temporal logic LTL. We first observe that, for data complexity, answering any connected query with operators ○/○- (at the next/previous moment) is either in AC⁰, or in ACC⁰\AC⁰, or NC¹-complete, or L-hard and in NL. Then we show that the problem of deciding L-hardness of answering such queries is PSpace-complete, while checking membership in the classes AC⁰ and ACC⁰ as well as NC¹-completeness can be done in ExpSpace. Finally, we prove that membership in AC⁰ or in ACC⁰, NC¹-completeness, and L-hardness are undecidable for queries with operators ◇/◇- (sometime in the future/past) provided that NC¹ ≠ NL and L ≠ NL.
Cite as

Alessandro Artale, Anton Gnatenko, Vladislav Ryzhikov, and Michael Zakharyaschev. On Deciding the Data Complexity of Answering Linear Monadic Datalog Queries with LTL Operators. In 28th International Conference on Database Theory (ICDT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 328, pp. 31:1-31:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{artale_et_al:LIPIcs.ICDT.2025.31,
  author =	{Artale, Alessandro and Gnatenko, Anton and Ryzhikov, Vladislav and Zakharyaschev, Michael},
  title =	{{On Deciding the Data Complexity of Answering Linear Monadic Datalog Queries with LTL Operators}},
  booktitle =	{28th International Conference on Database Theory (ICDT 2025)},
  pages =	{31:1--31:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-364-5},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{328},
  editor =	{Roy, Sudeepa and Kara, Ahmet},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2025.31},
  URN =		{urn:nbn:de:0030-drops-229723},
  doi =		{10.4230/LIPIcs.ICDT.2025.31},
  annote =	{Keywords: Linear monadic datalog, linear temporal logic, data complexity}
}
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