463 Search Results for "Ben-Or, Michael"

Document
DOI: 10.4230/DagRep.13.9.103
Roadmap for Responsible Robotics (Dagstuhl Seminar 23371)

Authors: Michael Fisher, Marija Slavkovik, Anna Dobrosovestnova, and Nick Schuster

Published in: Dagstuhl Reports, Volume 13, Issue 9 (2024)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 23371 "Roadmap for Responsible Robotics". The seminar was concerned with robots across all their forms, particularly autonomous robots capable of making their own decisions and taking their own actions without direct human oversight. The seminar brought together experts in computer science, robotics, engineering, philosophy, cognitive science, human-robot interactions, as well as representatives of the industry, with the aim of contributing to the steps towards ethical and responsible robotic systems as initiated by actors such as the European Robotics Research Network (EURON), the European Union’s REELER, and others. We discussed topics including: "Why do autonomous robots warrant distinct normative considerations?", "Which stakeholders are, or should be, involved in the development and deployment of robotic systems, and how do we configure their responsibilities?", "What are the principal tenets of responsible robotics beyond commonly associated themes, namely trust, fairness, predictability and understandability?". Through intensive discussions of these and other related questions, motivated by the various values at stake as robotic systems become increasingly present and impactful in human life, this interdisciplinary group identified a set of interrelated priorities to guide future research and regulatory efforts. The resulting roadmap aimed to ensure that robotic systems co-evolve with human societies so as to advance, rather than undermine, human agency and humane values.
Cite as

Michael Fisher, Marija Slavkovik, Anna Dobrosovestnova, and Nick Schuster. Roadmap for Responsible Robotics (Dagstuhl Seminar 23371). In Dagstuhl Reports, Volume 13, Issue 9, pp. 103-115, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@Article{fisher_et_al:DagRep.13.9.103,
  author =	{Fisher, Michael and Slavkovik, Marija and Dobrosovestnova, Anna and Schuster, Nick},
  title =	{{Roadmap for Responsible Robotics (Dagstuhl Seminar 23371)}},
  pages =	{103--115},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2024},
  volume =	{13},
  number =	{9},
  editor =	{Fisher, Michael and Slavkovik, Marija and Dobrosovestnova, Anna and Schuster, Nick},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.13.9.103},
  URN =		{urn:nbn:de:0030-drops-198223},
  doi =		{10.4230/DagRep.13.9.103},
  annote =	{Keywords: Robotics, Responsibility, Trust, Fairness, Predictability, Understandability, Ethics}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.ICDT.2024.3
Rule-Based Ontologies: From Semantics to Syntax (Invited Talk)

Authors: Andreas Pieris

Published in: LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024)

Abstract
An ontology specifies an abstract model of a domain of interest via a formal language that is typically based on logic. Tuple-generating dependencies (tgds) and equality-generating dependencies (egds) originally introduced as a unifying framework for database integrity constraints, and later on used in data exchange and integration, are well suited for modeling ontologies that are intended for data-intensive tasks. The reason is that, unlike other popular formalisms such as description logics, tgds and egds can easily handle higher-arity relations that naturally occur in relational databases. In recent years, there has been an extensive study of tgd- and egd-based ontologies and of their applications to several different data-intensive tasks. In those studies, model theory plays a crucial role and it typically proceeds from syntax to semantics. In other words, the syntax of an ontology language is introduced first and then the properties of the mathematical structures that satisfy ontologies of that language are explored. There is, however, a mature and growing body of research in the reverse direction, i.e., from semantics to syntax. Here, the starting point is a collection of model-theoretic properties and the goal is to determine whether or not these properties characterize some ontology language. Such results are welcome as they pinpoint the expressive power of an ontology language in terms of insightful model-theoretic properties. The main aim of this tutorial is to present a comprehensive overview of model-theoretic characterizations of tgd- and egd-based ontology languages that are encountered in database theory and symbolic artificial intelligence.
Cite as

Andreas Pieris. Rule-Based Ontologies: From Semantics to Syntax (Invited Talk). In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, p. 3:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{pieris:LIPIcs.ICDT.2024.3,
  author =	{Pieris, Andreas},
  title =	{{Rule-Based Ontologies: From Semantics to Syntax}},
  booktitle =	{27th International Conference on Database Theory (ICDT 2024)},
  pages =	{3:1--3:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-312-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{290},
  editor =	{Cormode, Graham and Shekelyan, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.3},
  URN =		{urn:nbn:de:0030-drops-197857},
  doi =		{10.4230/LIPIcs.ICDT.2024.3},
  annote =	{Keywords: ontologies, tuple-generating dependencies, equality-generating dependencies, model theory, model-theoretic characterizations}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2024.6
Range Entropy Queries and Partitioning

Authors: Sanjay Krishnan and Stavros Sintos

Published in: LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024)

Abstract
Data partitioning that maximizes or minimizes Shannon entropy is a crucial subroutine in data compression, columnar storage, and cardinality estimation algorithms. These partition algorithms can be accelerated if we have a data structure to find the entropy in different subsets of data when the algorithm needs to decide what block to construct. While it is generally known how to compute the entropy of a discrete distribution efficiently, we want to efficiently derive the entropy among the data items that lie in a specific area. We solve this problem in a typical setting when we deal with real data, where data items are geometric points and each requested area is a query (hyper)rectangle. More specifically, we consider a set P of n weighted and colored points in ℝ^d. The goal is to construct a low space data structure, such that given a query (hyper)rectangle R, it computes the entropy based on the colors of the points in P∩ R, in sublinear time. We show a conditional lower bound for this problem proving that we cannot hope for data structures with near-linear space and near-constant query time. Then, we propose exact data structures for d = 1 and d > 1 with o(n^{2d}) space and o(n) query time. We also provide a tune parameter t that the user can choose to bound the asymptotic space and query time of the new data structures. Next, we propose near linear space data structures for returning either an additive or a multiplicative approximation of the entropy. Finally, we show how we can use the new data structures to efficiently partition time series and histograms with respect to entropy.
Cite as

Sanjay Krishnan and Stavros Sintos. Range Entropy Queries and Partitioning. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 6:1-6:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{krishnan_et_al:LIPIcs.ICDT.2024.6,
  author =	{Krishnan, Sanjay and Sintos, Stavros},
  title =	{{Range Entropy Queries and Partitioning}},
  booktitle =	{27th International Conference on Database Theory (ICDT 2024)},
  pages =	{6:1--6:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-312-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{290},
  editor =	{Cormode, Graham and Shekelyan, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.6},
  URN =		{urn:nbn:de:0030-drops-197883},
  doi =		{10.4230/LIPIcs.ICDT.2024.6},
  annote =	{Keywords: Shannon entropy, range query, data structure, data partitioning}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2024.7
Skyline Operators for Document Spanners

Authors: Antoine Amarilli, Benny Kimelfeld, Sébastien Labbé, and Stefan Mengel

Published in: LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024)

Abstract
When extracting a relation of spans (intervals) from a text document, a common practice is to filter out tuples of the relation that are deemed dominated by others. The domination rule is defined as a partial order that varies along different systems and tasks. For example, we may state that a tuple is dominated by tuples that extend it by assigning additional attributes, or assigning larger intervals. The result of filtering the relation would then be the skyline according to this partial order. As this filtering may remove most of the extracted tuples, we study whether we can improve the performance of the extraction by compiling the domination rule into the extractor. To this aim, we introduce the skyline operator for declarative information extraction tasks expressed as document spanners. We show that this operator can be expressed via regular operations when the domination partial order can itself be expressed as a regular spanner, which covers several natural domination rules. Yet, we show that the skyline operator incurs a computational cost (under combined complexity). First, there are cases where the operator requires an exponential blowup on the number of states needed to represent the spanner as a sequential variable-set automaton. Second, the evaluation may become computationally hard. Our analysis more precisely identifies classes of domination rules for which the combined complexity is tractable or intractable.
Cite as

Antoine Amarilli, Benny Kimelfeld, Sébastien Labbé, and Stefan Mengel. Skyline Operators for Document Spanners. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 7:1-7:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{amarilli_et_al:LIPIcs.ICDT.2024.7,
  author =	{Amarilli, Antoine and Kimelfeld, Benny and Labb\'{e}, S\'{e}bastien and Mengel, Stefan},
  title =	{{Skyline Operators for Document Spanners}},
  booktitle =	{27th International Conference on Database Theory (ICDT 2024)},
  pages =	{7:1--7:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-312-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{290},
  editor =	{Cormode, Graham and Shekelyan, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.7},
  URN =		{urn:nbn:de:0030-drops-197898},
  doi =		{10.4230/LIPIcs.ICDT.2024.7},
  annote =	{Keywords: Information Extraction, Document Spanners, Query Evaluation}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2024.8
When Do Homomorphism Counts Help in Query Algorithms?

Authors: Balder ten Cate, Victor Dalmau, Phokion G. Kolaitis, and Wei-Lin Wu

Published in: LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024)

Abstract
A query algorithm based on homomorphism counts is a procedure for determining whether a given instance satisfies a property by counting homomorphisms between the given instance and finitely many predetermined instances. In a left query algorithm, we count homomorphisms from the predetermined instances to the given instance, while in a right query algorithm we count homomorphisms from the given instance to the predetermined instances. Homomorphisms are usually counted over the semiring ℕ of non-negative integers; it is also meaningful, however, to count homomorphisms over the Boolean semiring 𝔹, in which case the homomorphism count indicates whether or not a homomorphism exists. We first characterize the properties that admit a left query algorithm over 𝔹 by showing that these are precisely the properties that are both first-order definable and closed under homomorphic equivalence. After this, we turn attention to a comparison between left query algorithms over 𝔹 and left query algorithms over ℕ. In general, there are properties that admit a left query algorithm over ℕ but not over 𝔹. The main result of this paper asserts that if a property is closed under homomorphic equivalence, then that property admits a left query algorithm over 𝔹 if and only if it admits a left query algorithm over ℕ. In other words and rather surprisingly, homomorphism counts over ℕ do not help as regards properties that are closed under homomorphic equivalence. Finally, we characterize the properties that admit both a left query algorithm over 𝔹 and a right query algorithm over 𝔹.
Cite as

Balder ten Cate, Victor Dalmau, Phokion G. Kolaitis, and Wei-Lin Wu. When Do Homomorphism Counts Help in Query Algorithms?. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 8:1-8:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{tencate_et_al:LIPIcs.ICDT.2024.8,
  author =	{ten Cate, Balder and Dalmau, Victor and Kolaitis, Phokion G. and Wu, Wei-Lin},
  title =	{{When Do Homomorphism Counts Help in Query Algorithms?}},
  booktitle =	{27th International Conference on Database Theory (ICDT 2024)},
  pages =	{8:1--8:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-312-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{290},
  editor =	{Cormode, Graham and Shekelyan, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.8},
  URN =		{urn:nbn:de:0030-drops-197905},
  doi =		{10.4230/LIPIcs.ICDT.2024.8},
  annote =	{Keywords: query algorithms, homomorphism, homomorphism counts, conjunctive query, constraint satisfaction}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2024.17
Containment of Regular Path Queries Under Path Constraints

Authors: Sylvain Salvati and Sophie Tison

Published in: LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024)

Abstract
Data integrity is ensured by expressing constraints it should satisfy. One can also view constraints as data properties and take advantage of them for several tasks such as reasoning about data or accelerating query processing. In the context of graph databases, simple constraints can be expressed by means of path constraints while simple queries are modeled as regular path queries (RPQs). In this paper, we investigate the containment of RPQs under path constraints. We focus on word constraints that can be viewed as tuple-generating dependencies (TGDs) of the form ∀x_1,x_2, ∃y⁻, a_1(x_1,y_1) ∧ ... ∧ a_i(y_{i-1},y_i) ∧ ... ∧ a_n(y_{n-1},x_2) ⟶ ∃z⁻, b_1(x_1,z_1) ∧ ... ∧ b_i(z_{i-1},z_i) ∧ ... ∧ b_m(z_{m-1},x_2). Such a constraint means that whenever two nodes in a graph are connected by a path labeled a_1 … a_n, there is also a path labeled b_1 … b_m that connects them. Rewrite systems offer an abstract view of these TGDs: the rewrite rule a_1 … a_n → b_1 … b_m represents the previous constraint. A set of constraints 𝒞 is then represented by a rewrite system R and, when dealing with possibly infinite databases, a path query p is contained in a path query q under the constraints 𝒞 iff p rewrites to q with R. Contrary to what has been claimed in the literature we show that, when restricting to finite databases only, there are cases where a path query p is contained in a path query q under the constraints 𝒞 while p does not rewrite to q with R. More generally, we study the finite controllability of the containment of RPQs under word constraints, that is when this containment problem on unrestricted databases does coincide with the finite case. We give an exact characterisation of the cases where this equivalence holds. We then deduce the undecidability of the containment problem in the finite case even when RPQs are restricted to word queries. We prove several properties related to finite controllability, and in particular that it is undecidable. We also exhibit some classes of word constraints that ensure the finite controllability and the decidability of the containment problem.
Cite as

Sylvain Salvati and Sophie Tison. Containment of Regular Path Queries Under Path Constraints. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 17:1-17:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{salvati_et_al:LIPIcs.ICDT.2024.17,
  author =	{Salvati, Sylvain and Tison, Sophie},
  title =	{{Containment of Regular Path Queries Under Path Constraints}},
  booktitle =	{27th International Conference on Database Theory (ICDT 2024)},
  pages =	{17:1--17:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-312-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{290},
  editor =	{Cormode, Graham and Shekelyan, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.17},
  URN =		{urn:nbn:de:0030-drops-197994},
  doi =		{10.4230/LIPIcs.ICDT.2024.17},
  annote =	{Keywords: Graph databases, rational path queries, query containment, TGDs, word constraints, rewrite systems, finite controllability, decision problems}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2024.18
Computing Data Distribution from Query Selectivities

Authors: Pankaj K. Agarwal, Rahul Raychaudhury, Stavros Sintos, and Jun Yang

Published in: LIPIcs, Volume 290, 27th International Conference on Database Theory (ICDT 2024)

Abstract
We are given a set 𝒵 = {(R_1,s_1), …, (R_n,s_n)}, where each R_i is a range in ℝ^d, such as rectangle or ball, and s_i ∈ [0,1] denotes its selectivity. The goal is to compute a small-size discrete data distribution 𝒟 = {(q₁,w₁),…, (q_m,w_m)}, where q_j ∈ ℝ^d and w_j ∈ [0,1] for each 1 ≤ j ≤ m, and ∑_{1≤j≤m} w_j = 1, such that 𝒟 is the most consistent with 𝒵, i.e., err_p(𝒟,𝒵) = 1/n ∑_{i = 1}ⁿ |s_i - ∑_{j=1}^m w_j⋅1(q_j ∈ R_i)|^p is minimized. In a database setting, 𝒵 corresponds to a workload of range queries over some table, together with their observed selectivities (i.e., fraction of tuples returned), and 𝒟 can be used as compact model for approximating the data distribution within the table without accessing the underlying contents. In this paper, we obtain both upper and lower bounds for this problem. In particular, we show that the problem of finding the best data distribution from selectivity queries is NP-complete. On the positive side, we describe a Monte Carlo algorithm that constructs, in time O((n+δ^{-d}) δ^{-2} polylog n), a discrete distribution 𝒟̃ of size O(δ^{-2}), such that err_p(𝒟̃,𝒵) ≤ min_𝒟 err_p(𝒟,𝒵)+δ (for p = 1,2,∞) where the minimum is taken over all discrete distributions. We also establish conditional lower bounds, which strongly indicate the infeasibility of relative approximations as well as removal of the exponential dependency on the dimension for additive approximations. This suggests that significant improvements to our algorithm are unlikely.
Cite as

Pankaj K. Agarwal, Rahul Raychaudhury, Stavros Sintos, and Jun Yang. Computing Data Distribution from Query Selectivities. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 18:1-18:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{agarwal_et_al:LIPIcs.ICDT.2024.18,
  author =	{Agarwal, Pankaj K. and Raychaudhury, Rahul and Sintos, Stavros and Yang, Jun},
  title =	{{Computing Data Distribution from Query Selectivities}},
  booktitle =	{27th International Conference on Database Theory (ICDT 2024)},
  pages =	{18:1--18:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-312-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{290},
  editor =	{Cormode, Graham and Shekelyan, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.18},
  URN =		{urn:nbn:de:0030-drops-198007},
  doi =		{10.4230/LIPIcs.ICDT.2024.18},
  annote =	{Keywords: selectivity queries, discrete distributions, Multiplicative Weights Update, eps-approximation, learnable functions, depth problem, arrangement}
}
Document
DOI: 10.4230/LIPIcs.STACS.2024.45
Circuit Equivalence in 2-Nilpotent Algebras

Authors: Piotr Kawałek, Michael Kompatscher, and Jacek Krzaczkowski

Published in: LIPIcs, Volume 289, 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)

Abstract
The circuit equivalence problem Ceqv(A) of a finite algebra A is the problem of deciding whether two circuits over A compute the same function or not. This problem not only generalises the equivalence problem for Boolean circuits, but is also of interest in universal algebra, as it models the problem of checking identities in A. In this paper we prove that Ceqv(A) ∈ 𝖯, if A is a finite 2-nilpotent algebra from a congruence modular variety.
Cite as

Piotr Kawałek, Michael Kompatscher, and Jacek Krzaczkowski. Circuit Equivalence in 2-Nilpotent Algebras. In 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 289, pp. 45:1-45:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{kawalek_et_al:LIPIcs.STACS.2024.45,
  author =	{Kawa{\l}ek, Piotr and Kompatscher, Michael and Krzaczkowski, Jacek},
  title =	{{Circuit Equivalence in 2-Nilpotent Algebras}},
  booktitle =	{41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)},
  pages =	{45:1--45:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-311-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{289},
  editor =	{Beyersdorff, Olaf and Kant\'{e}, Mamadou Moustapha and Kupferman, Orna and Lokshtanov, Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2024.45},
  URN =		{urn:nbn:de:0030-drops-197554},
  doi =		{10.4230/LIPIcs.STACS.2024.45},
  annote =	{Keywords: circuit equivalence, identity checking, nilpotent algebra}
}
Document
DOI: 10.4230/LIPIcs.STACS.2024.46
The Subpower Membership Problem of 2-Nilpotent Algebras

Authors: Michael Kompatscher

Published in: LIPIcs, Volume 289, 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)

Abstract
The subpower membership problem SMP(𝐀) of a finite algebraic structure 𝐀 asks whether a given partial function from Aⁿ to A can be interpolated by a term operation of 𝐀, or not. While this problem can be EXPTIME-complete in general, Willard asked whether it is always solvable in polynomial time if 𝐀 is a Mal'tsev algebra. In particular, this includes many important structures studied in abstract algebra, such as groups, quasigroups, rings, Boolean algebras. In this paper we give an affirmative answer to Willard’s question for a big class of 2-nilpotent Mal'tsev algebras. We furthermore develop tools that might be essential in answering the question for general nilpotent Mal'tsev algebras in the future.
Cite as

Michael Kompatscher. The Subpower Membership Problem of 2-Nilpotent Algebras. In 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 289, pp. 46:1-46:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{kompatscher:LIPIcs.STACS.2024.46,
  author =	{Kompatscher, Michael},
  title =	{{The Subpower Membership Problem of 2-Nilpotent Algebras}},
  booktitle =	{41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)},
  pages =	{46:1--46:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-311-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{289},
  editor =	{Beyersdorff, Olaf and Kant\'{e}, Mamadou Moustapha and Kupferman, Orna and Lokshtanov, Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2024.46},
  URN =		{urn:nbn:de:0030-drops-197562},
  doi =		{10.4230/LIPIcs.STACS.2024.46},
  annote =	{Keywords: subpower membership problem, Mal'tsev algebra, compact representation, nilpotence, clonoids}
}
Document
DOI: 10.4230/OASIcs.PARMA-DITAM.2024.5
Embedded Multi-Core Code Generation with Cross-Layer Parallelization

Authors: Oliver Oey, Michael Huebner, Timo Stripf, and Juergen Becker

Published in: OASIcs, Volume 116, 15th Workshop on Parallel Programming and Run-Time Management Techniques for Many-Core Architectures and 13th Workshop on Design Tools and Architectures for Multicore Embedded Computing Platforms (PARMA-DITAM 2024)

Abstract
In this paper, we present a method for optimizing C code for embedded multi-core systems using cross-layer parallelization. The method has two phases. The first is to develop the algorithm without any optimization for the target platform. Then, the second step is to optimize and parallelize the code across four defined layers which are the algorithm, code, task, and data layers, for efficient execution on the target hardware. Each layer is focused on selected hardware characteristics. By using an iterative approach, individual kernels and composite algorithms can be very well adapted to execution on the hardware without further adaptation of the algorithm itself. The realization of this cross-layer parallelization consists of algorithm recognition, code transformations, task distribution, and insertion of synchronization and communication statements. The method is evaluated first on a common kernel and then on a sample image processing algorithm to showcase the benefits of the approach. Compared to other methods that only rely on two or three of these layers, 20 to 30 % of additional performance gain can be achieved.
Cite as

Oliver Oey, Michael Huebner, Timo Stripf, and Juergen Becker. Embedded Multi-Core Code Generation with Cross-Layer Parallelization. In 15th Workshop on Parallel Programming and Run-Time Management Techniques for Many-Core Architectures and 13th Workshop on Design Tools and Architectures for Multicore Embedded Computing Platforms (PARMA-DITAM 2024). Open Access Series in Informatics (OASIcs), Volume 116, pp. 5:1-5:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{oey_et_al:OASIcs.PARMA-DITAM.2024.5,
  author =	{Oey, Oliver and Huebner, Michael and Stripf, Timo and Becker, Juergen},
  title =	{{Embedded Multi-Core Code Generation with Cross-Layer Parallelization}},
  booktitle =	{15th Workshop on Parallel Programming and Run-Time Management Techniques for Many-Core Architectures and 13th Workshop on Design Tools and Architectures for Multicore Embedded Computing Platforms (PARMA-DITAM 2024)},
  pages =	{5:1--5:13},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-307-2},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{116},
  editor =	{Bispo, Jo\~{a}o and Xydis, Sotirios and Curzel, Serena and Sousa, Lu{\'\i}s Miguel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.PARMA-DITAM.2024.5},
  URN =		{urn:nbn:de:0030-drops-196990},
  doi =		{10.4230/OASIcs.PARMA-DITAM.2024.5},
  annote =	{Keywords: Parallelization, multi-core Processors, model-based Development, Code Generation}
}
Document
DOI: 10.4230/LIPIcs.CSL.2024.32
Characterising and Verifying the Core in Concurrent Multi-Player Mean-Payoff Games

Authors: Julian Gutierrez, Anthony W. Lin, Muhammad Najib, Thomas Steeples, and Michael Wooldridge

Published in: LIPIcs, Volume 288, 32nd EACSL Annual Conference on Computer Science Logic (CSL 2024)

Abstract
Concurrent multi-player mean-payoff games are important models for systems of agents with individual, non-dichotomous preferences. Whilst these games have been extensively studied in terms of their equilibria in non-cooperative settings, this paper explores an alternative solution concept: the core from cooperative game theory. This concept is particularly relevant for cooperative AI systems, as it enables the modelling of cooperation among agents, even when their goals are not fully aligned. Our contribution is twofold. First, we provide a characterisation of the core using discrete geometry techniques and establish a necessary and sufficient condition for its non-emptiness. We then use the characterisation to prove the existence of polynomial witnesses in the core. Second, we use the existence of such witnesses to solve key decision problems in rational verification and provide tight complexity bounds for the problem of checking whether some/every equilibrium in a game satisfies a given LTL or GR(1) specification. Our approach is general and can be adapted to handle other specifications expressed in various fragments of LTL without incurring additional computational costs.
Cite as

Julian Gutierrez, Anthony W. Lin, Muhammad Najib, Thomas Steeples, and Michael Wooldridge. Characterising and Verifying the Core in Concurrent Multi-Player Mean-Payoff Games. In 32nd EACSL Annual Conference on Computer Science Logic (CSL 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 288, pp. 32:1-32:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{gutierrez_et_al:LIPIcs.CSL.2024.32,
  author =	{Gutierrez, Julian and Lin, Anthony W. and Najib, Muhammad and Steeples, Thomas and Wooldridge, Michael},
  title =	{{Characterising and Verifying the Core in Concurrent Multi-Player Mean-Payoff Games}},
  booktitle =	{32nd EACSL Annual Conference on Computer Science Logic (CSL 2024)},
  pages =	{32:1--32:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-310-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{288},
  editor =	{Murano, Aniello and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2024.32},
  URN =		{urn:nbn:de:0030-drops-196752},
  doi =		{10.4230/LIPIcs.CSL.2024.32},
  annote =	{Keywords: Concurrent games, multi-agent systems, temporal logic, game theory}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2024.42
Time- and Communication-Efficient Overlay Network Construction via Gossip

Authors: Fabien Dufoulon, Michael Moorman, William K. Moses Jr., and Gopal Pandurangan

Published in: LIPIcs, Volume 287, 15th Innovations in Theoretical Computer Science Conference (ITCS 2024)

Abstract
We focus on the well-studied problem of distributed overlay network construction. We consider a synchronous gossip-based communication model where in each round a node can send a message of small size to another node whose identifier it knows. The network is assumed to be reconfigurable, i.e., a node can add new connections (edges) to other nodes whose identifier it knows or drop existing connections. Each node initially has only knowledge of its own identifier and the identifiers of its neighbors. The overlay construction problem is, given an arbitrary (connected) graph, to reconfigure it to obtain a bounded-degree expander graph as efficiently as possible. The overlay construction problem is relevant to building real-world peer-to-peer network topologies that have desirable properties such as low diameter, high conductance, robustness to adversarial deletions, etc. Our main result is that we show that starting from any arbitrary (connected) graph G on n nodes and m edges, we can construct an overlay network that is a constant-degree expander in polylog rounds using only Õ(n) messages. Our time and message bounds are both essentially optimal (up to polylogarithmic factors). Our distributed overlay construction protocol is very lightweight as it uses gossip (each node communicates with only one neighbor in each round) and also scalable as it uses only Õ(n) messages, which is sublinear in m (even when m is moderately dense). To the best of our knowledge, this is the first result that achieves overlay network construction in polylog rounds and o(m) messages. Our protocol uses graph sketches in a novel way to construct an expander overlay that is both time and communication efficient. A consequence of our overlay construction protocol is that distributed computation can be performed very efficiently in this model. In particular, a wide range of fundamental tasks such as broadcast, leader election, and minimum spanning tree (MST) construction can be accomplished in polylog rounds and Õ(n) message complexity in any graph.
Cite as

Fabien Dufoulon, Michael Moorman, William K. Moses Jr., and Gopal Pandurangan. Time- and Communication-Efficient Overlay Network Construction via Gossip. In 15th Innovations in Theoretical Computer Science Conference (ITCS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 287, pp. 42:1-42:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{dufoulon_et_al:LIPIcs.ITCS.2024.42,
  author =	{Dufoulon, Fabien and Moorman, Michael and Moses Jr., William K. and Pandurangan, Gopal},
  title =	{{Time- and Communication-Efficient Overlay Network Construction via Gossip}},
  booktitle =	{15th Innovations in Theoretical Computer Science Conference (ITCS 2024)},
  pages =	{42:1--42:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-309-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{287},
  editor =	{Guruswami, Venkatesan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2024.42},
  URN =		{urn:nbn:de:0030-drops-195700},
  doi =		{10.4230/LIPIcs.ITCS.2024.42},
  annote =	{Keywords: Peer-to-Peer Networks, Overlay Construction Protocol, Gossip, Expanders, Sublinear Bounds}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2024.83
On the Size Overhead of Pairwise Spanners

Authors: Ofer Neiman and Idan Shabat

Published in: LIPIcs, Volume 287, 15th Innovations in Theoretical Computer Science Conference (ITCS 2024)

Abstract
Given an undirected possibly weighted n-vertex graph G = (V,E) and a set 𝒫 ⊆ V² of pairs, a subgraph S = (V,E') is called a P-pairwise α-spanner of G, if for every pair (u,v) ∈ 𝒫 we have d_S(u,v) ≤ α⋅ d_G(u,v). The parameter α is called the stretch of the spanner, and its size overhead is define as |E'|/|P|. A surprising connection was recently discussed between the additive stretch of (1+ε,β)-spanners, to the hopbound of (1+ε,β)-hopsets. A long sequence of works showed that if the spanner/hopset has size ≈ n^{1+1/k} for some parameter k ≥ 1, then β≈(1/ε)^{log k}. In this paper we establish a new connection to the size overhead of pairwise spanners. In particular, we show that if |P|≈ n^{1+1/k}, then a P-pairwise (1+ε)-spanner must have size at least β⋅ |P| with β≈(1/ε)^{log k} (a near matching upper bound was recently shown in [Michael Elkin and Idan Shabat, 2023]). That is, the size overhead of pairwise spanners has similar bounds to the hopbound of hopsets, and to the additive stretch of spanners. We also extend the connection between pairwise spanners and hopsets to the large stretch regime, by showing nearly matching upper and lower bounds for P-pairwise α-spanners. In particular, we show that if |P|≈ n^{1+1/k}, then the size overhead is β≈k/α. A source-wise spanner is a special type of pairwise spanner, for which P = A×V for some A ⊆ V. A prioritized spanner is given also a ranking of the vertices V = (v₁,… ,v_n), and is required to provide improved stretch for pairs containing higher ranked vertices. By using a sequence of reductions: from pairwise spanners to source-wise spanners to prioritized spanners, we improve on the state-of-the-art results for source-wise and prioritized spanners. Since our spanners can be equipped with a path-reporting mechanism, we also substantially improve the known bounds for path-reporting prioritized distance oracles. Specifically, we provide a path-reporting distance oracle, with size O(n⋅(log log n)²), that has a constant stretch for any query that contains a vertex ranked among the first n^{1-δ} vertices (for any constant δ > 0). Such a result was known before only for non-path-reporting distance oracles.
Cite as

Ofer Neiman and Idan Shabat. On the Size Overhead of Pairwise Spanners. In 15th Innovations in Theoretical Computer Science Conference (ITCS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 287, pp. 83:1-83:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{neiman_et_al:LIPIcs.ITCS.2024.83,
  author =	{Neiman, Ofer and Shabat, Idan},
  title =	{{On the Size Overhead of Pairwise Spanners}},
  booktitle =	{15th Innovations in Theoretical Computer Science Conference (ITCS 2024)},
  pages =	{83:1--83:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-309-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{287},
  editor =	{Guruswami, Venkatesan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2024.83},
  URN =		{urn:nbn:de:0030-drops-196110},
  doi =		{10.4230/LIPIcs.ITCS.2024.83},
  annote =	{Keywords: Graph Algorithms, Shortest Paths, Spanners}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2023.2
Quantum Distributed Computing: Potential and Limitations (Invited Talk)

Authors: François Le Gall

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

Abstract
The subject of this talk is quantum distributed computing, i.e., distributed computing where the processors of the network can exchange quantum messages. In the first part of the talk I survey recent results [Taisuke Izumi and François Le Gall, 2019; Taisuke Izumi et al., 2020; François Le Gall and Frédéric Magniez, 2018; François Le Gall et al., 2019; Xudong Wu and Penghui Yao, 2022] and some older results [Michael Ben-Or and Avinatan Hassidim, 2005; Seiichiro Tani et al., 2012] that show the potential of quantum distributed algorithms. In the second part I present our recent work [Xavier Coiteux-Roy et al., 2023] showing the limitations of quantum distributed algorithms for approximate graph coloring. Finally, I mention interesting and important open questions in quantum distributed computing.
Cite as

François Le Gall. Quantum Distributed Computing: Potential and Limitations (Invited Talk). In 27th International Conference on Principles of Distributed Systems (OPODIS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 286, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{legall:LIPIcs.OPODIS.2023.2,
  author =	{Le Gall, Fran\c{c}ois},
  title =	{{Quantum Distributed Computing: Potential and Limitations}},
  booktitle =	{27th International Conference on Principles of Distributed Systems (OPODIS 2023)},
  pages =	{2:1--2:1},
  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-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2023.2},
  URN =		{urn:nbn:de:0030-drops-194925},
  doi =		{10.4230/LIPIcs.OPODIS.2023.2},
  annote =	{Keywords: Quantum computing, distributed algorithms, CONGEST model, LOCAL model}
}
Document
Survey
DOI: 10.4230/TGDK.1.1.12
Structural Summarization of Semantic Graphs Using Quotients

Authors: Ansgar Scherp, David Richerby, Till Blume, Michael Cochez, and Jannik Rau

Published in: TGDK, Volume 1, Issue 1 (2023): Special Issue on Trends in Graph Data and Knowledge. Transactions on Graph Data and Knowledge, Volume 1, Issue 1

Abstract
Graph summarization is the process of computing a compact version of an input graph while preserving chosen features of its structure. We consider semantic graphs where the features include edge labels and label sets associated with a vertex. Graph summaries are typically much smaller than the original graph. Applications that depend on the preserved features can perform their tasks on the summary, but much faster or with less memory overhead, while producing the same outcome as if they were applied on the original graph. In this survey, we focus on structural summaries based on quotients that organize vertices in equivalence classes of shared features. Structural summaries are particularly popular for semantic graphs and have the advantage of defining a precise graph-based output. We consider approaches and algorithms for both static and temporal graphs. A common example of quotient-based structural summaries is bisimulation, and we discuss this in detail. While there exist other surveys on graph summarization, to the best of our knowledge, we are the first to bring in a focused discussion on quotients, bisimulation, and their relation. Furthermore, structural summarization naturally connects well with formal logic due to the discrete structures considered. We complete the survey with a brief description of approaches beyond structural summaries.
Cite as

Ansgar Scherp, David Richerby, Till Blume, Michael Cochez, and Jannik Rau. Structural Summarization of Semantic Graphs Using Quotients. In Special Issue on Trends in Graph Data and Knowledge. Transactions on Graph Data and Knowledge (TGDK), Volume 1, Issue 1, pp. 12:1-12:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

Copy BibTex To Clipboard

@Article{scherp_et_al:TGDK.1.1.12,
  author =	{Scherp, Ansgar and Richerby, David and Blume, Till and Cochez, Michael and Rau, Jannik},
  title =	{{Structural Summarization of Semantic Graphs Using Quotients}},
  journal =	{Transactions on Graph Data and Knowledge},
  pages =	{12:1--12:25},
  ISSN =	{2942-7517},
  year =	{2023},
  volume =	{1},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/TGDK.1.1.12},
  URN =		{urn:nbn:de:0030-drops-194862},
  doi =		{10.4230/TGDK.1.1.12},
  annote =	{Keywords: graph summarization, quotients, stratified bisimulation}
}
  • Refine by Author
  • 13 Lampis, Michael
  • 8 Neiman, Ofer
  • 7 Hoffmann, Michael
  • 6 Elkin, Michael
  • 5 Bender, Michael A.
  • Show More...

  • Refine by Classification
  • 25 Theory of computation → Computational geometry
  • 18 Mathematics of computing → Graph algorithms
  • 18 Theory of computation → Design and analysis of algorithms
  • 14 Theory of computation → Graph algorithms analysis
  • 12 Theory of computation → Parameterized complexity and exact algorithms
  • Show More...

  • Refine by Keyword
  • 8 Treewidth
  • 7 Approximation Algorithms
  • 6 lower bounds
  • 5 Graph drawing
  • 5 graph algorithms
  • Show More...

  • Refine by Type
  • 463 document

  • Refine by Publication Year
  • 68 2016
  • 58 2019
  • 50 2022
  • 32 2021
  • 31 2023
  • Show More...

Questions / Remarks / Feedback
X

Feedback for Dagstuhl Publishing


Thanks for your feedback!

Feedback submitted

Could not send message

Please try again later or send an E-mail
© 2023-2024 Schloss Dagstuhl – LZI GmbH Imprint Privacy Contact