6 Search Results for "Keppeler, Jens"

Document
DOI: 10.4230/LIPIcs.MFCS.2023.80
Dynamic Constant Time Parallel Graph Algorithms with Sub-Linear Work

Authors: Jonas Schmidt and Thomas Schwentick

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

Abstract
The paper proposes dynamic parallel algorithms for connectivity and bipartiteness of undirected graphs that require constant time and 𝒪(n^{1/2+ε}) work on the CRCW PRAM model. The work of these algorithms almost matches the work of the 𝒪(log n) time algorithm for connectivity by Kopelowitz et al. (2018) on the EREW PRAM model and the time of the sequential algorithm for bipartiteness by Eppstein et al. (1997). In particular, we show that the sparsification technique, which has been used in both mentioned papers, can in principle also be used for constant time algorithms in the CRCW PRAM model, despite the logarithmic depth of sparsification trees.
Cite as

Jonas Schmidt and Thomas Schwentick. Dynamic Constant Time Parallel Graph Algorithms with Sub-Linear Work. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 80:1-80:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

Copy BibTex To Clipboard

@InProceedings{schmidt_et_al:LIPIcs.MFCS.2023.80,
  author =	{Schmidt, Jonas and Schwentick, Thomas},
  title =	{{Dynamic Constant Time Parallel Graph Algorithms with Sub-Linear Work}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{80:1--80:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-292-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{272},
  editor =	{Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.80},
  URN =		{urn:nbn:de:0030-drops-186140},
  doi =		{10.4230/LIPIcs.MFCS.2023.80},
  annote =	{Keywords: Dynamic parallel algorithms, Undirected connectivity, Bipartiteness}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2023.81
On the Work of Dynamic Constant-Time Parallel Algorithms for Regular Tree Languages and Context-Free Languages

Authors: Jonas Schmidt, Thomas Schwentick, and Jennifer Todtenhoefer

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

Abstract
Previous work on Dynamic Complexity has established that there exist dynamic constant-time parallel algorithms for regular tree languages and context-free languages under label or symbol changes. However, these algorithms were not developed with the goal to minimise work (or, equivalently, the number of processors). In fact, their inspection yields the work bounds 𝒪(n²) and 𝒪(n⁷) per change operation, respectively. In this paper, dynamic algorithms for regular tree languages are proposed that generalise the previous algorithms in that they allow unbounded node rank and leaf insertions, while improving the work bound from 𝒪(n²) to 𝒪(n^ε), for arbitrary ε > 0. For context-free languages, algorithms with better work bounds (compared with 𝒪(n⁷)) for restricted classes are proposed: for every ε > 0 there are such algorithms for deterministic context-free languages with work bound 𝒪(n^{3+ε}) and for visibly pushdown languages with work bound 𝒪(n^{2+ε}).
Cite as

Jonas Schmidt, Thomas Schwentick, and Jennifer Todtenhoefer. On the Work of Dynamic Constant-Time Parallel Algorithms for Regular Tree Languages and Context-Free Languages. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 81:1-81:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

Copy BibTex To Clipboard

@InProceedings{schmidt_et_al:LIPIcs.MFCS.2023.81,
  author =	{Schmidt, Jonas and Schwentick, Thomas and Todtenhoefer, Jennifer},
  title =	{{On the Work of Dynamic Constant-Time Parallel Algorithms for Regular Tree Languages and Context-Free Languages}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{81:1--81:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-292-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{272},
  editor =	{Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.81},
  URN =		{urn:nbn:de:0030-drops-186152},
  doi =		{10.4230/LIPIcs.MFCS.2023.81},
  annote =	{Keywords: Dynamic complexity, work, parallel constant time}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2023.16
Work-Efficient Query Evaluation with PRAMs

Authors: Jens Keppeler, Thomas Schwentick, and Christopher Spinrath

Published in: LIPIcs, Volume 255, 26th International Conference on Database Theory (ICDT 2023)

Abstract
The paper studies query evaluation in parallel constant time in the PRAM model. While it is well-known that all relational algebra queries can be evaluated in constant time on an appropriate CRCW-PRAM, this paper is interested in the efficiency of evaluation algorithms, that is, in the number of processors or, asymptotically equivalent, in the work. Naive evaluation in the parallel setting results in huge (polynomial) bounds on the work of such algorithms and in presentations of the result sets that can be extremely scattered in memory. The paper first discusses some obstacles for constant time PRAM query evaluation. It presents algorithms for relational operators that are considerably more efficient than the naive approaches. Further it explores three settings, in which efficient sequential query evaluation algorithms exist: acyclic queries, semi-join algebra queries, and join queries - the latter in the worst-case optimal framework. Under natural assumptions on the representation of the database, the work of the given algorithms matches the best sequential algorithms in the case of semi-join queries, and it comes close in the other two settings. An important tool is the compaction technique from Hagerup (1992).
Cite as

Jens Keppeler, Thomas Schwentick, and Christopher Spinrath. Work-Efficient Query Evaluation with PRAMs. In 26th International Conference on Database Theory (ICDT 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 255, pp. 16:1-16:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

Copy BibTex To Clipboard

@InProceedings{keppeler_et_al:LIPIcs.ICDT.2023.16,
  author =	{Keppeler, Jens and Schwentick, Thomas and Spinrath, Christopher},
  title =	{{Work-Efficient Query Evaluation with PRAMs}},
  booktitle =	{26th International Conference on Database Theory (ICDT 2023)},
  pages =	{16:1--16:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-270-9},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{255},
  editor =	{Geerts, Floris and Vandevoort, Brecht},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2023.16},
  URN =		{urn:nbn:de:0030-drops-177589},
  doi =		{10.4230/LIPIcs.ICDT.2023.16},
  annote =	{Keywords: PRAM, query evaluation, work-efficient, parallel, acyclic queries, free-connex queries}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2022.8
Rewriting with Acyclic Queries: Mind Your Head

Authors: Gaetano Geck, Jens Keppeler, Thomas Schwentick, and Christopher Spinrath

Published in: LIPIcs, Volume 220, 25th International Conference on Database Theory (ICDT 2022)

Abstract
The paper studies the rewriting problem, that is, the decision problem whether, for a given conjunctive query Q and a set 𝒱 of views, there is a conjunctive query Q' over 𝒱 that is equivalent to Q, for cases where the query, the views, and/or the desired rewriting are acyclic or even more restricted. It shows that, if Q itself is acyclic, an acyclic rewriting exists if there is any rewriting. An analogous statement also holds for free-connex acyclic, hierarchical, and q-hierarchical queries. Regarding the complexity of the rewriting problem, the paper identifies a border between tractable and (presumably) intractable variants of the rewriting problem: for schemas of bounded arity, the acyclic rewriting problem is NP-hard, even if both Q and the views in 𝒱 are acyclic or hierarchical. However, it becomes tractable, if the views are free-connex acyclic (i.e., in a nutshell, their body is (i) acyclic and (ii) remains acyclic if their head is added as an additional atom).
Cite as

Gaetano Geck, Jens Keppeler, Thomas Schwentick, and Christopher Spinrath. Rewriting with Acyclic Queries: Mind Your Head. In 25th International Conference on Database Theory (ICDT 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 220, pp. 8:1-8:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

Copy BibTex To Clipboard

@InProceedings{geck_et_al:LIPIcs.ICDT.2022.8,
  author =	{Geck, Gaetano and Keppeler, Jens and Schwentick, Thomas and Spinrath, Christopher},
  title =	{{Rewriting with Acyclic Queries: Mind Your Head}},
  booktitle =	{25th International Conference on Database Theory (ICDT 2022)},
  pages =	{8:1--8:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-223-5},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{220},
  editor =	{Olteanu, Dan and Vortmeier, Nils},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2022.8},
  URN =		{urn:nbn:de:0030-drops-158829},
  doi =		{10.4230/LIPIcs.ICDT.2022.8},
  annote =	{Keywords: rewriting, acyclic rewriting, acyclic conjunctive queries, free-connex queries, hierarchical queries, NP-hardness}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2018.8
Answering UCQs under Updates and in the Presence of Integrity Constraints

Authors: Christoph Berkholz, Jens Keppeler, and Nicole Schweikardt

Published in: LIPIcs, Volume 98, 21st International Conference on Database Theory (ICDT 2018)

Abstract
We investigate the query evaluation problem for fixed queries over fully dynamic databases where tuples can be inserted or deleted. The task is to design a dynamic data structure that can immediately report the new result of a fixed query after every database update. We consider unions of conjunctive queries (UCQs) and focus on the query evaluation tasks testing (decide whether an input tuple belongs to the query result), enumeration (enumerate, without repetition, all tuples in the query result), and counting (output the number of tuples in the query result). We identify three increasingly restrictive classes of UCQs which we call t-hierarchical, q-hierarchical, and exhaustively q-hierarchical UCQs. Our main results provide the following dichotomies: If the query's homomorphic core is t-hierarchical (q-hierarchical, exhaustively q-hierarchical), then the testing (enumeration, counting) problem can be solved with constant update time and constant testing time (delay, counting time). Otherwise, it cannot be solved with sublinear update time and sublinear testing time (delay, counting time), unless the OV-conjecture and/or the OMv-conjecture fails. We also study the complexity of query evaluation in the dynamic setting in the presence of integrity constraints, and we obtain similar dichotomy results for the special case of small domain constraints (i.e., constraints which state that all values in a particular column of a relation belong to a fixed domain of constant size).
Cite as

Christoph Berkholz, Jens Keppeler, and Nicole Schweikardt. Answering UCQs under Updates and in the Presence of Integrity Constraints. In 21st International Conference on Database Theory (ICDT 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 98, pp. 8:1-8:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

Copy BibTex To Clipboard

@InProceedings{berkholz_et_al:LIPIcs.ICDT.2018.8,
  author =	{Berkholz, Christoph and Keppeler, Jens and Schweikardt, Nicole},
  title =	{{Answering UCQs under Updates and in the Presence of Integrity Constraints}},
  booktitle =	{21st International Conference on Database Theory (ICDT 2018)},
  pages =	{8:1--8:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-063-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{98},
  editor =	{Kimelfeld, Benny and Amsterdamer, Yael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2018.8},
  URN =		{urn:nbn:de:0030-drops-85990},
  doi =		{10.4230/LIPIcs.ICDT.2018.8},
  annote =	{Keywords: dynamic query evaluation, union of conjunctive queries, constant-delay enumeration, counting problem, testing}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2017.8
Answering FO+MOD Queries Under Updates on Bounded Degree Databases

Authors: Christoph Berkholz, Jens Keppeler, and Nicole Schweikardt

Published in: LIPIcs, Volume 68, 20th International Conference on Database Theory (ICDT 2017)

Abstract
We investigate the query evaluation problem for fixed queries over fully dynamic databases, where tuples can be inserted or deleted. The task is to design a dynamic algorithm that immediately reports the new result of a fixed query after every database update. We consider queries in first-order logic (FO) and its extension with modulo-counting quantifiers (FO+MOD), and show that they can be efficiently evaluated under updates, provided that the dynamic database does not exceed a certain degree bound. In particular, we construct a data structure that allows to answer a Boolean FO+MOD query and to compute the size of the query result within constant time after every database update. Furthermore, after every update we are able to immediately enumerate the new query result with constant delay between the output tuples. The time needed to build the data structure is linear in the size of the database. Our results extend earlier work on the evaluation of first-order queries on static databases of bounded degree and rely on an effective Hanf normal form for FO+MOD recently obtained by [Heimberg, Kuske, and Schweikardt, LICS, 2016].
Cite as

Christoph Berkholz, Jens Keppeler, and Nicole Schweikardt. Answering FO+MOD Queries Under Updates on Bounded Degree Databases. In 20th International Conference on Database Theory (ICDT 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 68, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

Copy BibTex To Clipboard

@InProceedings{berkholz_et_al:LIPIcs.ICDT.2017.8,
  author =	{Berkholz, Christoph and Keppeler, Jens and Schweikardt, Nicole},
  title =	{{Answering FO+MOD Queries Under Updates on Bounded Degree Databases}},
  booktitle =	{20th International Conference on Database Theory (ICDT 2017)},
  pages =	{8:1--8:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-024-8},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{68},
  editor =	{Benedikt, Michael and Orsi, Giorgio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2017.8},
  URN =		{urn:nbn:de:0030-drops-70535},
  doi =		{10.4230/LIPIcs.ICDT.2017.8},
  annote =	{Keywords: dynamic databases, query enumeration, counting problem, first-order logic with modulo-counting quantifiers, Hanf locality}
}
  • Refine by Author
  • 4 Keppeler, Jens
  • 4 Schwentick, Thomas
  • 2 Berkholz, Christoph
  • 2 Schmidt, Jonas
  • 2 Schweikardt, Nicole
  • Show More...

  • Refine by Classification
  • 2 Theory of computation → Database query processing and optimization (theory)
  • 2 Theory of computation → Parallel algorithms
  • 1 Theory of computation → Data integration
  • 1 Theory of computation → Dynamic graph algorithms
  • 1 Theory of computation → Formal languages and automata theory
  • Show More...

  • Refine by Keyword
  • 2 counting problem
  • 2 free-connex queries
  • 1 Bipartiteness
  • 1 Dynamic complexity
  • 1 Dynamic parallel algorithms
  • Show More...

  • Refine by Type
  • 6 document

  • Refine by Publication Year
  • 3 2023
  • 1 2017
  • 1 2018
  • 1 2022

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