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Documents authored by Kara, Ahmet

Document
DOI: 10.4230/LIPIcs.ICDT.2023.17
Conjunctive Queries with Free Access Patterns Under Updates

Authors: Ahmet Kara, Milos Nikolic, Dan Olteanu, and Haozhe Zhang

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

Abstract
We study the problem of answering conjunctive queries with free access patterns under updates. A free access pattern is a partition of the free variables of the query into input and output. The query returns tuples over the output variables given a tuple of values over the input variables. We introduce a fully dynamic evaluation approach for such queries. We also give a syntactic characterisation of those queries that admit constant time per single-tuple update and whose output tuples can be enumerated with constant delay given an input tuple. Finally, we chart the complexity trade-off between the preprocessing time, update time and enumeration delay for such queries. For a class of queries, our approach achieves optimal, albeit non-constant, update time and delay. Their optimality is predicated on the Online Matrix-Vector Multiplication conjecture. Our results recover prior work on the dynamic evaluation of conjunctive queries without access patterns.
Cite as

Ahmet Kara, Milos Nikolic, Dan Olteanu, and Haozhe Zhang. Conjunctive Queries with Free Access Patterns Under Updates. In 26th International Conference on Database Theory (ICDT 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 255, pp. 17:1-17:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{kara_et_al:LIPIcs.ICDT.2023.17,
  author =	{Kara, Ahmet and Nikolic, Milos and Olteanu, Dan and Zhang, Haozhe},
  title =	{{Conjunctive Queries with Free Access Patterns Under Updates}},
  booktitle =	{26th International Conference on Database Theory (ICDT 2023)},
  pages =	{17:1--17:20},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2023.17},
  URN =		{urn:nbn:de:0030-drops-177599},
  doi =		{10.4230/LIPIcs.ICDT.2023.17},
  annote =	{Keywords: fully dynamic algorithm, enumeration delay, complexity trade-off, dichotomy}
}
Document
DOI: 10.4230/LIPIcs.CSL.2023.29
Evaluation Trade-Offs for Acyclic Conjunctive Queries

Authors: Ahmet Kara, Milos Nikolic, Dan Olteanu, and Haozhe Zhang

Published in: LIPIcs, Volume 252, 31st EACSL Annual Conference on Computer Science Logic (CSL 2023)

Abstract
We consider the evaluation of acyclic conjunctive queries, where the evaluation time is decomposed into preprocessing time and enumeration delay. In a seminal paper at CSL'07, Bagan, Durand, and Grandjean showed that acyclic queries can be evaluated with linear preprocessing time and linear enumeration delay. If the query is free-connex, the enumeration delay becomes constant. Further prior work showed that constant enumeration delay can be achieved for arbitrary acyclic conjunctive queries at the expense of a preprocessing time that is characterised by the fractional hypertree width. We introduce an approach that exposes a trade-off between preprocessing time and enumeration delay for acyclic conjunctive queries. The aforementioned prior works represent extremes in this trade-off space. Yet our approach also allows for the enumeration delay and the preprocessing time between these extremes, in particular the delay may lie between constant and linear time. Our approach decomposes the given query into subqueries and achieves for each subquery a trade-off that depends on a parameter controlling the times for preprocessing and enumeration. The complexity of the query is given by the Pareto optimal points of a bi-objective optimisation program whose inputs are possible query decompositions and parameter values.
Cite as

Ahmet Kara, Milos Nikolic, Dan Olteanu, and Haozhe Zhang. Evaluation Trade-Offs for Acyclic Conjunctive Queries. In 31st EACSL Annual Conference on Computer Science Logic (CSL 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 252, pp. 29:1-29:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{kara_et_al:LIPIcs.CSL.2023.29,
  author =	{Kara, Ahmet and Nikolic, Milos and Olteanu, Dan and Zhang, Haozhe},
  title =	{{Evaluation Trade-Offs for Acyclic Conjunctive Queries}},
  booktitle =	{31st EACSL Annual Conference on Computer Science Logic (CSL 2023)},
  pages =	{29:1--29:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-264-8},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{252},
  editor =	{Klin, Bartek and Pimentel, Elaine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2023.29},
  URN =		{urn:nbn:de:0030-drops-174907},
  doi =		{10.4230/LIPIcs.CSL.2023.29},
  annote =	{Keywords: acyclic queries, query evaluation, enumeration delay}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2019.4
Counting Triangles under Updates in Worst-Case Optimal Time

Authors: Ahmet Kara, Hung Q. Ngo, Milos Nikolic, Dan Olteanu, and Haozhe Zhang

Published in: LIPIcs, Volume 127, 22nd International Conference on Database Theory (ICDT 2019)

Abstract
We consider the problem of incrementally maintaining the triangle count query under single-tuple updates to the input relations. We introduce an approach that exhibits a space-time tradeoff such that the space-time product is quadratic in the size of the input database and the update time can be as low as the square root of this size. This lowest update time is worst-case optimal conditioned on the Online Matrix-Vector Multiplication conjecture. The classical and factorized incremental view maintenance approaches are recovered as special cases of our approach within the space-time tradeoff. In particular, they require linear-time maintenance under updates, which is suboptimal. Our approach can also count all triangles in a static database in the worst-case optimal time needed for enumerating them.
Cite as

Ahmet Kara, Hung Q. Ngo, Milos Nikolic, Dan Olteanu, and Haozhe Zhang. Counting Triangles under Updates in Worst-Case Optimal Time. In 22nd International Conference on Database Theory (ICDT 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 127, pp. 4:1-4:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{kara_et_al:LIPIcs.ICDT.2019.4,
  author =	{Kara, Ahmet and Ngo, Hung Q. and Nikolic, Milos and Olteanu, Dan and Zhang, Haozhe},
  title =	{{Counting Triangles under Updates in Worst-Case Optimal Time}},
  booktitle =	{22nd International Conference on Database Theory (ICDT 2019)},
  pages =	{4:1--4:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-101-6},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{127},
  editor =	{Barcelo, Pablo and Calautti, Marco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2019.4},
  URN =		{urn:nbn:de:0030-drops-103068},
  doi =		{10.4230/LIPIcs.ICDT.2019.4},
  annote =	{Keywords: incremental view maintenance, amortized analysis, data skew}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2018.16
Covers of Query Results

Authors: Ahmet Kara and Dan Olteanu

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

Abstract
We introduce succinct lossless representations of query results called covers. They are subsets of the query results that correspond to minimal edge covers in the hypergraphs of these results. We first study covers whose structures are given by fractional hypertree decompositions of join queries. For any decomposition of a query, we give asymptotically tight size bounds for the covers of the query result over that decomposition and show that such covers can be computed in worst-case optimal time up to a logarithmic factor in the database size. For acyclic join queries, we can compute covers compositionally using query plans with a new operator called cover-join. The tuples in the query result can be enumerated from any of its covers with linearithmic pre-computation time and constant delay. We then generalize covers from joins to functional aggregate queries that express a host of computational problems such as aggregate-join queries, in-database optimization, matrix chain multiplication, and inference in probabilistic graphical models.
Cite as

Ahmet Kara and Dan Olteanu. Covers of Query Results. In 21st International Conference on Database Theory (ICDT 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 98, pp. 16:1-16:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{kara_et_al:LIPIcs.ICDT.2018.16,
  author =	{Kara, Ahmet and Olteanu, Dan},
  title =	{{Covers of Query Results}},
  booktitle =	{21st International Conference on Database Theory (ICDT 2018)},
  pages =	{16:1--16:22},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2018.16},
  URN =		{urn:nbn:de:0030-drops-86100},
  doi =		{10.4230/LIPIcs.ICDT.2018.16},
  annote =	{Keywords: factorized database, fractional hypertree decomposition, functional aggregate query, minimal edge cover, query plan}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2014.653
Verification of Dynamic Register Automata

Authors: Parosh Aziz Abdulla, Mohamed Faouzi Atig, Ahmet Kara, and Othmane Rezine

Published in: LIPIcs, Volume 29, 34th International Conference on Foundation of Software Technology and Theoretical Computer Science (FSTTCS 2014)

Abstract
We consider the verification problem for Dynamic Register Automata (DRA). DRA extend classical register automata by process creation. In this setting, each process is equipped with a finite set of registers in which the process IDs of other processes can be stored. A process can communicate with processes whose IDs are stored in its registers and can send them the content of its registers. The state reachability problem asks whether a DRA reaches a configuration where at least one process is in an error state. We first show that this problem is in general undecidable. This result holds even when we restrict the analysis to configurations where the maximal length of the simple paths in their underlying (un)directed communication graphs are bounded by some constant. Then we introduce the model of degenerative DRA which allows non-deterministic reset of the registers. We prove that for every given DRA, its corresponding degenerative one has the same set of reachable states. While the state reachability of a degenerative DRA remains undecidable, we show that the problem becomes decidable with nonprimitive recursive complexity when we restrict the analysis to strongly bounded configurations, i.e. configurations whose underlying undirected graphs have bounded simple paths. Finally, we consider the class of strongly safe DRA, where all the reachable configurations are assumed to be strongly bounded. We show that for strongly safe DRA, the state reachability problem becomes decidable.
Cite as

Parosh Aziz Abdulla, Mohamed Faouzi Atig, Ahmet Kara, and Othmane Rezine. Verification of Dynamic Register Automata. In 34th International Conference on Foundation of Software Technology and Theoretical Computer Science (FSTTCS 2014). Leibniz International Proceedings in Informatics (LIPIcs), Volume 29, pp. 653-665, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)

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@InProceedings{abdulla_et_al:LIPIcs.FSTTCS.2014.653,
  author =	{Abdulla, Parosh Aziz and Atig, Mohamed Faouzi and Kara, Ahmet and Rezine, Othmane},
  title =	{{Verification of  Dynamic Register Automata}},
  booktitle =	{34th International Conference on Foundation of Software Technology and Theoretical Computer Science (FSTTCS 2014)},
  pages =	{653--665},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-77-4},
  ISSN =	{1868-8969},
  year =	{2014},
  volume =	{29},
  editor =	{Raman, Venkatesh and Suresh, S. P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2014.653},
  URN =		{urn:nbn:de:0030-drops-48787},
  doi =		{10.4230/LIPIcs.FSTTCS.2014.653},
  annote =	{Keywords: Verification, Reachability problem, Register automata}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2010.481
Temporal Logics on Words with Multiple Data Values

Authors: Ahmet Kara, Thomas Schwentick, and Thomas Zeume

Published in: LIPIcs, Volume 8, IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2010)

Abstract
The paper proposes and studies temporal logics for attributed words, that is, data words with a (finite) set of (attribute,value)-pairs at each position. It considers a basic logic which is a semantical fragment of the logic $\LTL^\downarrow_1$ of Demri and Lazic with operators for navigation into the future and the past. By reduction to the emptiness problem for data automata it is shown that this basic logic is decidable. Whereas the basic logic only allows navigation to positions where a fixed data value occurs, extensions are studied that also allow navigation to positions with different data values. Besides some undecidable results it is shown that the extension by a certain UNTIL-operator with an inequality target condition remains decidable.
Cite as

Ahmet Kara, Thomas Schwentick, and Thomas Zeume. Temporal Logics on Words with Multiple Data Values. In IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2010). Leibniz International Proceedings in Informatics (LIPIcs), Volume 8, pp. 481-492, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2010)

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@InProceedings{kara_et_al:LIPIcs.FSTTCS.2010.481,
  author =	{Kara, Ahmet and Schwentick, Thomas and Zeume, Thomas},
  title =	{{Temporal Logics on Words with Multiple Data Values}},
  booktitle =	{IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2010)},
  pages =	{481--492},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-23-1},
  ISSN =	{1868-8969},
  year =	{2010},
  volume =	{8},
  editor =	{Lodaya, Kamal and Mahajan, Meena},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2010.481},
  URN =		{urn:nbn:de:0030-drops-28883},
  doi =		{10.4230/LIPIcs.FSTTCS.2010.481},
  annote =	{Keywords: Expressiveness, Decidability, Temporal Logic, Data words}
}
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