33 Search Results for "Schweikardt, Nicole"


Volume

Dagstuhl Follow-Ups, Volume 5

Data Exchange, Integration, and Streams

Editors: Phokion G. Kolaitis, Maurizio Lenzerini, and Nicole Schweikardt

Document
Counting Homomorphisms from Hypergraphs of Bounded Generalised Hypertree Width: A Logical Characterisation

Authors: Benjamin Scheidt and Nicole Schweikardt

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


Abstract
We introduce the 2-sorted counting logic GC^k and its restriction RGC^k that express properties of hypergraphs. These logics have available k variables to address hyperedges, an unbounded number of variables to address vertices of a hypergraph, and atomic formulas E(e,v) to express that a vertex v is contained in a hyperedge e. We show that two hypergraphs H,H' satisfy the same sentences of the logic RGC^k if, and only if, they are homomorphism indistinguishable over the class of hypergraphs of generalised hypertree width at most k. Here, H,H' are called homomorphism indistinguishable over a class 𝒞 if for every hypergraph G ∈ 𝒞 the number of homomorphisms from G to H equals the number of homomorphisms from G to H'. This result can be viewed as a lifting (from graphs to hypergraphs) of a result by Dvořák (2010) stating that any two (undirected, simple, finite) graphs H,H' are indistinguishable by the k+1-variable counting logic C^{k+1} if, and only if, they are homomorphism indistinguishable over the class of graphs of tree-width at most k.

Cite as

Benjamin Scheidt and Nicole Schweikardt. Counting Homomorphisms from Hypergraphs of Bounded Generalised Hypertree Width: A Logical Characterisation. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 79:1-79:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{scheidt_et_al:LIPIcs.MFCS.2023.79,
  author =	{Scheidt, Benjamin and Schweikardt, Nicole},
  title =	{{Counting Homomorphisms from Hypergraphs of Bounded Generalised Hypertree Width: A Logical Characterisation}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{79:1--79:15},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.79},
  URN =		{urn:nbn:de:0030-drops-186131},
  doi =		{10.4230/LIPIcs.MFCS.2023.79},
  annote =	{Keywords: counting logics, guarded logics, homomorphism counting, hypertree decompositions, hypergraphs, incidence graphs, quantum graphs}
}
Document
Constant-Delay Enumeration for SLP-Compressed Documents

Authors: Martín Muñoz and Cristian Riveros

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


Abstract
We study the problem of enumerating results from a query over a compressed document. The model we use for compression are straight-line programs (SLPs), which are defined by a context-free grammar that produces a single string. For our queries we use a model called Annotated Automata, an extension of regular automata that allows annotations on letters. This model extends the notion of Regular Spanners as it allows arbitrarily long outputs. Our main result is an algorithm which evaluates such a query by enumerating all results with output-linear delay after a preprocessing phase which takes linear time on the size of the SLP, and cubic time over the size of the automaton. This is an improvement over Schmid and Schweikardt’s result [Markus L. Schmid and Nicole Schweikardt, 2021], which, with the same preprocessing time, enumerates with a delay which is logarithmic on the size of the uncompressed document. We achieve this through a persistent data structure named Enumerable Compact Sets with Shifts which guarantees output-linear delay under certain restrictions. These results imply constant-delay enumeration algorithms in the context of regular spanners. Further, we use an extension of annotated automata which utilizes succinctly encoded annotations to save an exponential factor from previous results that dealt with constant-delay enumeration over vset automata. Lastly, we extend our results in the same fashion Schmid and Schweikardt did [Markus L. Schmid and Nicole Schweikardt, 2022] to allow complex document editing while maintaining the constant-delay guarantee.

Cite as

Martín Muñoz and Cristian Riveros. Constant-Delay Enumeration for SLP-Compressed Documents. In 26th International Conference on Database Theory (ICDT 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 255, pp. 7:1-7:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{munoz_et_al:LIPIcs.ICDT.2023.7,
  author =	{Mu\~{n}oz, Mart{\'\i}n and Riveros, Cristian},
  title =	{{Constant-Delay Enumeration for SLP-Compressed Documents}},
  booktitle =	{26th International Conference on Database Theory (ICDT 2023)},
  pages =	{7:1--7:17},
  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.2023.7},
  URN =		{urn:nbn:de:0030-drops-177495},
  doi =		{10.4230/LIPIcs.ICDT.2023.7},
  annote =	{Keywords: SLP compression, query evaluation, enumeration algorithms}
}
Document
Discovering Event Queries from Traces: Laying Foundations for Subsequence-Queries with Wildcards and Gap-Size Constraints

Authors: Sarah Kleest-Meißner, Rebecca Sattler, Markus L. Schmid, Nicole Schweikardt, and Matthias Weidlich

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


Abstract
We introduce subsequence-queries with wildcards and gap-size constraints (swg-queries, for short) as a tool for querying event traces. An swg-query q is given by a string s over an alphabet of variables and types, a global window size w, and a tuple c = ((c^-_1, c^+_1), (c^-_2, c^+_2), …, (c^-_{|s|-1}, c^+_{|s|-1})) of local gap-size constraints over ℕ × (ℕ ∪ {∞}). The query q matches in a trace t (i. e., a sequence of types) if the variables can uniformly be substituted by types such that the resulting string occurs in t as a subsequence that spans an area of length at most w, and the i^{th} gap of the subsequence (i. e., the distance between the i^{th} and (i+1)^{th} position of the subsequence) has length at least c^-_i and at most c^+_i. We formalise and investigate the task of discovering an swg-query that describes best the traces from a given sample S of traces, and we present an algorithm solving this task. As a central component, our algorithm repeatedly solves the matching problem (i. e., deciding whether a given query q matches in a given trace t), which is an NP-complete problem (in combined complexity). Hence, the matching problem is of special interest in the context of query discovery, and we therefore subject it to a detailed (parameterised) complexity analysis to identify tractable subclasses, which lead to tractable subclasses of the discovery problem as well. We complement this by a reduction proving that any query discovery algorithm also yields an algorithm for the matching problem. Hence, lower bounds on the complexity of the matching problem directly translate into according lower bounds of the query discovery problem. As a proof of concept, we also implemented a prototype of our algorithm and tested it on real-world data.

Cite as

Sarah Kleest-Meißner, Rebecca Sattler, Markus L. Schmid, Nicole Schweikardt, and Matthias Weidlich. Discovering Event Queries from Traces: Laying Foundations for Subsequence-Queries with Wildcards and Gap-Size Constraints. In 25th International Conference on Database Theory (ICDT 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 220, pp. 18:1-18:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


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@InProceedings{kleestmeiner_et_al:LIPIcs.ICDT.2022.18,
  author =	{Kleest-Mei{\ss}ner, Sarah and Sattler, Rebecca and Schmid, Markus L. and Schweikardt, Nicole and Weidlich, Matthias},
  title =	{{Discovering Event Queries from Traces: Laying Foundations for Subsequence-Queries with Wildcards and Gap-Size Constraints}},
  booktitle =	{25th International Conference on Database Theory (ICDT 2022)},
  pages =	{18:1--18:21},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2022.18},
  URN =		{urn:nbn:de:0030-drops-158922},
  doi =		{10.4230/LIPIcs.ICDT.2022.18},
  annote =	{Keywords: event queries on traces, pattern queries on strings, learning descriptive queries, complexity of query evaluation and query learning}
}
Document
A Purely Regular Approach to Non-Regular Core Spanners

Authors: Markus L. Schmid and Nicole Schweikardt

Published in: LIPIcs, Volume 186, 24th International Conference on Database Theory (ICDT 2021)


Abstract
The regular spanners (characterised by vset-automata) are closed under the algebraic operations of union, join and projection, and have desirable algorithmic properties. The core spanners (introduced by Fagin, Kimelfeld, Reiss, and Vansummeren (PODS 2013, JACM 2015) as a formalisation of the core functionality of the query language AQL used in IBM’s SystemT) additionally need string equality selections and it has been shown by Freydenberger and Holldack (ICDT 2016, Theory of Computing Systems 2018) that this leads to high complexity and even undecidability of the typical problems in static analysis and query evaluation. We propose an alternative approach to core spanners: by incorporating the string-equality selections directly into the regular language that represents the underlying regular spanner (instead of treating it as an algebraic operation on the table extracted by the regular spanner), we obtain a fragment of core spanners that, while having slightly weaker expressive power than the full class of core spanners, arguably still covers the intuitive applications of string equality selections for information extraction and has much better upper complexity bounds of the typical problems in static analysis and query evaluation.

Cite as

Markus L. Schmid and Nicole Schweikardt. A Purely Regular Approach to Non-Regular Core Spanners. In 24th International Conference on Database Theory (ICDT 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 186, pp. 4:1-4:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


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@InProceedings{schmid_et_al:LIPIcs.ICDT.2021.4,
  author =	{Schmid, Markus L. and Schweikardt, Nicole},
  title =	{{A Purely Regular Approach to Non-Regular Core Spanners}},
  booktitle =	{24th International Conference on Database Theory (ICDT 2021)},
  pages =	{4:1--4:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-179-5},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{186},
  editor =	{Yi, Ke and Wei, Zhewei},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2021.4},
  URN =		{urn:nbn:de:0030-drops-137124},
  doi =		{10.4230/LIPIcs.ICDT.2021.4},
  annote =	{Keywords: Document spanners, regular expressions with backreferences}
}
Document
Learning Concepts Described By Weight Aggregation Logic

Authors: Steffen van Bergerem and Nicole Schweikardt

Published in: LIPIcs, Volume 183, 29th EACSL Annual Conference on Computer Science Logic (CSL 2021)


Abstract
We consider weighted structures, which extend ordinary relational structures by assigning weights, i.e. elements from a particular group or ring, to tuples present in the structure. We introduce an extension of first-order logic that allows to aggregate weights of tuples, compare such aggregates, and use them to build more complex formulas. We provide locality properties of fragments of this logic including Feferman-Vaught decompositions and a Gaifman normal form for a fragment called FOW₁, as well as a localisation theorem for a larger fragment called FOWA₁. This fragment can express concepts from various machine learning scenarios. Using the locality properties, we show that concepts definable in FOWA₁ over a weighted background structure of at most polylogarithmic degree are agnostically PAC-learnable in polylogarithmic time after pseudo-linear time preprocessing.

Cite as

Steffen van Bergerem and Nicole Schweikardt. Learning Concepts Described By Weight Aggregation Logic. In 29th EACSL Annual Conference on Computer Science Logic (CSL 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 183, pp. 10:1-10:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


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@InProceedings{vanbergerem_et_al:LIPIcs.CSL.2021.10,
  author =	{van Bergerem, Steffen and Schweikardt, Nicole},
  title =	{{Learning Concepts Described By Weight Aggregation Logic}},
  booktitle =	{29th EACSL Annual Conference on Computer Science Logic (CSL 2021)},
  pages =	{10:1--10:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-175-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{183},
  editor =	{Baier, Christel and Goubault-Larrecq, Jean},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2021.10},
  URN =		{urn:nbn:de:0030-drops-134447},
  doi =		{10.4230/LIPIcs.CSL.2021.10},
  annote =	{Keywords: first-order definable concept learning, agnostic probably approximately correct learning, classification problems, locality, Feferman-Vaught decomposition, Gaifman normal form, first-order logic with counting, weight aggregation logic}
}
Document
Enumeration in Data Management (Dagstuhl Seminar 19211)

Authors: Endre Boros, Benny Kimelfeld, Reinhard Pichler, and Nicole Schweikardt

Published in: Dagstuhl Reports, Volume 9, Issue 5 (2019)


Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 19211 "Enumeration in Data Management". The goal of the seminar was to bring together researchers from various fields of computer science, including the Databases, Computational Logic, and Algorithms communities, and establish the means of collaboration towards considerable progress on the topic. Specifically, we aimed at understanding the recent developments, identifying the important open problems, and initiating collaborative efforts towards solutions thereof. In addition, we aimed to build and disseminate a toolkit for data-centric enumeration problems, including algorithmic techniques, proof techniques, and important indicator problems. Towards the objectives, the seminar included tutorials on the topic, invited talks, presentations of open problems, working groups on the open problems, discussions on platforms to compile the community knowledge, and the construction of various skeletons of such compilations.

Cite as

Endre Boros, Benny Kimelfeld, Reinhard Pichler, and Nicole Schweikardt. Enumeration in Data Management (Dagstuhl Seminar 19211). In Dagstuhl Reports, Volume 9, Issue 5, pp. 89-109, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@Article{boros_et_al:DagRep.9.5.89,
  author =	{Boros, Endre and Kimelfeld, Benny and Pichler, Reinhard and Schweikardt, Nicole},
  title =	{{Enumeration in Data Management (Dagstuhl Seminar 19211)}},
  pages =	{89--109},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2019},
  volume =	{9},
  number =	{5},
  editor =	{Boros, Endre and Kimelfeld, Benny and Pichler, Reinhard and Schweikardt, Nicole},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.9.5.89},
  URN =		{urn:nbn:de:0030-drops-113822},
  doi =		{10.4230/DagRep.9.5.89},
  annote =	{Keywords: constant delay, databases, dynamic complexity, enumeration, polynomial delay, query evaluation}
}
Document
Constant Delay Enumeration with FPT-Preprocessing for Conjunctive Queries of Bounded Submodular Width

Authors: Christoph Berkholz and Nicole Schweikardt

Published in: LIPIcs, Volume 138, 44th International Symposium on Mathematical Foundations of Computer Science (MFCS 2019)


Abstract
Marx (STOC 2010, J. ACM 2013) introduced the notion of submodular width of a conjunctive query (CQ) and showed that for any class Phi of Boolean CQs of bounded submodular width, the model-checking problem for Phi on the class of all finite structures is fixed-parameter tractable (FPT). Note that for non-Boolean queries, the size of the query result may be far too large to be computed entirely within FPT time. We investigate the free-connex variant of submodular width and generalise Marx’s result to non-Boolean queries as follows: For every class Phi of CQs of bounded free-connex submodular width, within FPT-preprocessing time we can build a data structure that allows to enumerate, without repetition and with constant delay, all tuples of the query result. Our proof builds upon Marx’s splitting routine to decompose the query result into a union of results; but we have to tackle the additional technical difficulty to ensure that these can be enumerated efficiently.

Cite as

Christoph Berkholz and Nicole Schweikardt. Constant Delay Enumeration with FPT-Preprocessing for Conjunctive Queries of Bounded Submodular Width. In 44th International Symposium on Mathematical Foundations of Computer Science (MFCS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 138, pp. 58:1-58:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{berkholz_et_al:LIPIcs.MFCS.2019.58,
  author =	{Berkholz, Christoph and Schweikardt, Nicole},
  title =	{{Constant Delay Enumeration with FPT-Preprocessing for Conjunctive Queries of Bounded Submodular Width}},
  booktitle =	{44th International Symposium on Mathematical Foundations of Computer Science (MFCS 2019)},
  pages =	{58:1--58:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-117-7},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{138},
  editor =	{Rossmanith, Peter and Heggernes, Pinar and Katoen, Joost-Pieter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2019.58},
  URN =		{urn:nbn:de:0030-drops-110021},
  doi =		{10.4230/LIPIcs.MFCS.2019.58},
  annote =	{Keywords: conjunctive queries, constant delay enumeration, hypertree decompositions, submodular width, fixed-parameter tractability}
}
Document
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
Gaifman Normal Forms for Counting Extensions of First-Order Logic

Authors: Dietrich Kuske and Nicole Schweikardt

Published in: LIPIcs, Volume 107, 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)


Abstract
We consider the extension of first-order logic FO by unary counting quantifiers and generalise the notion of Gaifman normal form from FO to this setting. For formulas that use only ultimately periodic counting quantifiers, we provide an algorithm that computes equivalent formulas in Gaifman normal form. We also show that this is not possible for formulas using at least one quantifier that is not ultimately periodic. Now let d be a degree bound. We show that for any formula phi with arbitrary counting quantifiers, there is a formula gamma in Gaifman normal form that is equivalent to phi on all finite structures of degree <= d. If the quantifiers of phi are decidable (decidable in elementary time, ultimately periodic), gamma can be constructed effectively (in elementary time, in worst-case optimal 3-fold exponential time). For the setting with unrestricted degree we show that by using our Gaifman normal form for formulas with only ultimately periodic counting quantifiers, a known fixed-parameter tractability result for FO on classes of structures of bounded local tree-width can be lifted to the extension of FO with ultimately periodic counting quantifiers (a logic equally expressive as FO+MOD, i.e., first-oder logic with modulo-counting quantifiers).

Cite as

Dietrich Kuske and Nicole Schweikardt. Gaifman Normal Forms for Counting Extensions of First-Order Logic. In 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 107, pp. 133:1-133:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)


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@InProceedings{kuske_et_al:LIPIcs.ICALP.2018.133,
  author =	{Kuske, Dietrich and Schweikardt, Nicole},
  title =	{{Gaifman Normal Forms for Counting Extensions of First-Order Logic}},
  booktitle =	{45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)},
  pages =	{133:1--133:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-076-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{107},
  editor =	{Chatzigiannakis, Ioannis and Kaklamanis, Christos and Marx, D\'{a}niel and Sannella, Donald},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2018.133},
  URN =		{urn:nbn:de:0030-drops-91375},
  doi =		{10.4230/LIPIcs.ICALP.2018.133},
  annote =	{Keywords: Finite model theory, Gaifman locality, modulo-counting quantifiers, fixed parameter tractable model-checking}
}
Document
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)


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@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.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
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)


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@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.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}
}
Document
Invited Talk
Using Locality for Efficient Query Evaluation in Various Computation Models (Invited Talk)

Authors: Nicole Schweikardt

Published in: LIPIcs, Volume 31, 18th International Conference on Database Theory (ICDT 2015)


Abstract
In the database theory and logic literature, different notions of locality of queries have been studied, the most prominent being Hanf locality and Gaifman locality. These notions are designed so that, in order to evaluate a local query in a given database, it suffices to look only at small neighbourhoods around tuples of elements that belong to the database. In this talk I want to give a survey of how to use locality for efficient query evaluation in various computation models. In particular, we will take a closer look at how to enumerate query results with constant delay, and at how to evaluate queries in a map-reduce like setting [Neven et al., ICDT 2015] or in Pregel [Malewicz et al., SIGMOD 2010]. Also, we will have a closer look at how to transform a given local query into a form suitable for exploiting its locality.

Cite as

Nicole Schweikardt. Using Locality for Efficient Query Evaluation in Various Computation Models (Invited Talk). In 18th International Conference on Database Theory (ICDT 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 31, pp. 13-14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)


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@InProceedings{schweikardt:LIPIcs.ICDT.2015.13,
  author =	{Schweikardt, Nicole},
  title =	{{Using Locality for Efficient Query Evaluation in Various Computation Models}},
  booktitle =	{18th International Conference on Database Theory (ICDT 2015)},
  pages =	{13--14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-79-8},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{31},
  editor =	{Arenas, Marcelo and Ugarte, Mart{\'\i}n},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2015.13},
  URN =		{urn:nbn:de:0030-drops-49987},
  doi =		{10.4230/LIPIcs.ICDT.2015.13},
  annote =	{Keywords: query evaluation, locality}
}
Document
Distributed Streaming with Finite Memory

Authors: Frank Neven, Nicole Schweikardt, Frédéric Servais, and Tony Tan

Published in: LIPIcs, Volume 31, 18th International Conference on Database Theory (ICDT 2015)


Abstract
We introduce three formal models of distributed systems for query evaluation on massive databases: Distributed Streaming with Register Automata (DSAs), Distributed Streaming with Register Transducers (DSTs), and Distributed Streaming with Register Transducers and Joins (DSTJs). These models are based on the key-value paradigm where the input is transformed into a dataset of key-value pairs, and on each key a local computation is performed on the values associated with that key resulting in another set of key-value pairs. Computation proceeds in a constant number of rounds, where the result of the last round is the input to the next round, and transformation to key-value pairs is required to be generic. The difference between the three models is in the local computation part. In DSAs it is limited to making one pass over its input using a register automaton, while in DSTs it can make two passes: in the first pass it uses a finite-state automaton and in the second it uses a register transducer. The third model DSTJs is an extension of DSTs, where local computations are capable of constructing the Cartesian product of two sets. We obtain the following results: (1) DSAs can evaluate first-order queries over bounded degree databases; (2) DSTs can evaluate semijoin algebra queries over arbitrary databases; (3) DSTJs can evaluate the whole relational algebra over arbitrary databases; (4) DSTJs are strictly stronger than DSTs, which in turn, are strictly stronger than DSAs; (5) within DSAs, DSTs and DSTJs there is a strict hierarchy w.r.t. the number of rounds.

Cite as

Frank Neven, Nicole Schweikardt, Frédéric Servais, and Tony Tan. Distributed Streaming with Finite Memory. In 18th International Conference on Database Theory (ICDT 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 31, pp. 324-341, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)


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@InProceedings{neven_et_al:LIPIcs.ICDT.2015.324,
  author =	{Neven, Frank and Schweikardt, Nicole and Servais, Fr\'{e}d\'{e}ric and Tan, Tony},
  title =	{{Distributed Streaming with Finite Memory}},
  booktitle =	{18th International Conference on Database Theory (ICDT 2015)},
  pages =	{324--341},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-79-8},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{31},
  editor =	{Arenas, Marcelo and Ugarte, Mart{\'\i}n},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2015.324},
  URN =		{urn:nbn:de:0030-drops-49939},
  doi =		{10.4230/LIPIcs.ICDT.2015.324},
  annote =	{Keywords: distributed systems, relational algebra, semijoin algebra, register automata, register transducers.}
}
Document
Complete Volume
DFU, Volume 5, Data Exchange, Integration, and Streams, Complete Volume

Authors: Phokion G. Kolaitis, Maurizio Lenzerini, and Nicole Schweikardt

Published in: Dagstuhl Follow-Ups, Volume 5, Data Exchange, Integration, and Streams (2013)


Abstract
DFU, Volume 5, Data Exchange, Information, and Streams, Complete Volume

Cite as

Data Exchange, Integration, and Streams. Dagstuhl Follow-Ups, Volume 5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2013)


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@Collection{DFU.Vol5.10452,
  title =	{{DFU, Volume 5, Data Exchange, Integration, and Streams, Complete Volume}},
  booktitle =	{Data Exchange, Integration, and Streams},
  series =	{Dagstuhl Follow-Ups},
  ISBN =	{978-3-939897-61-3},
  ISSN =	{1868-8977},
  year =	{2013},
  volume =	{5},
  editor =	{Kolaitis, Phokion G. and Lenzerini, Maurizio and Schweikardt, Nicole},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DFU.Vol5.10452},
  URN =		{urn:nbn:de:0030-drops-43032},
  doi =		{10.4230/DFU.Vol5.10452},
  annote =	{Keywords: Heterogeneous Databases, Systems, Database Applications, Nonnumerical Algorithms and Problems}
}
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