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Documents authored by Van den Bussche, Jan


Document
Expressiveness of SHACL Features

Authors: Bart Bogaerts, Maxime Jakubowski, and Jan Van den Bussche

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


Abstract
SHACL is a W3C-proposed schema language for expressing structural constraints on RDF graphs. Recent work on formalizing this language has revealed a striking relationship to description logics. SHACL expressions can use four fundamental features that are not so common in description logics. These features are zero-or-one path expressions; equality tests; disjointness tests; and closure constraints. Moreover, SHACL is peculiar in allowing only a restricted form of expressions (so-called targets) on the left-hand side of inclusion constraints. The goal of this paper is to obtain a clear picture of the impact and expressiveness of these features and restrictions. We show that each of the four features is primitive: using the feature, one can express boolean queries that are not expressible without using the feature. We also show that the restriction that SHACL imposes on allowed targets is inessential, as long as closure constraints are not used.

Cite as

Bart Bogaerts, Maxime Jakubowski, and Jan Van den Bussche. Expressiveness of SHACL Features. In 25th International Conference on Database Theory (ICDT 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 220, pp. 15:1-15:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)


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@InProceedings{bogaerts_et_al:LIPIcs.ICDT.2022.15,
  author =	{Bogaerts, Bart and Jakubowski, Maxime and Van den Bussche, Jan},
  title =	{{Expressiveness of SHACL Features}},
  booktitle =	{25th International Conference on Database Theory (ICDT 2022)},
  pages =	{15:1--15:16},
  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.2022.15},
  URN =		{urn:nbn:de:0030-drops-158890},
  doi =		{10.4230/LIPIcs.ICDT.2022.15},
  annote =	{Keywords: Expressive power, schema languages}
}
Document
Input-Output Disjointness for Forward Expressions in the Logic of Information Flows

Authors: Heba Aamer and Jan Van den Bussche

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


Abstract
Last year we introduced the logic FLIF (forward logic of information flows) as a declarative language for specifying complex compositions of information sources with limited access patterns. The key insight of this approach is to view a system of information sources as a graph, where the nodes are valuations of variables, so that accesses to information sources can be modeled as edges in the graph. This allows the use of XPath-like navigational graph query languages. Indeed, a well-behaved fragment of FLIF, called io-disjoint FLIF, was shown to be equivalent to the executable fragment of first-order logic. It remained open, however, how io-disjoint FLIF compares to general FLIF . In this paper we close this gap by showing that general FLIF expressions can always be put into io-disjoint form.

Cite as

Heba Aamer and Jan Van den Bussche. Input-Output Disjointness for Forward Expressions in the Logic of Information Flows. In 24th International Conference on Database Theory (ICDT 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 186, pp. 8:1-8:18, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2021)


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@InProceedings{aamer_et_al:LIPIcs.ICDT.2021.8,
  author =	{Aamer, Heba and Van den Bussche, Jan},
  title =	{{Input-Output Disjointness for Forward Expressions in the Logic of Information Flows}},
  booktitle =	{24th International Conference on Database Theory (ICDT 2021)},
  pages =	{8:1--8:18},
  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.2021.8},
  URN =		{urn:nbn:de:0030-drops-137167},
  doi =		{10.4230/LIPIcs.ICDT.2021.8},
  annote =	{Keywords: Composition, expressive power, variable substitution}
}
Document
Executable First-Order Queries in the Logic of Information Flows

Authors: Heba Aamer, Bart Bogaerts, Dimitri Surinx, Eugenia Ternovska, and Jan Van den Bussche

Published in: LIPIcs, Volume 155, 23rd International Conference on Database Theory (ICDT 2020)


Abstract
The logic of information flows (LIF) has recently been proposed as a general framework in the field of knowledge representation. In this framework, tasks of a procedural nature can still be modeled in a declarative, logic-based fashion. In this paper, we focus on the task of query processing under limited access patterns, a well-studied problem in the database literature. We show that LIF is well-suited for modeling this task. Toward this goal, we introduce a variant of LIF called "forward" LIF, in a first-order setting. We define FLIF^io, a syntactical fragment of forward LIF, and show that it corresponds exactly to the "executable" fragment of first-order logic defined by Nash and Ludäscher. The definition of FLIF^io involves a classification of the free variables of an expression into "input" and "output" variables. Our result hinges on inertia and determinacy laws for forward LIF expressions, which are interesting in their own right. These laws are formulated in terms of the input and output variables.

Cite as

Heba Aamer, Bart Bogaerts, Dimitri Surinx, Eugenia Ternovska, and Jan Van den Bussche. Executable First-Order Queries in the Logic of Information Flows. In 23rd International Conference on Database Theory (ICDT 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 155, pp. 4:1-4:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2020)


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@InProceedings{aamer_et_al:LIPIcs.ICDT.2020.4,
  author =	{Aamer, Heba and Bogaerts, Bart and Surinx, Dimitri and Ternovska, Eugenia and Van den Bussche, Jan},
  title =	{{Executable First-Order Queries in the Logic of Information Flows}},
  booktitle =	{23rd International Conference on Database Theory (ICDT 2020)},
  pages =	{4:1--4:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-139-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{155},
  editor =	{Lutz, Carsten and Jung, Jean Christoph},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2020.4},
  URN =		{urn:nbn:de:0030-drops-119284},
  doi =		{10.4230/LIPIcs.ICDT.2020.4},
  annote =	{Keywords: Logic of Information Flows, Limited access pattern, Executable first-order logic}
}
Document
Additive First-Order Queries

Authors: Gerald Berger, Martin Otto, Andreas Pieris, Dimitri Surinx, and Jan Van den Bussche

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


Abstract
A database query q is called additive if q(A U B) = q(A) U q(B) for domain-disjoint input databases A and B. Additivity allows the computation of the query result to be parallelised over the connected components of the input database. We define the "connected formulas" as a syntactic fragment of first-order logic, and show that a first-order query is additive if and only if it expressible by a connected formula. This characterisation specializes to the guarded fragment of first-order logic. We also show that additivity is decidable for formulas of the guarded fragment, establish the computational complexity, and do the same for positive-existential formulas. Our results hold when restricting attention to finite structures, as is common in database theory, but also hold in the unrestricted setting.

Cite as

Gerald Berger, Martin Otto, Andreas Pieris, Dimitri Surinx, and Jan Van den Bussche. Additive First-Order Queries. In 22nd International Conference on Database Theory (ICDT 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 127, pp. 19:1-19:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)


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@InProceedings{berger_et_al:LIPIcs.ICDT.2019.19,
  author =	{Berger, Gerald and Otto, Martin and Pieris, Andreas and Surinx, Dimitri and Van den Bussche, Jan},
  title =	{{Additive First-Order Queries}},
  booktitle =	{22nd International Conference on Database Theory (ICDT 2019)},
  pages =	{19:1--19:14},
  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.2019.19},
  URN =		{urn:nbn:de:0030-drops-103217},
  doi =		{10.4230/LIPIcs.ICDT.2019.19},
  annote =	{Keywords: Expressive power}
}
Document
Expressivity Within Second-Order Transitive-Closure Logic

Authors: Flavio Ferrarotti, Jan Van den Bussche, and Jonni Virtema

Published in: LIPIcs, Volume 119, 27th EACSL Annual Conference on Computer Science Logic (CSL 2018)


Abstract
Second-order transitive-closure logic, SO(TC), is an expressive declarative language that captures the complexity class PSPACE. Already its monadic fragment, MSO(TC), allows the expression of various NP-hard and even PSPACE-hard problems in a natural and elegant manner. As SO(TC) offers an attractive framework for expressing properties in terms of declaratively specified computations, it is interesting to understand the expressivity of different features of the language. This paper focuses on the fragment MSO(TC), as well on the purely existential fragment SO(2TC)(exists); in 2TC, the TC operator binds only tuples of relation variables. We establish that, with respect to expressive power, SO(2TC)(exists) collapses to existential first-order logic. In addition we study the relationship of MSO(TC) to an extension of MSO(TC) with counting features (CMSO(TC)) as well as to order-invariant MSO. We show that the expressive powers of CMSO(TC) and MSO(TC) coincide. Moreover we establish that, over unary vocabularies, MSO(TC) strictly subsumes order-invariant MSO.

Cite as

Flavio Ferrarotti, Jan Van den Bussche, and Jonni Virtema. Expressivity Within Second-Order Transitive-Closure Logic. In 27th EACSL Annual Conference on Computer Science Logic (CSL 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 119, pp. 22:1-22:18, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)


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@InProceedings{ferrarotti_et_al:LIPIcs.CSL.2018.22,
  author =	{Ferrarotti, Flavio and Van den Bussche, Jan and Virtema, Jonni},
  title =	{{Expressivity Within Second-Order Transitive-Closure Logic}},
  booktitle =	{27th EACSL Annual Conference on Computer Science Logic (CSL 2018)},
  pages =	{22:1--22:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-088-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{119},
  editor =	{Ghica, Dan R. and Jung, Achim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2018.22},
  URN =		{urn:nbn:de:0030-drops-96896},
  doi =		{10.4230/LIPIcs.CSL.2018.22},
  annote =	{Keywords: Expressive power, Higher order logics, Descriptive complexity}
}
Document
On the Expressive Power of Query Languages for Matrices

Authors: Robert Brijder, Floris Geerts, Jan Van den Bussche, and Timmy Weerwag

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


Abstract
We investigate the expressive power of MATLANG, a formal language for matrix manipulation based on common matrix operations and linear algebra. The language can be extended with the operation inv of inverting a matrix. In MATLANG + inv we can compute the transitive closure of directed graphs, whereas we show that this is not possible without inversion. Indeed we show that the basic language can be simulated in the relational algebra with arithmetic operations, grouping, and summation. We also consider an operation eigen for diagonalizing a matrix, which is defined so that different eigenvectors returned for a same eigenvalue are orthogonal. We show that inv can be expressed in MATLANG + eigen. We put forward the open question whether there are boolean queries about matrices, or generic queries about graphs, expressible in MATLANG + eigen but not in MATLANG + inv. The evaluation problem for MATLANG + eigen is shown to be complete for the complexity class Exists R.

Cite as

Robert Brijder, Floris Geerts, Jan Van den Bussche, and Timmy Weerwag. On the Expressive Power of Query Languages for Matrices. In 21st International Conference on Database Theory (ICDT 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 98, pp. 10:1-10:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)


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@InProceedings{brijder_et_al:LIPIcs.ICDT.2018.10,
  author =	{Brijder, Robert and Geerts, Floris and Van den Bussche, Jan and Weerwag, Timmy},
  title =	{{On the Expressive Power of Query Languages for Matrices}},
  booktitle =	{21st International Conference on Database Theory (ICDT 2018)},
  pages =	{10:1--10:17},
  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.2018.10},
  URN =		{urn:nbn:de:0030-drops-86007},
  doi =		{10.4230/LIPIcs.ICDT.2018.10},
  annote =	{Keywords: matrix query languages, relational algebra with aggregates, query evaluation problem, graph queries}
}
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