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Documents authored by Aamer, Heba

Document
DOI: 10.4230/LIPIcs.ICDT.2025.6
PAC: Computing Join Queries with Semi-Covers

Authors: Heba Aamer and Bas Ketsman

Published in: LIPIcs, Volume 328, 28th International Conference on Database Theory (ICDT 2025)

Abstract
An increased and growing interest in large-scale data processing has triggered a demand for specialized algorithms that thrive in massively parallel shared-nothing systems. To answer the question of how to efficiently compute join queries in this setting, a rich line of research has emerged specifically for the Massively Parallel Communication (MPC) model. In the MPC model, algorithms are executed in rounds, with each round consisting of a synchronized communication phase and a separate local computation phase. The main cost measure is the load of the algorithm, defined as the maximum number of messages received by any server in any round. We study worst-case optimal algorithms for the join query evaluation problem in the constant-round MPC model. In the single-round variant of MPC, the worst-case optimal load for this problem is well understood and algorithms exist that guarantee this load for any join query. In the constant-round variant of MPC, queries can often be computed with a lower load compared to the single-round variant, but the worst-case optimal load is only known for specific classes of join queries, including graph-like and acyclic join queries, and the associated algorithms use very different techniques. In this paper, we propose a new constant-round MPC algorithm for computing join queries. Our algorithm is correct for every join query and its load matches (up to a polylog factor) the worst-case optimal load for at least all join queries that are acyclic or graph-like.
Cite as

Heba Aamer and Bas Ketsman. PAC: Computing Join Queries with Semi-Covers. In 28th International Conference on Database Theory (ICDT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 328, pp. 6:1-6:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{aamer_et_al:LIPIcs.ICDT.2025.6,
  author =	{Aamer, Heba and Ketsman, Bas},
  title =	{{PAC: Computing Join Queries with Semi-Covers}},
  booktitle =	{28th International Conference on Database Theory (ICDT 2025)},
  pages =	{6:1--6:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-364-5},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{328},
  editor =	{Roy, Sudeepa and Kara, Ahmet},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2025.6},
  URN =		{urn:nbn:de:0030-drops-229474},
  doi =		{10.4230/LIPIcs.ICDT.2025.6},
  annote =	{Keywords: Worst-case optimal load, MPC model, join queries}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2021.8
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.
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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
DOI: 10.4230/LIPIcs.ICDT.2020.4
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}
}
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