3 Search Results for "Doleschal, Johannes"

Document
DOI: 10.4230/LIPIcs.ICDT.2021.10
The Complexity of Aggregates over Extractions by Regular Expressions

Authors: Johannes Doleschal, Noa Bratman, Benny Kimelfeld, and Wim Martens

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

Abstract
Regular expressions with capture variables, also known as "regex-formulas", extract relations of spans (intervals identified by their start and end indices) from text. In turn, the class of regular document spanners is the closure of the regex formulas under the Relational Algebra. We investigate the computational complexity of querying text by aggregate functions, such as sum, average, and quantile, on top of regular document spanners. To this end, we formally define aggregate functions over regular document spanners and analyze the computational complexity of exact and approximate computation. More precisely, we show that in a restricted case, all studied aggregate functions can be computed in polynomial time. In general, however, even though exact computation is intractable, some aggregates can still be approximated with fully polynomial-time randomized approximation schemes (FPRAS).
Cite as

Johannes Doleschal, Noa Bratman, Benny Kimelfeld, and Wim Martens. The Complexity of Aggregates over Extractions by Regular Expressions. In 24th International Conference on Database Theory (ICDT 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 186, pp. 10:1-10:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{doleschal_et_al:LIPIcs.ICDT.2021.10,
  author =	{Doleschal, Johannes and Bratman, Noa and Kimelfeld, Benny and Martens, Wim},
  title =	{{The Complexity of Aggregates over Extractions by Regular Expressions}},
  booktitle =	{24th International Conference on Database Theory (ICDT 2021)},
  pages =	{10:1--10:20},
  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-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2021.10},
  URN =		{urn:nbn:de:0030-drops-137181},
  doi =		{10.4230/LIPIcs.ICDT.2021.10},
  annote =	{Keywords: Information extraction, document spanners, regular expressions, aggregation functions}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2020.8
Weight Annotation in Information Extraction

Authors: Johannes Doleschal, Benny Kimelfeld, Wim Martens, and Liat Peterfreund

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

Abstract
The framework of document spanners abstracts the task of information extraction from text as a function that maps every document (a string) into a relation over the document’s spans (intervals identified by their start and end indices). For instance, the regular spanners are the closure under the Relational Algebra (RA) of the regular expressions with capture variables, and the expressive power of the regular spanners is precisely captured by the class of vset-automata - a restricted class of transducers that mark the endpoints of selected spans. In this work, we embark on the investigation of document spanners that can annotate extractions with auxiliary information such as confidence, support, and confidentiality measures. To this end, we adopt the abstraction of provenance semirings by Green et al., where tuples of a relation are annotated with the elements of a commutative semiring, and where the annotation propagates through the (positive) RA operators via the semiring operators. Hence, the proposed spanner extension, referred to as an annotator, maps every string into an annotated relation over the spans. As a specific instantiation, we explore weighted vset-automata that, similarly to weighted automata and transducers, attach semiring elements to transitions. We investigate key aspects of expressiveness, such as the closure under the positive RA, and key aspects of computational complexity, such as the enumeration of annotated answers and their ranked enumeration in the case of numeric semirings. For a number of these problems, fundamental properties of the underlying semiring, such as positivity, are crucial for establishing tractability.
Cite as

Johannes Doleschal, Benny Kimelfeld, Wim Martens, and Liat Peterfreund. Weight Annotation in Information Extraction. In 23rd International Conference on Database Theory (ICDT 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 155, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{doleschal_et_al:LIPIcs.ICDT.2020.8,
  author =	{Doleschal, Johannes and Kimelfeld, Benny and Martens, Wim and Peterfreund, Liat},
  title =	{{Weight Annotation in Information Extraction}},
  booktitle =	{23rd International Conference on Database Theory (ICDT 2020)},
  pages =	{8:1--8:18},
  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-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2020.8},
  URN =		{urn:nbn:de:0030-drops-119325},
  doi =		{10.4230/LIPIcs.ICDT.2020.8},
  annote =	{Keywords: Information extraction, regular document spanners, weighted automata, provenance semirings, K-relations}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2018.14
Satisfiability for SCULPT-Schemas for CSV-Like Data

Authors: Johannes Doleschal, Wim Martens, Frank Neven, and Adam Witkowski

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

Abstract
SCULPT is a simple schema language inspired by the recent working effort towards a recommendation by the World Wide Web Consortium (W3C) for tabular data and metadata on the Web. In its core, a SCULPT schema consists of a set of rules where left-hand sides select sets of regions in the tabular data and the right-hand sides describe the contents of these regions. A document (divided in cells by row- and column-delimiters) then satisfies a schema if it satisfies every rule. In this paper, we study the satisfiability problem for SCULPT schemas. As SCULPT describes grid-like structures, satisfiability obviously becomes undecidable rather quickly even for very restricted schemas. We define a schema language called L-SCULPT (Lego SCULPT) that restricts the walking power of SCULPT by selecting rectangular shaped areas and only considers tables for which selected regions do not intersect. Depending on the axes used by L-SCULPT, we show that satisfiability is PTIME-complete or undecidable. One of the tractable fragments is practically useful as it extends the structural core of the current W3C proposal for schemas over tabular data. We therefore see how the navigational power of the W3C proposal can be extended while still retaining tractable satisfiability tests.
Cite as

Johannes Doleschal, Wim Martens, Frank Neven, and Adam Witkowski. Satisfiability for SCULPT-Schemas for CSV-Like Data. In 21st International Conference on Database Theory (ICDT 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 98, pp. 14:1-14:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{doleschal_et_al:LIPIcs.ICDT.2018.14,
  author =	{Doleschal, Johannes and Martens, Wim and Neven, Frank and Witkowski, Adam},
  title =	{{Satisfiability for SCULPT-Schemas for CSV-Like Data}},
  booktitle =	{21st International Conference on Database Theory (ICDT 2018)},
  pages =	{14:1--14:19},
  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.2018.14},
  URN =		{urn:nbn:de:0030-drops-85969},
  doi =		{10.4230/LIPIcs.ICDT.2018.14},
  annote =	{Keywords: CSV, schema languages, semi-structured data}
}
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