Skyline Operators for Document Spanners

Authors Antoine Amarilli , Benny Kimelfeld , Sébastien Labbé, Stefan Mengel

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Author Details

Antoine Amarilli
  • LTCI, Télécom Paris, Institut Polytechnique de Paris, France
Benny Kimelfeld
  • Technion - Israel Institute of Technology, Haifa, Israel
Sébastien Labbé
  • École normale supérieure, Paris, France
Stefan Mengel
  • Univ. Artois, CNRS, Centre de Recherche en Informatique de Lens (CRIL), France

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Antoine Amarilli, Benny Kimelfeld, Sébastien Labbé, and Stefan Mengel. Skyline Operators for Document Spanners. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 7:1-7:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)


When extracting a relation of spans (intervals) from a text document, a common practice is to filter out tuples of the relation that are deemed dominated by others. The domination rule is defined as a partial order that varies along different systems and tasks. For example, we may state that a tuple is dominated by tuples that extend it by assigning additional attributes, or assigning larger intervals. The result of filtering the relation would then be the skyline according to this partial order. As this filtering may remove most of the extracted tuples, we study whether we can improve the performance of the extraction by compiling the domination rule into the extractor. To this aim, we introduce the skyline operator for declarative information extraction tasks expressed as document spanners. We show that this operator can be expressed via regular operations when the domination partial order can itself be expressed as a regular spanner, which covers several natural domination rules. Yet, we show that the skyline operator incurs a computational cost (under combined complexity). First, there are cases where the operator requires an exponential blowup on the number of states needed to represent the spanner as a sequential variable-set automaton. Second, the evaluation may become computationally hard. Our analysis more precisely identifies classes of domination rules for which the combined complexity is tractable or intractable.

Subject Classification

ACM Subject Classification
  • Information systems → Information extraction
  • Theory of computation → Database query processing and optimization (theory)
  • Information Extraction
  • Document Spanners
  • Query Evaluation


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