Johannes Doleschal ; Benny Kimelfeld ; Wim Martens - The Complexity of Aggregates over Extractions by Regular Expressions

lmcs:8623 - Logical Methods in Computer Science, August 9, 2023, Volume 19, Issue 3 - https://doi.org/10.46298/lmcs-19(3:12)2023
The Complexity of Aggregates over Extractions by Regular ExpressionsArticle

Authors: Johannes Doleschal ; Benny Kimelfeld ; Wim Martens

    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).


    Volume: Volume 19, Issue 3
    Published on: August 9, 2023
    Accepted on: June 30, 2023
    Submitted on: October 29, 2021
    Keywords: Computer Science - Databases,Computer Science - Formal Languages and Automata Theory

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