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- Title
THE COMPLEXITY OF AGGREGATES OVER EXTRACTIONS BY REGULAR EXPRESSIONS.
- Authors
DOLESCHAL, JOHANNES; KIMELFELD, BENNY; MARTENS, WIM
- 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).
- Subjects
RELATION algebras; POLYNOMIAL time algorithms; WRENCHES; COMPUTATIONAL complexity; DATA mining
- Publication
Logical Methods in Computer Science (LMCS), 2023, Vol 19, Issue 3, p1
- ISSN
1860-5974
- Publication type
Article
- DOI
10.46298/LMCS-19(3:12)2023