Spanner Evaluation over SLP-Compressed Documents

Schmid, Markus L.; Schweikardt, Nicole

doi:10.1145/3452021.3458325

Cited by 9 publications

(27 citation statements)

References 14 publications

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“…The following ref-words (irst introduced in [48]) are convenient for deining the semantics of xregex (Section 3). They have also been used in [32] and for so-called document spanners in [24,30,31,50,51]. Ref-words will be vital in our deinition of conjunctive xregex (Section 4.1), which are the basis of the class CXRPQ.…”

Section: Ref-wordsmentioning

confidence: 99%

Conjunctive Regular Path Queries with Capture Groups

Schmid

2022

ACM Trans. Database Syst.

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In practice, regular expressions are usually extended by so-called capture groups or capture variables, which allow to capture a subexpression by a variable that can be referenced in the regular expression in order to describe repetitions of subwords. We investigate how this concept could be used for pattern-based graph querying, i. e., we investigate conjunctive regular path queries (CRPQs) that are extended by capture variables. If capture variables are added to CRPQs in a completely unrestricted way, then Boolean evaluation becomes PSPACE-hard in data complexity, even for single-edge graph patterns. On the other hand, if capture variables do not occur under a Kleene star, then the data complexity drops to NL-completeness. Combined complexity is in EXPSPACE, but drops to PSPACE-completeness if the depth (i. e., the nesting depth of capture variables) is bounded, and it drops to NP-completeness if the size of the images of capture variables is bounded by a constant (regardless of the depth or of whether capture variables occur under a Kleene star). In the application of regular expressions as string searching tools, references to capture variables only describe exact repetitions of subwords (i. e., they implement the equality relation on strings). Following recent developments in graph database research, we also study CRPQs with capture variables that describe arbitrary regular relations. We show that if the expressions have depth 0, or if the the size of the images of capture variables is bounded by a constant, then we can allow arbitrary regular relations, while staying in the same complexity bounds. We also investigate the problems of checking whether a given tuple is in the solution set, and computing the whole solution set. On the conceptual side, we add capture variables to CRPQs in such a way that they can be defined in an expression on one arc of the graph pattern, but also referenced in expressions on other arcs. Hence, they add to CRPQs the possibility to define inter-dependencies between different paths, which is a relevant feature of pattern-based graph querying.

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Section: Ref-wordsmentioning

confidence: 99%

Conjunctive Regular Path Queries with Capture Groups

Schmid

2022

ACM Trans. Database Syst.

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“…Their prominence in various areas of computer science is due to the fact that they are mathematically easy, and that they cover many practically applied dictionary-based compression schemes (e. g., run-length encoding and the Lempel-Ziv-family LZ77, LZ78, LZW, etc.). A comprehensive introduction to SLPs is beyond the scope of this overview (we refer to the survey [22] and the papers [21,23,28,29,36,39,41]). In the best case, SLPs can be exponentially smaller than the strings they represent, and since redundancies in texts are likely in practical scenarios, good compressibility is to be expected in most cases.…”

Section: Spanners On Compressed Documentsmentioning

confidence: 99%

“…The papers [39,40] are devoted to the question of how regular document spanners can be evaluated directly over SLP-represented document databases. Let us explain the setting in a bit more detail.…”

Section: Spanners On Compressed Documentsmentioning

confidence: 99%

“…A substantial part of the literature on document spanners has focused on regular spanners. In particular, it has been shown that results of regular spanners can be enumerated with linear preprocessing and constant delay [2,10], the paper [27] is concerned with different semantics of regular spanners and their expressive power, and the articles [39,40] study the evaluation of regular spanners on compressed representations of documents. The paper [32] investigates the evaluation of algebraic expressions over regular spanners.…”

Section: Introductionmentioning

confidence: 99%

“…Section 3 gives an overview of the framework of refl-spanners of [38]. Section 4 focuses on the scenario of [39,40] of spanner evaluation on compressed representations of documents.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Document Spanners - A Brief Overview of Concepts, Results, and Recent Developments

Schmid

Schweikardt

2022

Proceedings of the 41st ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems

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The information extraction framework of document spanners was introduced by Fagin, Kimelfeld, Reiss, and Vansummeren (PODS 2013, J. ACM 2015) as a formalisation of the query language AQL, which is used in IBM's information extraction engine SystemT. Since 2013, this framework has been investigated in depth by the principles of database management community and beyond. The present paper gives a brief overview of concepts, results, and recent developments concerning document spanners. CCS CONCEPTS• Information systems → Information retrieval; • Theory of computation → Database query languages (principles); Data structures and algorithms for data management; Design and analysis of algorithms; Automata extensions; Regular languages.

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The Information Extraction Framework of Document Spanners - A Very Informal Survey

Schmid

2024

Lecture Notes in Computer Science

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Spanner Evaluation over SLP-Compressed Documents

Cited by 9 publications

References 14 publications

Conjunctive Regular Path Queries with Capture Groups

Conjunctive Regular Path Queries with Capture Groups

Document Spanners - A Brief Overview of Concepts, Results, and Recent Developments

The Information Extraction Framework of Document Spanners - A Very Informal Survey

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