Expressiveness of SHACL Features and Extensions for Full Equality and Disjointness Tests

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Main Authors: Bogaerts, Bart, Jakubowski, Maxime, Bussche, Jan Van den
Format: Preprint
Published: 2022
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author Bogaerts, Bart
Jakubowski, Maxime
Bussche, Jan Van den
author_facet Bogaerts, Bart
Jakubowski, Maxime
Bussche, Jan Van den
contents SHACL is a W3C-proposed schema language for expressing structural constraints on RDF graphs. Recent work on formalizing this language has revealed a striking relationship to description logics. SHACL expressions can use three fundamental features that are not so common in description logics. These features are equality tests; disjointness tests; and closure constraints. Moreover, SHACL is peculiar in allowing only a restricted form of expressions (so-called targets) on the left-hand side of inclusion constraints. The goal of this paper is to obtain a clear picture of the impact and expressiveness of these features and restrictions. We show that each of the four features is primitive: using the feature, one can express boolean queries that are not expressible without using the feature. We also show that the restriction that SHACL imposes on allowed targets is inessential, as long as closure constraints are not used. In addition, we show that enriching SHACL with "full" versions of equality tests, or disjointness tests, results in a strictly more powerful language.
format Preprint
id arxiv_https___arxiv_org_abs_2212_03553
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Expressiveness of SHACL Features and Extensions for Full Equality and Disjointness Tests
Bogaerts, Bart
Jakubowski, Maxime
Bussche, Jan Van den
Logic in Computer Science
SHACL is a W3C-proposed schema language for expressing structural constraints on RDF graphs. Recent work on formalizing this language has revealed a striking relationship to description logics. SHACL expressions can use three fundamental features that are not so common in description logics. These features are equality tests; disjointness tests; and closure constraints. Moreover, SHACL is peculiar in allowing only a restricted form of expressions (so-called targets) on the left-hand side of inclusion constraints. The goal of this paper is to obtain a clear picture of the impact and expressiveness of these features and restrictions. We show that each of the four features is primitive: using the feature, one can express boolean queries that are not expressible without using the feature. We also show that the restriction that SHACL imposes on allowed targets is inessential, as long as closure constraints are not used. In addition, we show that enriching SHACL with "full" versions of equality tests, or disjointness tests, results in a strictly more powerful language.
title Expressiveness of SHACL Features and Extensions for Full Equality and Disjointness Tests
topic Logic in Computer Science
url https://arxiv.org/abs/2212.03553