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Expressiveness of SHACL Features Bogaerts, Bart Jakubowski, Maxime Van den Bussche, Jan Expressive power schema languages 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 four fundamental features that are not so common in description logics. These features are zero-or-one path expressions; 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. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Bart Bogaerts and Maxime Jakubowski and Jan Van den Bussche 2022 Is Part Of LIPIcs, Volume 220, 25th International Conference on Database Theory (ICDT 2022) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.ICDT.2022.15 urn:nbn:de:0030-drops-158890 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2022.15 eng https://creativecommons.org/licenses/by/4.0/legalcode