一句话：证明 SHACL 的相等测试、不相交测试、闭包约束与目标限制各自本原，且完全相等/不相交扩展严格增强表达力。
本文研究 W3C 提出的 RDF 图结构约束模式语言 SHACL 的表达力。近期工作将 SHACL 形式化，并揭示其与描述逻辑的密切联系。SHACL 表达式支持相等测试、不相交测试和闭包约束，且只允许受限形式的目标出现在包含约束左侧。为厘清这些特性与限制的影响，作者从表达力角度进行分析，证明这四个特性都是本原的：使用任一特性都能表达不使用时无法表达的布尔查询。论文还证明，只要不使用闭包约束，SHACL 对目标侧的限制实际上是不必要的。此外，将相等测试或不相交测试扩展为完全版本，会使语言表达力严格增强。
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.
@article{paperbot2775,
title = {Expressiveness of SHACL Features and Extensions for Full Equality and Disjointness Tests},
author = {Bart Bogaerts and Maxime Jakubowski and Jan Van den Bussche},
journal = {Logical Methods in Computer Science},
volume = {Volume 20, Issue 1},
year = {2024},
doi = {10.46298/lmcs-20(1:16)2024}
}