SHACL Validation in the Presence of Ontologies: Semantics and Rewriting Techniques

TL;DR

This paper proposes a semantics and rewriting techniques for SHACL validation when combined with OWL ontologies, addressing semantic and computational challenges, and analyzes the complexity of such validation tasks.

Contribution

It introduces a semantics based on core universal models and a rewriting method to reduce SHACL validation with ontologies to standard validation, along with complexity analysis.

Findings

Validation is EXPTIME-complete with simple ontologies.

Validation is PTIME-complete in data complexity.

Finite models enable rewriting techniques for validation.

Abstract

SHACL and OWL are two prominent W3C standards for managing RDF data. These languages share many features, but they have one fundamental difference: OWL, designed for inferring facts from incomplete data, makes the open-world assumption, whereas SHACL is a constraint language that treats the data as complete and must be validated under the closed-world assumption. The combination of both formalisms is very appealing and has been called for, but their semantic gap is a major challenge, semantically and computationally. In this paper, we advocate a semantics for SHACL validation in the presence of ontologies based on core universal models. We provide a technique for constructing these models for ontologies in the rich data-tractable description logic Horn-ALCHIQ. Furthermore, we use a finite representation of this model to develop a rewriting technique that reduces SHACL validation in the presence of ontologies to standard validation. Finally, we study the complexity of SHACL validation in the presence of ontologies, and show that even very simple ontologies make the problem EXPTIME-complete, and PTIME-complete in data complexity.