On the Interplay Between Validation and Inference in Shapes Constraint Language – An Investigation on the Time Ontology

This paper presents a Shapes Constraint Language (SHACL)-based framework for validating the Time Ontology ( https://www.w3.org/TR/owl-time ). The Time Ontology, currently a W3C Candidate Recommendation, is widely recognized as the ‘de facto’ standard for representing temporal data in the Semantic Web. However, its current OWL axiomatization cannot enforce several validation constraints on temporal knowledge that can be expressed using the Time Ontology vocabulary. These constraints are instead captured by the SHACL formalization proposed in this paper. Nevertheless, we show that SHACL shapes are insufficient to validate even simple knowledge graphs that can be encoded using this vocabulary. This limitation arises because validation must be performed on the inferred knowledge graph, which SHACL shapes alone cannot derive internally. To address this, our framework first computes the inferred knowledge graph using SHACL-SPARQL rules and then validates it through SHACL shapes. We argue that our findings extend beyond the Time Ontology and have broader implications for SHACL and knowledge graph reasoning. We therefore view our work as a call to action for the Semantic Web community to systematically investigate the interplay between validation and inference. Specifically, there is a need to study the representational requirements of different use cases to identify the minimal set of SHACL shapes and inference rules for data validation in each context. These efforts could ultimately lead to the definition of distinct SHACL dialects, analogous to how OWL Lite, OWL DL, and other profiles were defined for OWL. The shapes and rules that define the proposed framework are available at https://github.com/liviorobaldo/TimeOntologyInSHACL .