SHACL (Shapes Constraint Language)

The Shapes Constraint Language (SHACL) is a widely-supported W3C standard that lets us describe conditions that a dataset must meet. As with RDFS schemas and OWL ontologies, SHACL contains metadata about datasets, but this metadata serves a different purpose: to help validate the data instead of enabling inferencing.

Because RDFS schemas and OWL ontologies describe a dataset’s structure by listing classes, properties, and their relationships, many people have thought that these were describing a schema the same way the schema of a relational database or an object-oriented system does — by describing constraints that data must conform to if it will be used in that dataset.

But, they do not. RDFS schemas and OWL ontologies describe these structures to enable inferencing. For example, if an RDFS schema says that the familyName property has a domain of Person, then we can infer that any resource with a familyName property is an instance of the class Person. Neither RDFS nor OWL give you a way to say that familyName is a required property of Person, so that if an instance of Person lacks a familyName value then it is an invalid instance.

This is where SHACL comes in. If you want to say that familyName is a required property for the Person class, or that a Review class’s rating value must be an integer value between 1 and 5, then SHACL lets you do this. This makes SHACL invaluable for ensuring data quality when you manage your RDF knowledge graph using a tool that supports SHACL such as GraphDB.

[from:https://www.ontotext.com/knowledgehub/fundamentals/what-is-shacl/]