Holger K.

If a commercial enterprise product is an option, there is TopBraid EDG https://www.topquadrant.com

My employer, TopQuadrant offers TopBraid EDG with a number of features related to knowledge graphs, enterprise data management, ontology design, taxonomy editing etc. https://www.topquadrant.com

What we do in our product is that we include a dedicated “systems” graph that is always there and which defines, for example, that xsd:string is an rdfs:Datatype. This means we are decoupled from external graphs for things that are essential for the functioning of our product. Sure, for example, our user interface forms are completely model-driven and have very little hard-coded, except how to look up property definitions and datatypes.

In the case of SHACL, the vocabulary is machine readable on the web and most features attempt to describe themselves there.

I cannot comment on whether the RDF vocabulary itself is dereferencable, if that’s what you mean. But most tools that I know about have some built-in knowledge about how the core of RDF (and related languages) work. For example, the use of rdf:type and rdfs:subClassOf is typically hard-coded into some algorithms.

That's also because many if not most use cases of RDF are in closed (enterprise) applications, where exposing data to the outside is not even desirable. The Semantic Web vision was just one possible use case of RDF, which is a general graph data model.

Wikidata SPARQL endpoint?