SHACL is the default RDF validator, and it is open-world: it validates the terms a shape targets and stays silent about everything else. So when a model emits a plausible-but-nonexistent ontology term, SHACL reports conforms=true and the fabricated data flows on. A closed-world vocabulary gate catches it. Pick a vocabulary, keep the preloaded example or paste your own RDF, and press Run. Real pyshacl runs in your browser via Pyodide.