public static bool IsBuiltIn(this OntologyResource ontologyResource) { if (!ontologyResource.IsNamed()) { return(false); } HashSet <string> builtIns = new HashSet <string>() { "http://www.w3.org/1999/02/22-rdf-syntax-ns#", "http://www.w3.org/2000/01/rdf-schema#", "http://www.w3.org/2002/07/owl#", "http://www.w3.org/2001/XMLSchema#" }; return(builtIns.Any(builtin => ontologyResource.GetUri().AbsoluteUri.Contains(builtin))); }