public static string GetOwlVersionInfo(this OntologyResource resource) { if (!resource.HasOwlVersionInfo()) { throw new RdfException($"Resource {resource} does not have an owl:versionInfo annotation"); } INode owlVersionInfo = resource.Graph.CreateUriNode(VocabularyHelper.OWL.versionInfo); return(resource.GetNodesViaPredicate(owlVersionInfo).LiteralNodes().First().Value); }