boolean () { if (!canResolve()) return true; if (resolve() != null) { return false; } final ContextProvider provider = getElement().getXPathContext(); final NamespaceContext namespaceContext = provider.getNamespaceContext(); assert namespaceContext != null; final String prefix = getCanonicalText(); return !namespaceContext.getKnownPrefixes(provider.getContextElement()).contains(prefix); }