@Override
  public boolean isUnresolved() {
    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);
  }
@Override
  public boolean isUnresolved()