@Override
 protected void setNamespaceInternal(String prefix, String name) throws SailException {
   namespaces.setPrefix(prefix, name);
 }
 @Override
 protected void removeNamespaceInternal(String prefix) throws SailException {
   namespaces.removePrefix(prefix);
 }
 @Override
 protected String getNamespaceInternal(String prefix) throws SailException {
   Namespace ns = namespaces.findByPrefix(prefix);
   if (ns == null) return null;
   return ns.getName();
 }
 @Override
 protected CloseableIteration<? extends Namespace, SailException> getNamespacesInternal()
     throws SailException {
   Collection<? extends Namespace> ns = namespaces.getNamespacesWithPrefix();
   return new NamespaceIteration(ns.iterator());
 }
 @Override
 protected void clearNamespacesInternal() throws SailException {
   namespaces.clearPrefixes();
 }