code: @Override
      public void verify(Document d) throws SymbolWarning, IndexingFailure,
              ResourceDownloadError {
          final List<NamespaceSyntaxWarning> exceptions =
                  new ArrayList<NamespaceSyntaxWarning>();
  
          // open document namespaces if necessary
          for (Namespace ns : d.getAllNamespaces()) {
              String resourceLocation = ns.getResourceLocation();
  
              synchronized (resourceLocation) {
                  if (!isOpen(resourceLocation)) {
                      final String indexPath = doCompile(resourceLocation);
                      openNamespace(resourceLocation, indexPath);
                  }
              }
          }
  
          for (final Parameter p : d.getAllParameters()) {
              Namespace ns = p.getNamespace();
              if (ns == null) {
                  continue;
              }
  
              try {
                  doVerify(p);
              } catch (NamespaceSyntaxWarning e) {
                  exceptions.add(e);
              }
          }
  
          if (!exceptions.isEmpty()) {
              final String name = d.getName();
              final String fmt = INVALID_SYMBOLS;
              final String msg = format(fmt, exceptions.size());
              throw new SymbolWarning(name, msg, exceptions);
          }
      }
docs: {@inheritDoc}