code: @GET
      @Produces(MediaType.APPLICATION_XML)
      public StreamingOutput getRoot() {
          final List<String> resources = new ArrayList<String>();
          resources.addAll(Systems.getSystems().keySet());
          return ResponseBuilder.buildDOMResponse(resources);
      }
docs: This method waits for calls to the above specified URL {@link JaxRxConstants#ROOTPATH} and creates a
  response XML file containing
  the available further resources. In our case it is just the {@link JaxRxConstants#SYSTEMPATH} resource.
  
  @return The available resources according to the URL path.