# File lib_wpm/wpm.rb, line 3652
    def start_element(ns_uri, prefix, name, attr_map)
      @depth += 1
      case (ns_uri)
      when XMLNS_DOC_URI
        case (name)
        when 'widget'
          widget_id = attr_map['name']
          unless (widget_id) then
            raise WidgetBindingError, 'not found a name attribute'
          end
          widget =  @widget_locator.create_widget(widget_id)
          unless (widget) then
            raise WidgetBindingError, "not found a widget: #{widget_id.inspect}"
          end
          @stack.last.add(widget)
          @stack.push(widget)
        when 'import'
          if (@depth != 1) then
            raise WidgetBindingError, "not a root element: #{name}@#{ns_uri}"
          end
        else
          raise WidgetBindingError, "unknown element: #{name}@#{ns_uri}"
        end
      else
        element = Element.new(ns_uri, prefix, name, attr_map)
        @stack.last.add(element)
        @stack.push(element)
      end

      nil
    end