public function render()
    {
        // preload images
        $sHTML = "<script language=\"JavaScript\">\n".
                " minus = new Image();\n minus.src = \"".Openbizx::$app->getImageUrl()."/minus.gif\";\n".
                " plus = new Image();\n plus.src = \"".Openbizx::$app->getImageUrl()."/plus.gif\";\n".
                "</script>\n";

        // list all views and highlight the current view
        $sHTML .= "<ul class='expanded'>\n";
        $sHTML .= $this->renderNodeItems($this->nodesXml);
        $sHTML .= "</ul>";
        return $sHTML;
    }