private function getNavigationElementsByGroup($groupId)
    {
        $entries = array();
        foreach (MenuService::getPerspectivesByGroup($groupId) as $i => $perspective) {
            $binding = $perspective->getBinding();
            $children = $this->getMenuElementChildren($perspective);

            if (!empty($binding) || !empty($children)) {
                $entry = array(
                    'perspective' => $perspective,
                    'children'    => $children
                );
                if (!is_null($binding)) {
                    $entry['binding'] = $perspective->getExtension() . '/' . $binding;
                }
                $entries[$i] = $entry;
            }
        }
        return $entries;
    }