public function addAllowedRole($role, $attribute = 'access')
    {
        $roleStr = (string) $role;
        if (!isset($this->allowedRoles[$roleStr])) {
            $this->allowedRoles[$roleStr] = array();
        }
        $this->allowedRoles[$roleStr][(string) $attribute] = true;
        return $this;
    }