public function activate($name = null)
    {
        if (!$this->sieve) {
            return $this->_set_error(self::ERROR_INTERNAL);
        }

        if (!$name) {
            $name = $this->current;
        }

        $result = $this->sieve->setActive($name);

        if (is_a($result, 'PEAR_Error')) {
            return $this->_set_error(self::ERROR_ACTIVATE);
        }

        $this->active = $name;

        return true;
    }