final public function getReservedKeywordsList()
    {
        // Check for an existing instantiation of the keywords class.
        if ($this->_keywords) {
            return $this->_keywords;
        }

        $class    = $this->getReservedKeywordsClass();
        $keywords = new $class();
        if (! $keywords instanceof KeywordList) {
            throw DBALException::notSupported(__METHOD__);
        }

        // Store the instance so it doesn't need to be generated on every request.
        $this->_keywords = $keywords;

        return $keywords;
    }