protected function _checkRequiredOptions(array $config)
    {
        // we need at least a dbname
        if (! array_key_exists('dbname', $config)) {
            /** @see Zend_Db_Adapter_Exception */
            // require_once 'Zend/Db/Adapter/Exception.php';
            throw new Zend_Db_Adapter_Exception("Configuration array must have a key for 'dbname' that names the database instance");
        }

        if (! array_key_exists('password', $config) && array_key_exists('username', $config)) {
            /**
             * @see Zend_Db_Adapter_Exception
             */
            // require_once 'Zend/Db/Adapter/Exception.php';
            throw new Zend_Db_Adapter_Exception("Configuration array must have a key for 'password' for login credentials.
                                                If Windows Authentication is desired, both keys 'username' and 'password' should be ommited from config.");
        }

        if (array_key_exists('password', $config) && !array_key_exists('username', $config)) {
            /**
             * @see Zend_Db_Adapter_Exception
             */
            // require_once 'Zend/Db/Adapter/Exception.php';
            throw new Zend_Db_Adapter_Exception("Configuration array must have a key for 'username' for login credentials.
                                                If Windows Authentication is desired, both keys 'username' and 'password' should be ommited from config.");
        }
    }