private function _lookupDB($ua)
    {
        $browser = new Browser();
        $browser->setGrade(Grades::UNSUPPORTED);

        $conn = new \Mongo('mongodb://'.DeviceManager::HOST);
        $collection = $conn->selectDB(DeviceManager::DB)->devices;

        // Determine Regex fitting the U/A Category. 
        $pattern = $this->_getMatchingRegex($ua);
        $uaRegex = new \MongoRegex($pattern);

        //$device = $collection->findOne(array("userAgent"=>$nameRegex));
        // Match User Agent independent of OS Version, Check OS Version >= Base Matching Version
        $device = $collection->findOne(
            array (
                '$and'=>array (
                    array ("userAgent"=>$uaRegex), 
                    array ('$or'=> array(
                        array("device.os.version"=>array('$exists'=>false)),
                        array("device.os.version"=>array('$lte'=>"".$ua->osVersion))
                    ))
                )
            )
        );

        if (!empty($device)) {
            $browser = $this->_createBrowser($device);
        } else {
            // TODO : Request for Browser Categorization 
        }
        return $browser;
    }