public function readDirectedPair()
    {
        try {
            return new QtiDirectedPair($this->readString(), $this->readString());
        } catch (BinaryStreamAccessException $e) {
            $msg = "An error occured while reading a directedPair.";
            throw new QtiBinaryStreamAccessException($msg, $this, QtiBinaryStreamAccessException::DIRECTEDPAIR, $e);
        }
    }