private function getJSONVersionOfSchema()
    {
        // Set cachefile
        $cacheFile = dirname(dirname(__DIR__)) . '/data/schemaorg.cache';

        if (!file_exists($cacheFile)) {
            // Create dir
            if (!file_exists(dirname($cacheFile))) {
                mkdir(dirname($cacheFile), 0777, true);
            }

            // Load RDFA Schema
            $graph = new \EasyRdf_Graph(self::RDFA_SCHEMA);
            $graph->load(self::RDFA_SCHEMA, 'rdfa');

            // Lookup the output format
            $format = \EasyRdf_Format::getFormat('jsonld');

            // Serialise to the new output format
            $output = $graph->serialise($format);

            if (!is_scalar($output)) {
                $output = var_export($output, true);
            }

            $this->schema = \ML\JsonLD\JsonLD::compact($graph->serialise($format), 'http://schema.org/');

            // Write cache file
            file_put_contents($cacheFile, serialize($this->schema));
        } else {
            $this->schema = unserialize(file_get_contents($cacheFile));
        }
    }