protected function flatImport($content, core_kernel_classes_Class $class)
    {
        $report = common_report_Report::createSuccess(__('Data imported successfully'));

        $graph = new EasyRdf_Graph();
        $graph->parse($content);

        // keep type property
        $map = [
            OntologyRdf::RDF_PROPERTY => OntologyRdf::RDF_PROPERTY
        ];

        foreach ($graph->resources() as $resource) {
            $map[$resource->getUri()] = common_Utils::getNewUri();
        }

        $format = EasyRdf_Format::getFormat('php');
        $data = $graph->serialise($format);

        foreach ($data as $subjectUri => $propertiesValues) {
            $resource = new core_kernel_classes_Resource($map[$subjectUri]);
            $subreport = $this->importProperties($resource, $propertiesValues, $map, $class);
            $report->add($subreport);
        }

        return $report;
    }