public function classLookUp($identifier, &$createdClasses)
    {
        $targetClass = false;
        foreach ($this->getClassLookUp() as $classLookup) {
            if ($this->hasMetadataValue($identifier)) {
                \common_Logger::i(__('Target Class Lookup for resource "%s"...', $identifier));
                if (($targetClass = $classLookup->lookup($this->getMetadataValue($identifier))) !== false) {
                    \common_Logger::i(__('Class Lookup Successful. Resource "%s" will be stored in RDFS Class "%s".',
                        $identifier, $targetClass->getUri()));

                    if ($classLookup instanceof MetadataClassLookupClassCreator) {
                        $createdClasses = $classLookup->createdClasses();
                    }

                    break;
                }
            }
        }
        return $targetClass;
    }