Each manufacturer manufactures many disk-drives, and the manufacturer assigns each disk-drive a serial number. The serial number is unique within a manufacturer, but not across all other manufacturers. The manufacturer registers the model of the disk-drive it produces to the intellectual property Office of Singapore (IPOS) so that the model of the disk drive is protected and cannot be used by other manufacturer. The disk-drives are manufactured by batch, and all the disk-drives manufactured in a batch are of the same model, and all the disk- drives of the same model have the same capacity. A distributor collaborates with many manufacturers to help the manufacturers to distribute the disk-drives the distributor receives to retailers. A distributor creates a relational table DISK_DRIVE to store the information/attributes of the disk drive it distributes to retailers as follows: DISK_DRIVE(serialNum, manufacturer, model, batch, capacity, retailer)