This exercise asks you to convert business statements into dependencies. Consider the relation DISK_DRIVE (Serial_number, Manufacturer, Model, Batch, Capacity, Retailer). Each tuple in the relation DISK_DRIVE contains information about a disk drive with a unique Serial_number, made by a manufacturer, with a particular model number, released in a certain batch, which has a certain storage capacity and is sold by a certain retailer. For example, the tuple Disk_drive (‘1978619', ‘Western Digital', ‘A2235X', ‘765234', 500, ‘CompUSA') specifies that Western Digital made a disk drive with serial number 1978619 and model number A2235X, released in batch 765234; it is 500GB and sold by CompUSA.
Write each of the following dependencies as an FD:
a. The manufacturer and serial number uniquely identifies the drive.
b. A model number is registered by a manufacturer and therefore can't be used by another manufacturer.
c. All disk drives in a particular batch are the same model.
d. All disk drives of a certain model of a particular manufacturer have exactly the same capacity.