A library application (complete user requirements)

The goal for the next weeks is to implement parts of the software supporting the management of a public library. The library contains books, DVDs and CDs, and journals. Books, DVDs and CDs can be borrowed from any user registered with the library. Books can be borrowed for a period of at most 4 weeks; DVDs and CDs only for a period of one week; and journals can't be borrowed at all.