A typical university library provides textbooks on various subjects to their students. A new database system is needed to maintain data on textbooks in the library and textbooks that have been ordered. After some initial investigations, the following details regarding various types of data have been found.

Details of a typical textbook include the names of author$($s$),$ the book title, edition number, the publisher name, the year of publication and the book$$s ISBN number $($NB: the ISBN number is unique to the book. Different editions of the same book have different ISBN numbers. However, different copies of the same book have the same ISBN number$).$ A textbook are either purchased from an online provider such as Amazon.com or directly from a publisher like Pearson Education. The library wishes to keep a record on the book providers $($such as name, website and contact telephone number$)$ for ordering new books.

Normally, several copies of the same textbook are ordered by the library to ensure that there are sufficient numbers of the book for multiple simuteneous accesses. When a book is displayed on shelf, each copy of the book is assigned an internal library book number unique to the copy. The book is also assigned with a shelf number in a subject section. For instance, a copy of Hongbo$$s book $$Data Mining Techniques and Applications, an Introduction$$ may be assigned a library code of COMHD$01$ on Shelf $11$ in the Computing section. A date that the copy becomes available should be recorded for future reference purposes. Each copy also has a status from time to time to indicate whether the copy is being borrowed, reserved, or available $($NB: details on readers who borrow or reserve books are not of interest till Part $($iv$)).$

A textbook is normally recommended by a module leader for supporting the learning of the module$$s subject. There are textbooks that can become general background reading without relating to a specific module. The library wants to know the module title, the module leader name, the term the module is taught, and the programme that the module belongs to$.$ A module can normally have several recommended textbooks, but one textbook is normally used for supporting one module. Over the years, the module content may change, and new editions of some textbooks and new textbooks may be recommended. It is therefore useful for the library to maintain a record on the starting and the ending yeard that a specific textbook $($or a specific edition$)$ has been used for a module.

$($i$)$ Use the scenario as a reference to outline the three main phases of top$-$down database design. Explain the purpose for each phase.

$($ii$)$ Analyze the data to be stored in terms of entity sets, relationship sets, their attributes and their properties and draw complete lists of them using the Entity$-$Relationship model.se for each phase.

$($iii$)$ Draw an entity$-$relationship diagram $($ERD$)$ as the conceptual schema of the database.

$($iv$)$ If the database needs to be expanded to include readers $($reader ID and name$)$ borrowing textbooks from the library with a borrowing date and a returning date, draw an updated ERD for the expanded conceptual schema $(15$ marks$).$ Does the expanded ERD have any connection traps? If yes, show where the connection trap appears and what type it belongs to$.$ If not, explain your reasons please.