The next step is to create a module
booksdb.py that uses the
relation modules to construct a data model that can be used conveniently by the delivery layer (the parts of the web application that deal with providing content to the client). We therefore have to define
Book, Author, and
User entities as well as a
BookAuthor relation and a
We will also provide some functions that are bit more high-level, for example, a
newbook() function that checks whether a book with a given title already exists and that only creates a new
Book instance if the authors are different (presumably because they wrote a book with the same title).
Having a separate layer that models data in terms ...