Bank describes a institution created by a author (user) to issue checks for users that reviewed his books.

Book is a single book.

BookError contains a single error that was informed by a user about a certain book.

Check is issued when a author approve a revision given by any user.

Genre describes a genre or category of book.

User is a single user.

UserType Represent a Type of User, being for the present moment "Reviewer" or "Author".