Refine the Class Diagram


Now is the time to complete our class diaram. We will analyze every class gained from previous analysis.

It is obvious to have a deleting process invert to the creation process. This is said because in almost every class we have a creatind operation (in Object Oriented programming known as constructor), therefore an operation for deleting an object must be obtained in every class (in Object Oriented programming this is known as destructor).

A new attributes must be added for a Member class. They are alias, password and status. Alias and password will serve as an attributes for logging onto the system. It is obvious that Internet interface will allow a lot of people to access the Digital Library, but only those who have contracted membership with the library, can browse the data, make reservations and printing the electronic items. The Status attribute is introduced to distinguish between ordinary member and library employee-member. We said that every employee also can be a member of a library.

New operations for the Item class can be introduced according to the previous use case analysis. This operations are findOutTheOldestReservation(), checkForReservation() and receiveNumberOfReservations(), and they are described in previous lesson.

If we take a look at Member class attributes, Employee class attributes and an Author class atributes, we'll see that most of them are comon for these three classes. Therefore an inheritance may be introduced. We will create hew class Person wich will hold name, lastname and date of birdth attributes.

Description for classes is not longer necessary, because you are going to see all the classes with their last and final state. They are presented in the following list of classes.

class-person

class-lending

The Lending class

class-multimedia3.GIF (658 bytes)
The parent class Person with it's children The Multimedia class
class-item class-employee
class-reservation
The Reservation class
class-sample
The Item class hierarchy The Employee class and it's children
The Sample class

Click Here to see associations between these classes!