Class Diagram

Information Systems Analysis and Design

CSC340

III. Class and Object Diagrams

Classes, Attributes and Operations

Objects and Multi-objects

Generalization and Inheritance

Associations and Multiplicity

Aggregation and Composition

How to Use Class Diagrams

© 2001 Jaelson Castro and John Mylopoulos

Class Diagrams -- 1

Information Systems Analysis and Design

CSC340

Classes

A class describes a group of objects with

similar properties (attributes),

common behaviour (operations),

common relationships to other objects,

and common meaning (“semantics”).

For example, “employee: has a name, employee# and

department; an employee is hired, and fired; an employee

works in one or more projects”

©2003 John Mylopoulos

Class Diagrams -- 2

Information Systems Analysis and Design

CSC340

Finding Classes

Finding classes in use case, or in text descriptions:

Look for nouns and noun phrases in the description of a use

case or a problem statement;

These are only included in the model if they explain the nature

or structure of information in the application.

Don’t create classes for concepts which:

Are beyond the scope of the system;

Refer to the system as a whole;

Duplicate other classes;

Are too vague or too specific (few instances);

Finding classes in other sources:

Reviewing background information;

Users and other stakeholders;

Analysis patterns;

CRC (Class Responsibility Collaboration) cards.

©2003 John Mylopoulos

Class Diagrams -- 3

Information Systems Analysis and Design

CSC340

StaffMember Class for Agate

For example, we may want to represent the concept of a staff

member for a company such as Agate in terms of the class

StaffMember.

StaffMember

Attributes

(optional)

Name (mandatory)

staffName

CalculateBonus()

ChangeGrade()

©2003 John Mylopoulos

Operations

(optional)

Class Diagrams -- 4

Information Systems Analysis and Design

CSC340

Names

Every class must have a unique...