1. Object Orientation An alternative approach to systems development
No longer a fad
Includes concepts, tools, methodologies and languages
Represents a fundamentally different way of looking at systems and breaking them down into parts

2. What is an object? An object has both data and operations
An object’s data is the information about the object
An object’s operations represent things that happen that affect the object’s data
This is called encapsulation
An object represents a major element of the system
Merges the process-driven and data-driven perspectives

3. Example: Banking Object Customer Object Account data: operations:
Name = “Joe Smith”
Address = “434 Maple St., Metro City, MD 92388”
operations:
new_customer
change_address
delete_customer
Object Account
data:
AccountNumber =
DateOpened = “12/15/1998”
CurrentBalance =
AccountType = “checking”
operations:
new_account
make_deposit
make_withdrawal
close_account

4. Instantiation
Class = a collection of objects, all of which have the same set of attributes (different values) and operations
The objects that belong to a class are called instances of that class
The class is instantiated when an object of that class is created
Example: Joe Smith is an instance of Customer

5. Specialization and Generalization
Classes can form a hierarchy, where more general classes are specialized into more specific classes
Example: The class Student can be specialized into the classes Undergraduate Student and Graduate Student
Example: The classes Frozen Food, Canned Food, and Perishable Food can be generalized into the class Food Item

6. Specialization and Generalization
Student
Food Item
Frozen
Food
Perishable
Food
Undergraduate
Student
Graduate
Student
Canned
Food

7. Inheritance
A child class inherits all its parent’s attributes and operations
A child class can also have other attributes and operations that did not come from the parent
A child class can override an inherited operation with another operation with the same name - one form of polymorphism

8. OO Tools for Analysis & Design
Use cases - scenarios that describe user’s requirements from the user’s point of view
Class diagram - defines the class hierarchy
State diagram - defines the events that affect objects
Sequence diagram - the logical design of a use case

9. Use Cases
Each use case represents a complete scenario describing how the system is used by some actor
An actor represents a role that a user plays; one user can play several roles
Use case scenarios are initiated by the actor, and can involve more than one actor
There can be relationships between use cases

10. << extends >>
Use Case Diagram
Rent video
Return video
Video
Store
Clerk
Video
Store
Customer
<< extends >>
Calculate
late fees

11. Class Diagrams Similar to ER diagrams, except operations are added
Classes are like entities
Attributes are the same concept
Associations are like relationships
Operations are new
Shows the hierarchy of classes and their specializations and generalizations

12. Class Diagram Examples
Account
Customer
Account#
DateOpened
CurrentBalance
AccountType
new_account
make_deposit
make_withdrawal
close_account
Name
Address
new_customer
change_address
delete_customer
Owns
1..*
0..*
owner
owner_type

13. Class Diagram Examples
Medical Complaint
description
Diagnose()
Gastrointestinal
foodDiary
Upper Respiratory
coughType
Muscular/Skeletal
areaOfBody
Other Complaint

14. Class Diagram Examples
PhotoEquipment
Model#
price
make
Test()
Lens
Test(Camera)
Camera
filmType
Test(Lens, Flash)
0..*
Flash
1..*
1..*
1..*
0..*
fits
uses
Test(Camera)
0..*
requires
quantity
requires
quantity
Battery
size
type
0..1
0..1

15. State Diagrams
A state of an object is some condition that it satisfies; most objects have many possible states, but they are in only one state at a time
An event is something that occurs at a specified point in time that changes an object’s state
A state transition is when an object changes from one state to another as a result of an event

16. State Diagram Example Customer Prospective Current Former
Makes purchase /
LastPurchaseDate = CurrentDate
Makes
inquiry
Prospective
6 months
Current
Makes purchase /
LastPurchaseDate = CurrentDate
[CurrentDate - LastPurchaseDate > 1 year]
Former
3 years
Makes purchase /
LastPurchaseDate = CurrentDate

17. Rapid Application Development
Motivated by the need for shorter development cycles
A general strategy for developing systems faster, not a specific methodology or technique
Appropriate when the number one concern is to produce a system quickly

18. Basic RAD Concepts Streamlining the SDLC process User involvement
combining phases
eliminating iteration
User involvement
helps ensure quick acceptance at end
helps eliminate iteration
Integrated CASE tools
rapid prototyping
minimizing effort to transform prototype to working system

19. Tools used in RAD Prototyping Code generation
quickly design and generate parts of interface
Code generation
eliminates need for handwriting source code
generates software from a design
Visual development environments
facilitates coding, especially implementing GUI interfaces
JAD

20. RAD Advantages Products developed more quickly
End product is more closely aligned with user needs because of less time between requirements and delivery
Often lower costs
System more aligned with user needs
Makes it possible to produce systems in rapidly changing environments

21. RAD Disadvantages Quality often suffers
interface consistency lacking
no adherence to standards
reusability and maintainability
No time for in-depth understanding of the organizational environment
risk of a major mismatch that is not understood until the end of the process
High dependence on user’s willingness to be involved throughout the process