OOA&D Overview

📘 OOAD Overview (Object-Oriented Analysis & Design)

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🔹 1. Definition

Object-Oriented Analysis and Design (OOAD) is a software development approach that focuses on analyzing and designing a system using objects and classes.

• Object-Oriented Analysis (OOA): Understanding the problem domain
• Object-Oriented Design (OOD): Creating the solution/design

👉 Simple idea: OOAD helps you go from “What is needed?” → “How will it be built?”

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🔹 2. Key Concepts in OOAD

• Object: Real-world entity (e.g., Student, Car)
• Class: Blueprint of objects
• Attributes: Data of objects
• Methods: Behavior/functions
• Relationships: How objects interact

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🔹 3. Phases of OOAD ⭐

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🔸 3.1 Object-Oriented Analysis (OOA)

Goal: Understand requirements and identify key objects.

🔹 Steps:

1. Identify actors (users or external systems)
2. Identify use cases (what system should do)
3. Identify objects/classes
4. Define relationships

Output:

• Use Case Diagram
• Conceptual Class Diagram

Example: Library system → Actors: Member, Librarian

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🔸 3.2 Object-Oriented Design (OOD)

Goal: Transform analysis into a detailed design.

🔹 Steps:

1. Define class structure
2. Add attributes and methods
3. Design interactions
4. Apply design principles

Output:

• Detailed Class Diagrams
• Sequence Diagrams
• Activity Diagrams

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🔹 4. OOAD Process Flow

Requirements → Analysis → Design → Implementation → Testing

👉 OOAD mainly focuses on Analysis + Design

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🔹 5. Important OOAD Models (UML Diagrams)

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🔸 5.1 Use Case Diagram

• Shows interaction between actors and system

Diagram Description: Stick figures (actors) connected to oval shapes (use cases)

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🔸 5.2 Class Diagram

• Shows classes, attributes, methods, relationships

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🔸 5.3 Sequence Diagram

• Shows object interactions over time

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🔸 5.4 Activity Diagram

• Shows workflow or process flow

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🔸 5.5 State Diagram

• Shows state changes of an object

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🔹 6. Principles Used in OOAD

• Abstraction → Focus on essential features
• Encapsulation → Hide data
• Inheritance → Reuse code
• Polymorphism → Many forms

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🔹 7. Example (Library System)

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🔹 Analysis Phase:

• Actors: Member, Librarian
• Use Cases: Issue Book, Return Book

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🔹 Design Phase:

Class: Book
- title
- author
+ issue()
+ return()

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🔹 Interaction:

Member → requestBook() → Librarian → issueBook()

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🔹 8. Advantages of OOAD

• Better system understanding
• Reusability
• Easy maintenance
• Scalability
• Real-world mapping

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🔹 9. OOAD vs Traditional Approach

Feature	OOAD	Traditional
Focus	Objects	Functions
Reuse	High	Low
Flexibility	High	Limited

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🔹 10. Key Rules / Guidelines

• Identify real-world objects first
• Keep design modular
• Use UML diagrams
• Maintain low coupling & high cohesion
• Refine design iteratively

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🔹 11. Likely Exam Questions

1. Define OOAD and explain its importance.
2. Differentiate between OOA and OOD.
3. Explain phases of OOAD.
4. What are UML diagrams? Explain types.
5. Describe the OOAD process flow.
6. Explain use case diagram with example.
7. What is class diagram?
8. Advantages of OOAD over traditional methods.
9. Explain role of objects in OOAD.
10. Draw and explain sequence diagram.

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🔹 12. Quick Revision Summary 🧠

• OOAD = Analysis + Design using objects
• OOA → What system should do
• OOD → How system will work
• Uses UML diagrams
• Based on 4 pillars of OOP

👉 Shortcut Trick: "AD → Analyze then Design"

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