1Introduction to OOAD
- 1. Introduction to OOAD Lecture # 1 Ms. Shazia Yousaf Lecturer, Department of computer science, University of Sargodha Mandi Bahauddin Campus
- 2. OO Objectives We want a development method which: Is able to guide us through analysis, design, and implementation using one consistent paradigm throughout those phases Is less likely to generate errors Facilitates reuse of designs and code
- 3. Analysis & Design Analysis Investigation of problem and requirements, rather than a solution. E.g. Requirements analysis and OO analysis. Design It emphasizes a conceptual solution that fulfills the requirements. E.g. Database design or OO design Implementation expresses the true and complete realized design
- 4. Object Oriented Analysis (OOA) OOA is “a method of analysis that examines requirements from the perspectives of the classes and objects.” (Booch 1995) Emphasis is on finding and describing conceptual objects in the problem domain.
- 5. Object Oriented Design (OOD) OOD is “a method of design encompassing the process of OO decomposition and a notation for depicting both logical and physical as well as static and dynamic models of the system.” (Booch 1995) Emphasis is on defining software objects, and how they collaborate to fulfill system requirements
- 6. What is OO analysis and design? Essence of OO analysis - consider a problem domain from the perspective of objects (real world things, concepts) Essence of OO design - define the solution as a collection of software objects (allocating responsibilities to objects)
- 7. Examples- Library IS OO Analysis - in the case of the library information systems, one would find concepts like book, library, patron OO Design - emphasis on defining the software objects; ultimately these objects are implemented in some programming language; Book may have a method named print.
- 8. Example - contd. Book title public class Book { private String title; public ChaptergetChapter(int){...} } domain concept visualization of domain concept representation in an object-oriented programming language
- 9. Flight IS Plane tailNumber public class Plane { private String tailNumber; public List getFlightHistory() {...} } domain concept visualization of domain concept representation in an object-oriented programming language
- 10. What are the business processes? First step - consider what the business must do; in the case of a library - lending books, keeping track of due dates, buying new books. In requirements analysis; represent the business processes in textual narration (Use Cases).
- 11. Business processes - contd. Identifying and recording the business processes as use cases is not actually an object oriented activity; though a necessary first step.
- 12. Roles in the organization Identify the roles of people who will be involved in the business processes In OO terms - domain analysis Examples - customer, library assistant, programmer, navigator, sensor, etc.
- 13. Who does what? Business processes and roles (actors); time to determine how to fulfill the processes and who does these processes in OO terms - object oriented design; assigning responsibilities to the various software objects often expressed in class diagrams
- 14. In Summary... Business Analogy OO Analysis and Design Associated Documents What are the business processes? Requirements analysis Use cases What are employee roles? Domain analysis Conceptual model Who is responsible for what? Responsibility assignment; Design class diagrams
- 15. Simple example to see big picture Define use cases Define domain model Define interaction diagrams Define design class diagrams Define domain model Define Interaction diagrams Define design class diagrams Define use cases
- 16. Short Example Dice game A software simulates a player rolling two dice. If the total is seven, they win; otherwise, they lose.
- 17. Define use cases Use cases Narrative descriptions of domain processes in a structured prose format They are stories or scenarios of how people use the system Use case: Play a game Actors: Player Description: Player requests to roll the dice. System presents results: If the dice face value totals seven, player wins; otherwise, player loses.
- 18. Define conceptual model OO Analysis concerns specification of the problem domain identification of concepts (objects) Decomposition of the problem domain includes identification of objects, attributes, associations results can be expressed in conceptual model
- 19. Conceptual model - dice game Conceptual model is not a description of the software components; it represents concepts in the real world problem domain Player name DiceGame Die faceValue Rolls Plays Includes 2 2 1 1 1 1
- 20. Defining Interaction diagram OO Design is concerned with defining software objects – their responsibilities and collaborations Essential step - allocating responsibility to objects and illustrating how they interact with other objects Expressed as interaction diagrams Sequence Diagrams Communication Diagrams
- 21. Example – Sequence Diagram :DiceGame play() die1 :Die fv1 := getFaceValue() die2 :Die roll() roll() fv2 := getFaceValue()
- 22. Defining class diagrams Key questions to ask How do objects connect to other objects? What are the behaviors (methods) of these objects? interaction diagrams suggests connections; to support these connections methods are needed Expressed as class diagrams
- 23. Example - Class diagram 2 Die faceValue :int getFaceValue():int roll() DiceGame die1 :Die die2 :Die play() 1