Object Oriented Analysis and Design

INTRODUCTION:

Object-Oriented Analysis and Design (OOAD) is a software engineering methodology that involves using object-oriented concepts to design and implement software systems. OOAD involves a number of techniques and practices, including object-oriented programming, design patterns, UML diagrams, and use cases. Here are some important aspects of OOAD:

1. Object-Oriented Programming: Object-oriented programming involves modeling real-world objects as software objects, with properties and methods that represent the behavior of those objects. OOAD uses this approach to design and implement software systems.
2. Design Patterns: Design patterns are reusable solutions to common problems in software design. OOAD uses design patterns to help developers create more maintainable and efficient software systems.
3. UML Diagrams: Unified Modeling Language (UML) is a standardized notation for creating diagrams that represent different aspects of a software system. OOAD uses UML diagrams to represent the different components and interactions of a software system.
4. Use Cases: Use cases are a way of describing the different ways in which users interact with a software system. OOAD uses use cases to help developers understand the requirements of a system and to design software systems that meet those requirements.

There are several advantages to using OOAD in software engineering:

1. Reusability: OOAD emphasizes the use of reusable components and design patterns, which can save time and effort in software development.
2. Scalability: OOAD can help developers design software systems that are scalable and can handle changes in user demand and business requirements over time.
3. Maintainability: OOAD emphasizes modular design and can help developers create software systems that are easier to maintain and update over time.
4. Flexibility: OOAD can help developers design software systems that are flexible and can adapt to changing business requirements over time.
5. However, there are also some potential disadvantages to using OOAD:
6. Complexity: OOAD can be complex and may require significant expertise to implement effectively.
7. Time-consuming: OOAD can be a time-consuming process that involves significant upfront planning and documentation.
8. Rigidity: Once a software system has been designed using OOAD, it can be difficult to make changes without significant time and expense.
9. Cost: OOAD can be more expensive than other software engineering methodologies due to the upfront planning and documentation required.
10. Overall, OOAD can be an effective approach to designing and implementing software systems, particularly for complex or large-scale projects. However, it’s important to weigh the advantages and disadvantages carefully before adopting this approach.

Object-Oriented Analysis (OOA) is the first technical activity performed as part of object-oriented software engineering. OOA introduces new concepts to investigate a problem. It is based on a set of basic principles, which are as follows-

1. The information domain is modeled.
2. Behavior is represented.
3. The function is described.
4. Data, functional, and behavioral models are divided to uncover greater detail.
5. Early models represent the essence of the problem, while later ones provide implementation details.

The above notes principles form the foundation for the OOA approach. 

Object-Oriented Design (OOD): An analysis model created using object-oriented analysis is transformed by object-oriented design into a design model that works as a plan for software creation. OOD results in a design having several different levels of modularity i.e., The major system components are partitioned into subsystems (a system-level “modular”), and data manipulation operations are encapsulated into objects (a modular form that is the building block of an OO system.). In addition, OOD must specify some data organization of attributes and a procedural description of each operation. Shows a design pyramid for object-oriented systems. It is having the following four layers.

1. The Subsystem Layer : It represents the subsystem that enables software to achieve user requirements and implement technical frameworks that meet user needs.
2. The Class and Object Layer : It represents the class hierarchies that enable the system to develop using generalization and specialization. This layer also represents each object.
3. The Message Layer : It represents the design details that enable each object to communicate with its partners. It establishes internal and external interfaces for the system.
4. The Responsibilities Layer : It represents the data structure and algorithmic design for all the attributes and operations for each object.

The Object-Oriented design pyramid specifically emphasizes specific product or system design. Note, however, that another design layer exists, which forms the base on which the pyramid rests. It focuses on the core layer the design of the domain object, which plays an important role in building the infrastructure for the Object-Oriented system by providing support for human/computer interface activities, task management.

Some of the terminologies that are often encountered while studying Object-Oriented Concepts include:

1. Attributes: a collection of data values that describe a class.

2. Class: encapsulates the data and procedural abstractions required to describe the content and behavior of some real-world entity. In other words,  A class is a generalized description that describes the collection of similar objects.

3. Objects: instances of a specific class. Objects inherit a class’s attributes and operations.

4. Operations: also called methods and services, provide a representation of one of the behaviors of the class.

5. Subclass: specialization of the super class. A subclass can inherit both attributes and operations from a super class.

6. Superclass:  also called a base class, is a generalization of a set of classes that are related to it.

Advantages of OOAD:

1. Improved modularity: OOAD encourages the creation of small, reusable objects that can be combined to create more complex systems, improving the modularity and maintainability of the software.
2. Better abstraction: OOAD provides a high-level, abstract representation of a software system, making it easier to understand and maintain.
3. Improved reuse: OOAD encourages the reuse of objects and object-oriented design patterns, reducing the amount of code that needs to be written and improving the quality and consistency of the software.
4. Improved communication: OOAD provides a common vocabulary and methodology for software developers, improving communication and collaboration within teams.
5. Reusability: OOAD emphasizes the use of reusable components and design patterns, which can save time and effort in software development by reducing the need to create new code from scratch.
6. Scalability: OOAD can help developers design software systems that are scalable and can handle changes in user demand and business requirements over time.
7. Maintainability: OOAD emphasizes modular design and can help developers create software systems that are easier to maintain and update over time.
8. Flexibility: OOAD can help developers design software systems that are flexible and can adapt to changing business requirements over time.
9. Improved software quality: OOAD emphasizes the use of encapsulation, inheritance, and polymorphism, which can lead to software systems that are more reliable, secure, and efficient.

Disadvantages of OOAD:

1. Complexity: OOAD can add complexity to a software system, as objects and their relationships must be carefully modeled and managed.
2. Overhead: OOAD can result in additional overhead, as objects must be instantiated, managed, and interacted with, which can slow down the performance of the software.
3. Steep learning curve: OOAD can have a steep learning curve for new software developers, as it requires a strong understanding of OOP concepts and techniques.
4. Complexity: OOAD can be complex and may require significant expertise to implement effectively. It may be difficult for novice developers to understand and apply OOAD principles.
5. Time-consuming: OOAD can be a time-consuming process that involves significant upfront planning and documentation. This can lead to longer development times and higher costs.
6. Rigidity: Once a software system has been designed using OOAD, it can be difficult to make changes without significant time and expense. This can be a disadvantage in rapidly changing environments where new technologies or business requirements may require frequent changes to the system.
7. Cost: OOAD can be more expensive than other software engineering methodologies due to the upfront planning and documentation required.