Object-Oriented Design in Software Engineering
Introduction
Object-Oriented Design (OOD) views a software system as a collection of objects—entities that combine data and behavior. In this approach, each object maintains its own state and provides methods to operate on that state.
For example, in a Library Automation System, each library member could be an individual object, with attributes (like name, ID, and borrowed books) and methods (such as borrowBook() or returnBook()) unique to them. Objects operate independently—one object’s methods cannot directly change another’s data.
Objects that share similar properties are grouped into classes, and classes can inherit features from more general superclasses, allowing code reusability and extensibility.
Key Concepts in Object-Oriented Design
1. Objects
Objects represent real-world entities involved in the solution. Examples include Person, Bank, Company, or User.
Each object has:
- Attributes – properties describing its state.
- Methods – functions that operate on its attributes.
2. Classes
A class is a blueprint for objects.
- An object is an instance of a class.
- A class defines what attributes and methods its objects will have.
3. Messages
Objects interact by sending messages to one another.
A message typically contains:
- The target object.
- The operation to be performed.
- Any required parameters.
In practice, this is implemented as function or procedure calls.
4. Abstraction
Abstraction means focusing on essentials and hiding unnecessary details.
- Helps manage complexity by ignoring irrelevant information.
- Lets developers concentrate on the important aspects of a problem.
5. Encapsulation
Encapsulation, also known as information hiding, binds data and the methods that operate on it into a single unit.
- Prevents direct access to an object’s internal state from the outside.
- Improves modularity and security of the code.
6. Inheritance
Inheritance allows classes to be arranged in a hierarchy, enabling subclasses to reuse attributes and methods from their parent classes.
- Promotes code reuse.
- Supports both generalization (broad concepts) and specialization (specific implementations).
7. Polymorphism
Polymorphism allows methods with the same name to perform different tasks depending on the context or parameters.
- Enables a single interface to work with different data types.
- Simplifies code while maintaining flexibility.
Conclusion
Object-Oriented Design helps create modular, reusable, and maintainable software by modeling real-world entities as objects. Through concepts like abstraction, encapsulation, inheritance, and polymorphism, developers can build systems that are both flexible and scalable, making OOD one of the most widely adopted software design approaches today.
