Inheritance Case Studies in Object-Oriented Databases

1. Introduction

Inheritance is a fundamental concept in object-oriented databases, enabling the creation of hierarchical relationships between classes. This lesson explores various case studies illustrating the application and benefits of inheritance within object-oriented databases.

2. Key Concepts

2.1 Definition of Inheritance

Inheritance allows a new class (subclass) to inherit properties and methods from an existing class (superclass), promoting code reusability and organization.

2.2 Types of Inheritance

Single Inheritance
Multiple Inheritance
Multilevel Inheritance
Hierarchical Inheritance
Hybrid Inheritance

3. Case Studies

3.1 Case Study: University Database

In a university database, we can model entities such as Person, Student, and Faculty using inheritance:

class Person {
    String name;
    String address;
}

class Student extends Person {
    String studentId;
    String major;
}

class Faculty extends Person {
    String facultyId;
    String department;
}

3.2 Case Study: E-commerce System

In an e-commerce application, different types of users can inherit from a common User class:

class User {
    String username;
    String password;
}

class Customer extends User {
    String shippingAddress;
}

class Admin extends User {
    String adminLevel;
}

4. Best Practices

Use inheritance to promote code reuse but avoid overusing it as it can lead to complex hierarchies.
Prefer composition over inheritance when possible to enhance flexibility.
Keep the inheritance tree shallow to avoid complications in understanding relationships.
Document inheritance relationships clearly to aid in maintenance and understanding.

5. FAQ

What is the difference between inheritance and composition?

Inheritance defines a "is-a" relationship while composition describes a "has-a" relationship. Composition allows for more flexibility and reuse.

Can a class inherit from multiple classes?

In languages that support multiple inheritance, a class can inherit from more than one class. However, it can lead to ambiguity and is not universally supported.