Aggregation vs Composition in Object-Oriented Databases

1. Definition

Aggregation and Composition are two types of associations in object-oriented databases that define relationships between objects. Understanding these concepts is crucial for effective data modeling.

2. Key Concepts

3. Code Examples

3.1 Aggregation Example

class Book {
    String title;
    String author;

    Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
}

class Library {
    List books = new ArrayList<>();

    void addBook(Book book) {
        books.add(book);
    }
}
            

3.2 Composition Example

class Room {
    String name;

    Room(String name) {
        this.name = name;
    }
}

class House {
    List rooms = new ArrayList<>();

    House() {
        // Rooms are created with the House
        rooms.add(new Room("Living Room"));
        rooms.add(new Room("Bedroom"));
    }
}
            

4. Best Practices

• Use Aggregation when the lifecycle of the child is independent of the parent.
• Use Composition when the child lifecycle is tied to the parent.
• Clearly define relationships to avoid ambiguity in the model.
• Document relationships in the code for better maintainability.

5. FAQ