Class diagrams in Software Engineering - Mini Project: Build & Apply

Understanding Class Diagrams

📖 Scenario: You are designing a simple system to manage a library. You want to represent the main parts of the system using a class diagram. This will help you understand how different parts relate to each other.

🎯 Goal: Create a basic class diagram showing classes, their attributes, and relationships for a library system.

📋 What You'll Learn

Create classes with names and attributes

Define a relationship between classes

Use correct notation for attributes and relationships

Show multiplicity for relationships

💡 Why This Matters

🌍 Real World

Class diagrams help software designers plan and communicate the structure of software systems clearly before coding.

💼 Career

Understanding class diagrams is essential for software engineers, system analysts, and architects to design maintainable and scalable software.

1

Create the basic classes

Create two classes named Book and Author. For Book, add attributes title and isbn. For Author, add attributes name and birthYear. Use the standard UML class diagram notation with class names in a box and attributes listed below the name.

Software Engineering

# Draw two class boxes labeled 'Book' and 'Author' with their attributes listed
# Your code here

Hint

Remember, in UML class diagrams, attributes are listed below the class name inside the class box.

2

Add a relationship between classes

Add an association relationship from Author to Book to show that an author writes books. Use a solid line with an arrow pointing from Author to Book. Label the relationship writes.

Software Engineering

class Book {
  + title: String
  + isbn: String
}

class Author {
  + name: String
  + birthYear: Integer
}

# Draw an association line from Author to Book labeled 'writes'
# Your code here

Hint

Use a solid line with an arrow and label it 'writes' to show the association.

3

Specify multiplicity on the relationship

Add multiplicity to the association to show that one Author can write many Book objects, and each Book is written by exactly one Author. Use 1 near Author and * near Book on the association line.

Software Engineering

class Book {
  + title: String
  + isbn: String
}

class Author {
  + name: String
  + birthYear: Integer
}

Author "1" --writes--> "*" Book
# Add multiplicity numbers near Author and Book
# Your code here

Hint

Multiplicity shows how many instances of one class relate to instances of another.

4

Add a new class and relationship

Add a new class called Library with an attribute name. Then add an association from Library to Book labeled contains. Show that a library can contain many books, but each book belongs to exactly one library. Use multiplicity 1 near Book and * near Library.

Software Engineering

class Book {
  + title: String
  + isbn: String
}

class Author {
  + name: String
  + birthYear: Integer
}

Author "1" --writes--> "*" Book

# Add class Library with attribute name
# Add association from Library to Book labeled 'contains' with multiplicity
# Your code here

Hint

Remember to add the new class box and draw the association line with correct multiplicity and label.