Identifying classes from requirements in LLD - Architecture Diagram

System Overview - Identifying classes from requirements

This system helps to identify classes from given software requirements. It breaks down requirements into meaningful objects (classes) that represent real-world entities or concepts. The goal is to organize requirements into a clear structure for easier design and development.

Architecture Diagram

User
  |
  v
Requirement Parser
  |
  v
Class Identifier
  |
  v
Class Repository
  |
  v
Output Generator
  |
  v
User

Components

User

actor

Provides software requirements input and receives identified classes output

Requirement Parser

service

Analyzes raw requirements text to extract key nouns and verbs

Class Identifier

service

Determines candidate classes based on parsed requirements

Class Repository

database

Stores identified classes and their attributes

Output Generator

service

Formats and delivers the list of identified classes back to the user

Request Flow - 5 Hops

User → Requirement Parser

Requirement Parser → Class Identifier

Class Identifier → Class Repository

Class Identifier → Output Generator

Output Generator → User

Failure Scenario

Component Fails:Class Repository

Impact:Identified classes cannot be saved or retrieved, causing loss of data and inability to provide output

Mitigation:Use database replication and backups to ensure availability and data recovery

Architecture Quiz - 3 Questions

Which component first processes the raw requirements text?

A Output Generator

B Requirement Parser

C Class Identifier

D Class Repository

Design Principle

This architecture separates concerns by parsing requirements, identifying classes, storing them, and formatting output in distinct components. This modular design improves clarity, scalability, and maintainability.

Practice

1. Which of the following is most likely a class when designing a library management system?

easy

A. Return

B. Borrow

C. Book

D. Search

Solution

1. Step 1: Identify nouns in the requirement

   Classes usually come from nouns. Here, 'Book' is a noun representing an object.

2. Step 2: Differentiate between nouns and verbs

   'Borrow', 'Return', and 'Search' are actions (verbs), so they are methods, not classes.

3. Final Answer:

   Book -> Option C

4. Quick Check:

   Class = Noun = Book [OK]

Hint: Pick the noun as class, verbs become methods [OK]

Common Mistakes:

• Choosing verbs as classes
• Confusing actions with objects
• Ignoring nouns in requirements

2. In a ride-sharing app, which of these is the correct way to represent a class in code?

easy

A. class Driver {}

B. function Driver() {}

C. var Driver = 5;

D. let driver = 'John';

Solution

1. Step 1: Understand class syntax in LLD context

   Classes are defined with the keyword 'class' followed by the class name.

2. Step 2: Check options for class declaration

   class Driver {} uses 'class Driver {}' which is correct syntax for a class.

3. Final Answer:

   class Driver {} -> Option A

4. Quick Check:

   Class syntax uses 'class' keyword [OK]

Hint: Look for 'class' keyword to identify class declaration [OK]

Common Mistakes:

• Using function instead of class
• Assigning class name to variable
• Confusing variables with classes

3. Given the requirement: "A hotel booking system must manage Guests, Rooms, and Bookings." Which of these is the correct set of classes identified?

medium

A. [Booking, Book, GuestList]

B. [Guest, Room, Booking]

C. [Guest, Book, RoomBooking]

D. [Room, Guest, ReservationList]

Solution

1. Step 1: Extract nouns from the requirement

   The nouns are Guests, Rooms, and Bookings, which represent objects.

2. Step 2: Match nouns to class names

   Classes should be singular nouns representing entities: Guest, Room, Booking.

3. Final Answer:

   [Guest, Room, Booking] -> Option B

4. Quick Check:

   Classes = Nouns = Guest, Room, Booking [OK]

Hint: Pick singular nouns as class names from requirements [OK]

Common Mistakes:

• Using verbs as classes
• Using plural or combined names incorrectly
• Adding unrelated terms

4. You have a requirement: "The system should allow Users to login and logout." Which of the following is an error in identifying classes and methods?

medium

A. Class: User; Methods: login(), logout()

B. Class: UserAccount; Methods: login(), logout()

C. Class: User; Methods: authenticate(), logout()

D. Class: Login; Methods: user(), logout()

Solution

1. Step 1: Identify nouns and verbs

   'User' is a noun (class), 'login' and 'logout' are actions (methods).

2. Step 2: Check option correctness

   Class: Login; Methods: user(), logout() incorrectly uses 'Login' as a class and 'user()' as a method, which reverses noun and verb roles.

3. Final Answer:

   Class: Login; Methods: user(), logout() -> Option D

4. Quick Check:

   Class = noun, Method = verb [OK]

Hint: Classes are nouns; methods are verbs [OK]

Common Mistakes:

• Using verbs as classes
• Naming methods as nouns
• Mixing class and method roles

5. A food delivery app requirement states: "Customers place Orders, Restaurants prepare Meals, and DeliveryAgents deliver Orders." Which classes should be created to model this system correctly?

hard

A. [Customer, Order, Restaurant, Meal, DeliveryAgent]

B. [Customer, PlaceOrder, Restaurant, Meal, Deliver]

C. [CustomerOrder, RestaurantMeal, Delivery]

D. [Order, Meal, DeliveryAgent, Place]

Solution

1. Step 1: Identify all nouns in the requirement

   Nouns are Customers, Orders, Restaurants, Meals, DeliveryAgents.

2. Step 2: Use nouns as class names and verbs as methods

   Classes should be Customer, Order, Restaurant, Meal, DeliveryAgent. Actions like 'place' and 'deliver' become methods.

3. Final Answer:

   [Customer, Order, Restaurant, Meal, DeliveryAgent] -> Option A

4. Quick Check:

   Classes = Nouns only, verbs become methods [OK]

Hint: Classes = nouns; actions = methods in those classes [OK]

Common Mistakes:

• Using verbs as classes
• Combining nouns incorrectly
• Omitting important entities