Requirements and use cases in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the primary actor in a use case.

LLD

The primary actor in a use case is the [1] who initiates the interaction.

Drag options to blanks, or click blank then click option'

Asystem

Bserver

Cuser

Ddatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the system with the actor.

Choosing internal components like database as actors.

The primary actor is the user who starts the use case interaction.

2fill in blank

medium

Complete the code to specify the main goal of a use case.

LLD

The main goal of a use case is to [1] a specific function or service for the actor.

Drag options to blanks, or click blank then click option'

Adelay

Bdescribe

Cignore

Dachieve

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'describe' instead of 'achieve' as the goal.

Selecting negative actions like 'ignore' or 'delay'.

The main goal is to achieve a function or service that the actor needs.

3fill in blank

hard

Fix the error in the use case description by completing the blank.

LLD

A use case should include [1] to handle exceptions and errors.

Drag options to blanks, or click blank then click option'

Aalternate flows

Bscenarios

Cactors

Ddiagrams

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing scenarios with alternate flows.

Choosing actors or diagrams which do not handle errors.

Alternate flows describe how the system handles exceptions and errors.

4fill in blank

hard

Fill both blanks to complete the use case template fields.

LLD

Use case name: [1]
Primary actor: [2]

Drag options to blanks, or click blank then click option'

ALogin

BSystem

CUser

DDatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping actor and use case name.

Choosing system or database as primary actor.

The use case name is 'Login' and the primary actor is the 'User'.

5fill in blank

hard

Fill all three blanks to complete the use case description.

LLD

Precondition: [1]
Trigger: [2]
Postcondition: [3]

Drag options to blanks, or click blank then click option'

AUser is logged out

BUser clicks login button

CUser is logged in

DSystem is offline

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing precondition and postcondition.

Choosing system offline as a trigger.

The precondition is that the user is logged out, the trigger is clicking the login button, and the postcondition is the user is logged in.

Practice

1. What is the main purpose of requirements in system design?

easy

A. To write the system's source code

B. To describe how users interact with the system

C. To design the user interface layout

D. To specify what the system must do

Solution

1. Step 1: Understand the definition of requirements

   Requirements define the functions and features the system must provide.

2. Step 2: Differentiate from use cases

   Use cases describe user interactions, not the system's core functions.

3. Final Answer:

   To specify what the system must do -> Option D

4. Quick Check:

   Requirements = system functions [OK]

Hint: Requirements = what system must do, not how users act [OK]

Common Mistakes:

• Confusing requirements with use cases
• Thinking requirements include UI design
• Assuming requirements are code instructions

2. Which of the following best describes a use case in system design?

easy

A. A scenario showing user interaction with the system

B. A code module for user authentication

C. A diagram of system architecture

D. A detailed list of system features

Solution

1. Step 1: Define use case

   A use case is a story or scenario describing how a user uses the system.

2. Step 2: Eliminate unrelated options

   System features list, architecture diagrams, and code modules are not use cases.

3. Final Answer:

   A scenario showing user interaction with the system -> Option A

4. Quick Check:

   Use case = user scenario [OK]

Hint: Use case = user story or interaction example [OK]

Common Mistakes:

• Mixing use cases with system features
• Confusing use cases with technical diagrams
• Thinking use cases are code components

3. Given a system that allows users to upload photos and comment, which of the following is a valid use case?

medium

A. System stores photos in a database

B. User uploads a photo and receives confirmation message

C. Database schema includes photo metadata fields

D. Server runs a nightly backup process

Solution

1. Step 1: Identify user actions in options

   User uploads a photo and receives confirmation message describes a user action and system response, fitting a use case.

2. Step 2: Recognize system internals vs user interaction

   Options A, C, and D describe internal system details, not user interactions.

3. Final Answer:

   User uploads a photo and receives confirmation message -> Option B

4. Quick Check:

   User action + system response = use case [OK]

Hint: Use case = user action plus system reaction [OK]

Common Mistakes:

• Choosing system internal processes as use cases
• Ignoring the user perspective
• Confusing data storage details with use cases

4. A system design document lists: "Users can reset passwords via email." Which of the following is a problem in this use case description?

medium

A. It includes too much technical detail about email servers

B. It lacks the steps describing how users reset passwords

C. It incorrectly describes a system requirement instead of a use case

D. It is missing the database schema for password storage

Solution

1. Step 1: Analyze the use case description

   The statement is a high-level feature but lacks detailed user steps.

2. Step 2: Understand use case completeness

   Use cases should describe user actions step-by-step, not just state features.

3. Final Answer:

   It incorrectly describes a system requirement instead of a use case -> Option C

4. Quick Check:

   Use case needs detailed user steps [OK]

Hint: Use cases must show user steps, not just features [OK]

Common Mistakes:

• Confusing requirements with use cases
• Expecting technical details in use cases
• Ignoring the need for step-by-step user actions

5. You are designing a ride-sharing app. Which of the following best combines requirements and use cases for the feature "Request a ride"?

hard

A. Requirement: The system must match riders with drivers within 2 minutes. Use case: Rider opens app, enters destination, and confirms ride request.

B. Requirement: The app must have a blue color theme. Use case: Driver updates profile picture.

C. Requirement: The system stores all ride data for 1 year. Use case: Admin views system logs.

D. Requirement: The app sends promotional emails weekly. Use case: Rider rates driver after ride.

Solution

1. Step 1: Identify relevant requirement for ride request

   Matching riders with drivers quickly is a key system requirement for this feature.

2. Step 2: Identify matching use case

   The use case describes the rider's interaction to request a ride step-by-step.

3. Step 3: Verify other options

   Other options mix unrelated requirements or use cases not tied to "Request a ride" feature.

4. Final Answer:

   Requirement: The system must match riders with drivers within 2 minutes. Use case: Rider opens app, enters destination, and confirms ride request. -> Option A

5. Quick Check:

   Requirement + user steps = correct combination [OK]

Hint: Match system needs with user steps for correct design [OK]

Common Mistakes:

• Mixing unrelated requirements and use cases
• Ignoring user interaction details
• Choosing cosmetic or admin features instead of core ones