Use case diagrams in Software Engineering - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Actors in Use Case Diagrams

In a use case diagram, what does an actor represent?

A A detailed description of system requirements

B A specific function or feature of the system

C A graphical symbol used to connect use cases

D A system or external entity that interacts with the system

💡 Hint

Think about who or what communicates with the system from outside.

An actor in a use case diagram represents an external entity, such as a user or another system, that interacts with the system to achieve a goal.

📋 Factual

intermediate

Symbols Used in Use Case Diagrams

Which symbol is typically used to represent a use case in a use case diagram?

A Oval or ellipse

B Rectangle

C Triangle

D Diamond

💡 Hint

It looks like an egg shape or stretched circle.

Use cases are represented by ovals or ellipses to show the actions or services the system provides.

🔍 Analysis

advanced

Identifying Relationships in Use Case Diagrams

Consider a use case diagram where one use case includes another use case. What does this include relationship mean?

A The included use case is optional and may or may not be executed

B The included use case replaces the base use case entirely

C The base use case always calls the included use case as part of its process

D The two use cases are unrelated and independent

💡 Hint

Think about when the included use case happens during the base use case.

An include relationship means the base use case always executes the included use case as part of its steps.

❓ Comparison

advanced

Difference Between Extend and Include Relationships

What is the main difference between extend and include relationships in use case diagrams?

A Include is mandatory; extend is optional and happens only under certain conditions

B Extend is mandatory; include is optional and happens only under certain conditions

C Both are mandatory and always executed together

D Both are optional and never executed

💡 Hint

Consider when each related use case is executed.

Include means the included use case always runs; extend means the extending use case runs only if certain conditions are met.

❓ Reasoning

expert

Determining the Number of Use Cases in a Diagram

A use case diagram shows 3 actors and 5 use cases. Two use cases are connected by an extend relationship, and one use case includes another. How many unique use cases are represented in the diagram?

A 6

B 5

C 4

D 7

💡 Hint

Think about whether include or extend relationships add new use cases or just connect existing ones.

Include and extend relationships connect existing use cases; they do not add new unique use cases. So the total remains 5.

Practice

1. What is the main purpose of a use case diagram in software engineering?

easy

A. To test the software performance

B. To design the database schema

C. To write the program code

D. To show users and their interactions with system functions

Solution

1. Step 1: Understand the role of use case diagrams

   Use case diagrams visually represent how users (actors) interact with the system's functions (use cases).

2. Step 2: Compare with other software tasks

   Designing databases, coding, and testing are different activities not shown by use case diagrams.

3. Final Answer:

   To show users and their interactions with system functions -> Option D

4. Quick Check:

   Use case diagrams = show actors and interactions [OK]

Hint: Use case diagrams focus on users and their actions [OK]

Common Mistakes:

• Confusing use case diagrams with database design
• Thinking use case diagrams show code details
• Assuming use case diagrams test software

2. Which of the following is the correct symbol for an actor in a use case diagram?

easy

A. A stick figure

B. A rectangle

C. An oval

D. A diamond

Solution

1. Step 1: Identify actor symbol in use case diagrams

   Actors are represented by stick figures to symbolize users or external systems.

2. Step 2: Recognize other symbols

   Ovals represent use cases, rectangles and diamonds are not used for actors.

3. Final Answer:

   A stick figure -> Option A

4. Quick Check:

   Actor symbol = stick figure [OK]

Hint: Actors are stick figures in use case diagrams [OK]

Common Mistakes:

• Confusing actors with use cases (ovals)
• Choosing rectangles or diamonds for actors
• Not recognizing standard UML symbols

3. Consider a use case diagram with an actor "Customer" connected to two use cases: "Place Order" and "Track Order". What does this connection represent?

medium

A. Customer is a system component

B. Customer can perform both placing and tracking orders

C. Use cases depend on each other

D. Customer is a database entity

Solution

1. Step 1: Understand actor-use case connections

   Lines between an actor and use cases show the actor can perform those actions.

2. Step 2: Interpret the given connections

   Customer connected to "Place Order" and "Track Order" means the customer can do both activities.

3. Final Answer:

   Customer can perform both placing and tracking orders -> Option B

4. Quick Check:

   Actor connected to use cases = actor performs those actions [OK]

Hint: Lines show actor's possible actions [OK]

Common Mistakes:

• Thinking actors are system parts
• Assuming use cases depend on each other
• Confusing actors with database entities

4. A use case diagram shows an actor connected to a use case with a dashed arrow labeled "<<include>>". What is the likely issue if the arrow is drawn as a solid line instead?

medium

A. The diagram incorrectly shows a direct association instead of an include relationship

B. The actor symbol is wrong

C. The use case should be a rectangle

D. The diagram is missing actors

Solution

1. Step 1: Understand <<include>> notation

   The <<include>> relationship is shown with a dashed arrow from one use case to another, not from actor to use case.

2. Step 2: Identify the error in arrow style

   A solid line from actor to use case shows direct association, not an include relationship, so the diagram is incorrect.

3. Final Answer:

   The diagram incorrectly shows a direct association instead of an include relationship -> Option A

4. Quick Check:

   Include = dashed arrow between use cases, not solid actor line [OK]

Hint: <<include>> uses dashed arrows between use cases only [OK]

Common Mistakes:

• Drawing solid lines for <<include>>
• Confusing actor symbols with use case symbols
• Misplacing <<include>> arrows from actors

5. You want to model a system where a "User" can either "Login" or "Register" before accessing "Dashboard". Which use case diagram structure correctly shows that "Dashboard" use case requires either "Login" or "Register" first?

hard

A. "Login" and "Register" use cases extend "Dashboard" use case

B. "Dashboard" use case extends "Login" and "Register" use cases

C. "Dashboard" use case includes both "Login" and "Register" use cases

D. Login" and "Register" use cases are actors

Solution

1. Step 1: Understand include vs extend relationships

   Include means mandatory sub-function; extend means optional or conditional addition.

2. Step 2: Model login/register before dashboard

   Since "Dashboard" requires either "Login" or "Register" first, "Dashboard" use case includes both "Login" and "Register" use cases to show mandatory preconditions.

3. Final Answer:

   "Dashboard" use case includes both "Login" and "Register" use cases -> Option C

4. Quick Check:

   Include = mandatory use case inclusion [OK]

Hint: Use include for mandatory preconditions before main use case [OK]

Common Mistakes:

• Using extend instead of include for mandatory steps
• Confusing actors with use cases
• Reversing direction of include/extend arrows