UML Diagrams MCQs Questions With Answers – Part 6

April 19, 2025 John Howard

Test your knowledge and boost your confidence with these multiple-choice quizzes focused on UML diagrams, foundational software engineering concepts, and real-world best practices. Designed for students, developers, and exam candidates, these MCQs offer a quick and effective way to assess your understanding and sharpen your skills.

1. In a class diagram, what does a solid triangular-headed arrow pointing towards an interface represent?

A Association

B Dependency

C Realization (implementation)

D Generalization (inheritance)

The realization relationship indicates that a class implements an interface and must therefore provide an implementation for all the operations defined in this interface. Example:

A Flying interface defines a method fly(). A Plane class implements this interface, so it must provide the implementation of fly().

2. In a sequence diagram, what does a solid line arrow with an open head represent?

A A creation message

B A synchronous message

C An asynchronous message

D A response

A synchronous message (regular method call) is represented by a solid arrow with an open head. This means the sender waits for a response before continuing. Example:

The diagram shows a classic scenario: A client sends a request, the server processes it, then returns a response. Since the call is synchronous, the client waits for the processing to finish before proceeding.

3. Which UML diagram is most useful for understanding the end-user perspective?

A Class diagram

B Activity diagram

C Use case diagram

D Component diagram

The use case diagram is focused on what the user wants to do with the system. It’s ideal for discussing with clients and analyzing functional needs.

4. What does a solid arrow with a white triangular head mean in a class diagram?

A An association

B An aggregation

C A composition

D A generalization (inheritance)

Generalization, which represents an inheritance relationship, is drawn with a solid arrow and a white triangle pointing to the superclass. Example:

5. What does the # symbol before a method mean?

A Public method

B Private method

C Protected method

D Abstract method

# : protected (accessible only within the class and its subclasses)

6. In an activity diagram, what does a diamond represent?

A A condition or test (decision)

B An end of process

C A start of process

D A system error

In an activity diagram, a diamond represents a decision (like an if), with multiple outgoing arrows that are conditioned. Example of an online order process:

7. In UML, what do we call an event that triggers a transition in a state diagram?

A A stimulus

B An action

C A signal

D A trigger

A trigger is an event that causes a state change of an object in a state diagram. Example:

An event (like paying or canceling) in a UML state diagram is what triggers a transition from one state to another.

8. What does an activity diagram represent?

A Inheritance between classes

B Business process or workflow

C The database

D Relationships between actors

It describes the flow of a process in terms of activities and decisions (like conditional instructions).

9. What does the following UML diagram represent?

A It shows the states of a bank account

B It describes the interactions between the client and the account

C It defines the structure of a class called BankAccount

D It represents a transaction process

This is a class diagram describing the attributes and methods of a class called BankAccount.

10. Which UML diagram focuses on the organization of objects and their links at a specific moment in time?

A Class diagram

B Sequence diagram

C State-transition diagram

D Object diagram

An object diagram is a specific instance of a class diagram. It shows a set of objects and their relationships at a precise moment, providing a snapshot of the system’s structure during execution.