UML Diagrams MCQs Questions With Answers – Part 22

April 20, 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 UML class diagram, what does a simple arrow on an association between two classes indicate?

A A unidirectional dependency.

B Possible navigation in both directions.

C Unidirectional navigability, from the source class to the target class.

D An abstract relationship with no possible interaction.

An arrow on an association indicates that the source class is aware of the target class, but not vice versa. Without an arrow, the association is bidirectional. Example:

2. What does this diagram represent?

A It shows the classes and their dependencies

B It illustrates different user interfaces

C It models the life cycle of a document

D It represents a database process

It’s a state diagram, showing the successive states of an object (Draft → Published → Archived) with triggering events (publish, archive).

3. You’re creating a streaming app. Which diagram would help model the scenario “the user starts a video”?

A Sequence diagram

B State diagram

C Use case diagram

D Component diagram

A Use Case Diagram is best used when:

You’re identifying high-level user interactions with the system.
You want to model “what” a user can do, not “how” it happens step-by-step.

So in the case of: “The user starts a video”
✅ That’s a use case — a goal the user wants to achieve with the system.

4. In a quiz app, a player answers several questions. What is the relationship between the two?

A Dependency

B Aggregation

C Composition

D Association

The player is linked to the questions, but they can exist without the player → simple association.

5. What is the default visibility of a UML element contained in a package?

A + (public)

B – (private)

C # (protected)

D ~ (package)

The ~ visibility means package visibility, i.e., the element is only accessible to elements within the same package. It is neither fully public nor private, useful for modular encapsulation. Example:

6. In a class diagram, what does an underlined attribute (e.g.: id: int) mean?

A It is a private attribute

B It is a static attribute

C It is an inherited attribute

D It is a constant

In UML, an underlined attribute indicates it is static (shared by all instances).

7. What is the purpose of a UML profile?

A Customize UML with stereotypes, constraints, and tags specific to a domain.

B Change the UML syntax into a new language.

C Add custom classes to a UML library.

D Transform a UML diagram into executable code.

A UML profile is a standard mechanism for adapting UML to specific needs (like UML for embedded systems, systems engineering, etc.). It includes stereotypes (<<>>), tagged values, OCL constraints, etc.

8. You’re modeling a transport app. A trip is linked to a driver and a car. Which diagram best shows everything?

A Sequence diagram

B Class diagram

C Activity diagram

D State diagram

The class diagram models the links between structured entities, like in this case. Example:

9. In a state diagram, what triggers a transition from one state to another?

A A class change

B A message or event

C A boolean variable

D An external package

A transition between states is triggered by an event (e.g., user click, signal received, timeout end, etc.). Transitions can have guards (conditions) and actions.

10. In a UML communication diagram, what does a link between two objects represent?

A A static relationship between two classes

B A physical link between two components

C An instance of an association between two objects

D A state transition

In a communication diagram, a link shows that two objects can exchange messages. It represents an instance of an association. Messages are numbered to indicate their order. Example:

Objects are represented as in an object diagram. Arrows show messages exchanged between them. The numbering (1, 1.1, 1.2) indicates the order of interactions in the scenario.
Here, a client orders a product:

The Client sends a request to an OrderService
The OrderService checks with a Stock
Then it confirms the order

1. In a UML class diagram, what does a simple arrow on an association between two classes indicate?

2. What does this diagram represent?

3. You’re creating a streaming app. Which diagram would help model the scenario “the user starts a video”?

4. In a quiz app, a player answers several questions. What is the relationship between the two?

5. What is the default visibility of a UML element contained in a package?

6. In a class diagram, what does an underlined attribute (e.g.: id: int) mean?

7. What is the purpose of a UML profile?

8. You’re modeling a transport app. A trip is linked to a driver and a car. Which diagram best shows everything?

9. In a state diagram, what triggers a transition from one state to another?

10. In a UML communication diagram, what does a link between two objects represent?

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