UML Diagrams MCQs Questions With Answers – Part 10

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 UML class diagram, what does “1..*” mean?

A The element is optional

B It can be null or unique

C There is exactly one instance

D There is at least one instance

The multiplicity 1..* means there must be at least one instance (but potentially more). Unlike 0..*, which allows zero.

2. What does the notation ~ before a method in a class diagram mean?

A Private

B Package (default)

C Abstract method

D Protected

~: package (accessible only within the same package). Example:

The ~ symbol in UML is used to define a package visibility, meaning the element is only accessible within the package, not outside.

3. What is the main difference between a class diagram and an object diagram?

A The class diagram shows the actual execution

B The class diagram shows the abstract structure; the object diagram shows real instances

C The object diagram only shows methods

D The object diagram is used only for databases

Class diagrams show the general structure of the system, while object diagrams show the concrete objects and their relationships at a specific point in time.

4. What type of diagram is this model?

A Sequence diagram

B Use case diagram

C Activity diagram

D State diagram

This diagram represents the flow of actions, step by step, to order a product.

5. What does a stereotyped rectangle <<boundary>> represent in UML architecture?

A A hardware component

B A persistence class

C A design error

D An interface between the system and an external actor

The stereotype <<boundary>> represents a boundary class, often a user interface or an entry/exit point between the system and the outside (e.g., screen, API…). Example:

6. What error does this UML diagram contain?

A Missing attributes

B Incorrect notation for a method

C The class names are incorrect

D Nothing unusual

+speedUP : void should be written as +speedUP() : void, as in UML, a method must include parentheses even if it has no parameters.

7. What is the correct definition of a “secondary actor” in a use case diagram?

A The one who directly triggers a use case

B The one who is involved indirectly or in support

C The one who validates the results

D The one who connects to the interface

The secondary actor is not the primary initiator but participates in the use case (e.g., a payment system called by a user). Example:

The primary actor is a Customer who orders a product. The payment system is a secondary actor: it participates, but does not directly trigger the use case.

8. What is the purpose of a timing diagram in UML?

A To show the life cycles of objects

B To visualize the evolution of states over time

C To define user use cases

D To organize physical components

A timing diagram is a type of behavioral diagram used to show changes in an object’s state over time, often in a real-time context.

9. In a class diagram, which element contains attributes and operations?

A Object

B Class

C Use case

D Actor

A class contains attributes (data) and operations (methods) that define its behavior. Example:

10. What is the main difference between a class diagram and a component diagram?

A The class diagram shows the internal architecture of a system, while the component diagram shows its hardware deployment

B The class diagram describes the actions of the system, while the component diagram shows external actors

C The component diagram does not contain classes

D The class diagram is always more complex than a component diagram

A class diagram focuses on the internal structure (attributes and methods), while a component diagram shows how software components are deployed onto hardware.

1. In a UML class diagram, what does “1..*” mean?

2. What does the notation ~ before a method in a class diagram mean?

3. What is the main difference between a class diagram and an object diagram?

4. What type of diagram is this model?

5. What does a stereotyped rectangle <<boundary>> represent in UML architecture?

6. What error does this UML diagram contain?

7. What is the correct definition of a “secondary actor” in a use case diagram?

8. What is the purpose of a timing diagram in UML?

9. In a class diagram, which element contains attributes and operations?

10. What is the main difference between a class diagram and a component diagram?

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