UML Diagrams MCQs Questions With Answers – Part 12

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. What is the difference between a sequence diagram and a communication diagram?

A The sequence diagram shows interactions over time, while the communication diagram shows the objects and their relationships.

B The communication diagram shows the order of messages, while the sequence diagram shows only the objects.

C The sequence diagram does not show the messages sent between objects.

D Both diagrams are identical.

A sequence diagram shows the order of messages between objects, while a communication diagram emphasizes the relationships between objects, but does not follow the order of messages.

2. What is the nature of the relationship between Customer and Order?

A Inheritance

B Strong association

C Dependency (usage)

D Composition

The dashed line ..> indicates that Customer depends on Order, for example, via a parameter or a temporary method. This is not a persistent structural relationship.

3. What is the role of a “use case” in a use case diagram?

A It defines a service provided by the system to the actor.

B It represents a type of relationship between classes.

C It is used to model the messages between objects.

D It shows the structure of the database.

A use case represents a specific service or functionality that the system provides to an actor, responding to a need or request from the user.

4. What is the problem in this diagram?

A A missing arrow between the classes

B There is no constructor

C The method `viewItems()` has no visibility

D The type List is invalid in UML

In UML, each attribute and method must have visibility (+ public, – private, # protected). Here, the `+` is missing before `viewItems`.

5. What is “multiplicity” in a class diagram?

A The number of methods in a class

B The number of instances of a class that can be linked to another class

C The depth of inheritance of a class

D The type of relationship between two classes

Multiplicity defines how many instances of a class can be associated with an instance of another class. Example: 1..* means one or more instances.

6. In a sequence diagram, what does a lifeline with a vertical bar signify?

A The object is deleted

B The object is waiting for a response

C The object is active during message sending

D The object enters a waiting state

A vertical bar on a lifeline in a sequence diagram indicates that an object is active (sending or receiving messages). This shows that the object is being processed at that moment.

7. In a communication diagram, how are relationships between objects represented?

A By curved arrows between objects

B By dashed lines

C By rectangles with links inside

D By simple arrows connecting the objects

In a communication diagram, objects are connected by simple arrows indicating the exchanged messages. This shows the relationships and communication between objects. Example:

8. In a use case diagram, what type of relationship is used to link a use case to an actor?

A Inclusion

B Extension

C Association

D Generalization

In a use case diagram, an association links an actor to a use case. This relationship shows that the actor interacts with the use case by triggering an action. Example:

9. In UML, what is a “package”?

A An independent diagram

B A special method

C A logical grouping of classes

D A database

A package is used to organize UML elements (classes, interfaces…) into logical groups.

10. What type of UML relationship uses a simple arrow without a diamond?

A Composition

B Aggregation

C Association

D Deployment

In a use case diagram, an association links an actor to a use case. This relationship shows that the actor interacts with the use case by triggering an action.

1. What is the difference between a sequence diagram and a communication diagram?

2. What is the nature of the relationship between Customer and Order?

3. What is the role of a “use case” in a use case diagram?

4. What is the problem in this diagram?

5. What is “multiplicity” in a class diagram?

6. In a sequence diagram, what does a lifeline with a vertical bar signify?

7. In a communication diagram, how are relationships between objects represented?

8. In a use case diagram, what type of relationship is used to link a use case to an actor?

9. In UML, what is a “package”?

10. What type of UML relationship uses a simple arrow without a diamond?

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