UML Diagrams MCQs Questions With Answers – Part 15

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. A composition differs from an aggregation by:

A The direction of the arrow

B The style of the diamond

C The multiplicity

D The names of the classes

Aggregation: white diamond (weak relationship)
Composition: black diamond (strong relationship, dependent existence)

Example:

2. What is missing in this diagram?

A There is no associated class

B getPrice is incorrectly defined

C The attributes are not typed

D The constructor is missing

In UML, a method must have parentheses. Therefore, getPrice should be: +getPrice() : double.

3. In a sequence diagram, what is the purpose of a return message (dashed line with a solid arrow)?

A To illustrate a dependency

B To represent a state transition

C To complete a diagram

D To show a response to a method call

A dashed line with an arrow in a sequence diagram represents a return message: it is the response to a method call.

4. In a sequence diagram, what symbol is used to send a synchronous message?

A Dashed line

B Solid arrow with a black triangle head

C Solid arrow with an open head

D Empty arrow

A synchronous message is represented by a solid arrow with a black triangle head, indicating that a response is expected. Example:

5. In UML, what do we call a class that cannot be instantiated directly?

A A utility class

B A concrete class

C An abstract class

D An external class

An abstract class is a class that cannot be instantiated directly. It is often used as a base for other concrete classes. In UML, it is denoted in italics or marked with the <<abstract>> stereotype.

6. What is the issue in this diagram?

A The class names are too short

B There is unhandled recursion

C Methods are missing

D The “inheritance” relationship is poorly represented

Inheritance should be represented by a triangular arrow (A <|-- B), not a simple arrow -->. Example:

7. What is the main difference between a dependency and an association in UML?

A An association is temporary, a dependency is permanent

B A dependency is stronger than an association

C An association involves a direct link between objects, a dependency does not

D There is no significant difference

An association represents a permanent structural link between classes (e.g., a student and their class). A dependency is weaker: it indicates that a class temporarily uses another without a direct link. Example:

8. In UML, what does a generalization arrow between two use cases mean?

A A process inclusion

B An inheritance between actors

C A functional dependency

D A specialization of a use case

A generalization arrow between two use cases indicates that the child use case specializes or extends the behavior of the parent use case. This allows modeling variations. Example:

Parent use case: Order a product
Child use case: Order with express shipping, which specializes the parent behavior (e.g., fast delivery)

9. In a class diagram, what is an operation?

A A relationship between two classes

B A calculated attribute

C A method that a class can execute

D An abstract class

An operation is equivalent to a method in UML: it represents a function that the class can perform. For example: display(), calculateTotal(), etc.

10. What does this diagram represent?

A A hierarchy of inheritance between concrete classes

B An abstract class with two subclasses

C A class that implements two interfaces

D Two classes merged into one

The notation ..|> means that the class MultifunctionPrinter implements both the Printable and Scannable interfaces.

1. A composition differs from an aggregation by:

2. What is missing in this diagram?

3. In a sequence diagram, what is the purpose of a return message (dashed line with a solid arrow)?

4. In a sequence diagram, what symbol is used to send a synchronous message?

5. In UML, what do we call a class that cannot be instantiated directly?

6. What is the issue in this diagram?

7. What is the main difference between a dependency and an association in UML?

8. In UML, what does a generalization arrow between two use cases mean?

9. In a class diagram, what is an operation?

10. What does this diagram represent?

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