UML Baiscs

Question 1

What is the basic premise of the UML

Answer 1

A software system can be modeled as a collection of collaborating objects

Question 2

Why do we build models

Answer 2

Models succinctly describe reality, show essencial details and filter out non-essential details

This allows us to focus in the big picture

Such focus allows us to deal with the complexity of software development

The result is a better understanding of the requirements, cleaner designs, and more maintainable systems

Question 3

What are class attributes?

Answer 3

An attribute describes the data values held by objects in a class

Question 4

What are the properties that can and have to be specified when creating classes attributes

Answer 4

Name of the attribute, its type and its visibility are required. We can than define its initial value, multiplicity and its changeability

Question 5

How can we define the visibility of a class attribute?

Answer 5

Public (+)

Private (-)

Protected (#)

Package (~)

Question 6

What are class operations

Answer 6

They describes a function or transformation that may be applied to or by objects in a class

Question 7

How do we specify operations in a class?

Answer 7

Name, parameters, the result type and its visibility

Question 8

How do we call an operation instance? What about when an operation have several methods that implement it?

Answer 8

The implementation of an operation is called a method

And when there are more than one method the implements an operation we call it polimorphic operation

Question 9

What are links and associations and how do they relate to each other?

Answer 9

Links are relationships between objects

Associations are a description of the links between objects

Question 10

What are the possible interpretations of associations?

Answer 10

Conceptually, associations are bi-directional

You can show navegability of associations with an arrowhead (implies that’s the source object has a reference to the target object)

Question 11

What are the multiplicities in associations?

Answer 11

They specify a restriction on the number of objects in a class that may be related to an object in other class

Question 12

Why is the obvious way for storing data in a UML class diagram?

Answer 12

The obvious option in to store as an attribute under the classes

Question 13

What is the second option for storing data in a UML class diagram?

Answer 13

The second option is to use a multi-valued attribute for the data, where we have an array of grades under the student.

Question 14

What is the limitation of using a multi-valued attribute for the data?

Answer 14

We might have a problem of data correspondence

Question 15

What is the third option for storing data in a UML class diagram?

Answer 15

The third option is to use an association class to model the properties of the association between the two associated classes.

Question 16

How does the association class help in storing grades?

Answer 16

The association class allows us to store the data under the association between the classes

Question 17

What is the limitation of using an association class for storing data?

Answer 17

The limitation is that if there are more than one link between the objects, we can only keep track of the most recent one, losing the historical information.

Question 18

What is generalization in software engineering

Answer 18

Is a relationship between classes of the same kind, where a class can be specialized into different subclasses

Question 19

How can generalization be represented in a class diagram

Answer 19

Using a triangle symbol

Question 20

What are the two approaches to performing generalization?

Answer 20

The two approaches are top-down and bottom-up. In top-down, we start with a general class and specialize it into specific subclasses. In bottom-up, we identify similar classes and generalize them into a more general class.

Question 21

What is the benefit of using inheritance in generalization?

Answer 21

Inheritance allows us to extract common attributes, relationships, and operations and put them in a superclass. This promotes reusability and simplifies modification of descriptions.

Question 22

What is overriding in inheritance?

Answer 22

Overriding is when a subclass defines its own version of an operation that is already defined in the superclass. The subclass’s version of the operation will be used instead of the superclass’s version when applicable.

Question 23

What are overlapping and disjoint coverage in generalization?

Answer 23

Overlapping coverage means that some instances can belong to multiple subclasses. Disjoint coverage means that instances can only belong to one subclass and not to multiple subclasses.

Question 24

What is completeness coverage in generalization?

Answer 24

Completeness coverage refers to whether all possible instances are covered by the subclasses. It can be either complete, meaning all instances are covered, or incomplete, meaning there may be instances not covered by the subclasses.

Question 25

How can additional information be provided in a class diagram?

Answer 25

Additional information can be provided using notes in the class diagram. For example, if there are specific constraints or details about the subclasses, they can be mentioned in a note beside the diagram.

Question 26

What is UML and how is it used in software engineering?

Answer 26

- UML stands for Unified Modeling Language and it is a standardized visual language used to model software systems. - It helps software engineers to visualize, specify, construct, and document the artifacts of a software system.

Question 27

What are the different types of relationships in class diagrams?

Answer 27

- The different types of relationships in class diagrams are aggregation, composition, and generalization. - Aggregation represents a "has-a" relationship between classes. - Composition is a stronger form of aggregation where the lifetime of the contained class is dependent on the container class. - Generalization represents an "is-a" relationship where one class is a specialized version of another class.

Question 28

How can additional constraints be specified in UML diagrams?

Answer 28

- Additional constraints can be specified in UML diagrams to define certain requirements or conditions. - Constraints can be added alongside operations or as notes in the class diagram. - They are statements that can be tested to be true or false, and they help enforce specific rules or conditions in the system.

Question 29

What is system requirements capture and domain modeling?

Answer 29

- System requirements capture involves identifying and documenting the requirements of a software system. - Domain modeling is the process of capturing the entities and relationships within a specific application domain using class diagrams.

Question 30

What is UML?

Answer 30

UML stands for Unified Modeling Language. It is a general-purpose visual modeling language used to represent systems.

Question 31

Is UML specific to object-oriented systems?

Answer 31

While UML is suitable for object-oriented systems, it can also be used for non-object-oriented systems.

Question 32

What are the building blocks of UML?

Answer 32

The building blocks of UML include important objects, relationships, and diagrams that are used to represent a system.

Question 33

What are the different perspectives in UML?

Answer 33

UML allows us to build models from different perspectives, such as the use-case view, logical view, implementation view, process view, or deployment view

Question 34

What is the class diagram used for?

Answer 34

The class diagram is used to capture the data requirements within a software system. It represents a collection of objects and their relationships.

Question 35

Why do we build models in software development?

Answer 35

Models are built to facilitate effective communication among stakeholders and to focus on the big picture of the software system. They help us understand requirements, design, and create more maintainable software systems.

Question 36

What are the benefits of building models?

Answer 36

Building models helps ensure consistent understanding among stakeholders, allows us to focus on the big picture, and helps us deal with the complexity of software development.

Question 37

How does the class diagram help in capturing data requirements?

Answer 37

The class diagram allows us to identify and represent the important objects within the application domain, such as organizations, people, and cars. It helps us capture the relationships between these objects and their attributes, which are essential for understanding the data requirements of the software system.

Question 38

What are the different types of UML diagrams?

Answer 38

The different types of UML diagrams include class diagrams, use case diagrams, sequence diagrams, activity diagrams, and more.

Question 39

What are the types of relationships that can be represented in a class diagram?

Answer 39

The types of relationships in a class diagram include association, aggregation, composition, and inheritance.

Question 40

What is domain modeling?

Answer 40

Domain modeling is the process of creating a conceptual model that represents the entities, attributes, and relationships within a specific problem domain.

Question 41

What are associations in class diagrams?

Answer 41

Associations in class diagrams represent links between objects or classes within a system.

Question 42

What are the three types of associations in class diagrams?

Answer 42

The three types of associations are unary, binary, and ternary associations.

Question 43

Can you explain unary associations?

Answer 43

Unary associations involve instances within the same class associating with each other.

Question 44

What is the concept of bidirectional associations?

Answer 44

Bidirectional associations mean that associations are associated with each other, allowing for connections between objects in both directions.

Question 45

How can navigability be represented in associations?

Answer 45

Navigability can be represented using arrowheads to indicate dependencies between classes.

Question 46

Can there be multiple associations between the same pair of classes?

Answer 46

Yes, as long as the associations have different meanings, multiple associations can exist between the same pair of classes.

Question 47

What are multiplicities in class diagrams?

Answer 47

Multiplicities specify the number of objects that can be related to each other in an association.

Question 48

How are multiplicities represented in class diagrams?

Answer 48

Multiplicities are represented using lower and upper bounds to define the range of associations.

Question 49

How are multiplicities represented in class diagrams?

Answer 49

Multiplicities are represented using lower and upper bounds to define the range of associations.

Question 50

What is the difference between aggregation and composition?

Answer 50

- Aggregation and composition represent the "part of" relationship between classes. - Aggregation indicates optional participation, while composition indicates mandatory participation.

Question 51

How do you decide whether to use aggregation or composition?

Answer 51

- The decision to use aggregation or composition depends on whether the part is dependent on the whole. - If destroying the whole also destroys the part, composition should be used. - If the part can exist independently of the whole, aggregation should be used.

Question 52

What is the primary purpose of a class diagram in software development?

Answer 52

The primary purpose of a class diagram is to model a system by representing its components as classes. This helps in understanding the system's important components, facilitating system specification, and promoting modularity in software development.

Question 53

What is a class, and how is it used in a class diagram?

Answer 53

A class is a blueprint for grouping objects that share common attributes and operations. In a class diagram, classes are used to represent the major components of a system. For example, in a banking software system, different types of bank accounts can be represented as a single class called "account."

Question 54

Why is it important to capture only one abstraction in a class?

Answer 54

Capturing only one abstraction in a class ensures clarity and precision. A class should represent one important concept within the application domain and should be named using meaningful, domain-specific vocabulary that is traceable.

Question 55

What are attributes in the context of a class, and why are they important?

Answer 55

Attributes are properties or characteristics of a class. They are important because they define the data associated with objects of the class. For instance, in the "account" class, attributes might include account number and balance.

Question 56

What are operations in a class diagram, and what role do they play?

Answer 56

Operations are functions or transformations that can be applied to objects within a class. They define the behavior of the class. For example, operations for an "account" class might include checking the balance, depositing money, and withdrawing money.

Question 57

What is the difference between an operation and a method in a class?

Answer 57

An operation describes a function or transformation that can be applied to objects of a class, while a method is the specific implementation of that operation. Multiple methods can implement the same operation in different ways.

Question 58

What are the benefits of using classes to model software systems?

Answer 58

Using classes to model software systems helps in understanding the system's important components, facilitates system specification, and promotes modularity. Representing the system as a collection of objects and classes also aids in clear and structured design

Question 59

Why is choosing the appropriate classes considered an important design decision?

Answer 59

Choosing appropriate classes is crucial because it directly impacts the modularity and structure of the software. Proper class selection leads to a more organized and maintainable system design.