Lecture 10 - GRASP

Question 1

What is the focus of object design?

Answer 1

Identify classes and objects, decide what methods belong were, and how these objects should interact

Question 2

What are responsibilities regarding objects?

Answer 2

Obligation of an object in terms of behaviour

Question 3

What are the two types of responsibilities regarding objects?

Answer 3

• Doing
• Knowing

Question 4

What does the Doing responsibility do regarding objects? (3)

Answer 4

• Doing something (i.e. creating object, doing calculation)
• Initiating action in other objects
• Controlling + coordinating activities in other objects

Question 5

What does Knowing responsibility do regarding objects? (3)

Answer 5

• Knowing about private encapsulated data
• Knowing about related objects
• Knowing about things it can derive or calculate

Question 6

When are responsibilities assigned to classes?

Answer 6

During object design

Question 7

“A sale is responsible for creating a SalesLineItems” is an example of…

Answer 7

the Doing responsibility

Question 8

“A sale is responsible for knowing its total” is an example of…

Answer 8

the Knowing responsibility

Question 9

TF: Responsibilities related to “Knowing” are often inferable from the Domain Model

Answer 9

True. Because of attributes and associations illustrated in it

Question 10

The translation of responsibilities into classes and methods is influenced by what?

Answer 10

Granularity of responsibility

Question 11

TF: Responsibility is the same thing as a method

Answer 11

False. Methods are implemented to fulfill responsibilities, but they are not the same thing

Question 12

Within UML artifacts, what is a common context in which responsibilities are considered?

Answer 12

During the creating of Interaction Diagrams

Question 13

What do Patterns guide?

Answer 13

Guide choices in where to assign responsibilities

Question 14

What is a named description of a problem and a solution that can be applied to new contexts?

Answer 14

Patterns

Question 15

TF: A pattern provides advice in how to apply a solution to a problem in varying circumstances

Answer 15

True

Question 16

What is the basic idea of Information Expert?

Answer 16

To assign a responsibility to the object (class) that has the most information necessary to fulfill it

Question 17

Fulfillment of a responsibility often requires information spread across different classes, what can the other classes be known as?

Answer 17

Partial experts

Question 18

The class responsible for creating instances of another class is called a…

Answer 18

Creator

Question 19

What conditions does a class ‘A’ need to satisfy to be considered a Creator for class ‘B’? (4)

Answer 19

• A aggregates B objects
• A contains B objects
• A records instances of B objects
• A has the initializing data that will be passed when B is created

Question 20

What is the problem with Solution by Expert?

Answer 20

Can sacrifice high cohesion and low coupling

Question 21

What is a design pattern that doesn’t sacrifice high cohesion and low coupling?

Answer 21

Pure fabrication

Question 22

What is pure fabrication pattern?

Answer 22

A pattern in which a separate class that doesn’t represent a domain concept is created to handle a responsibility

Question 23

How can you enforce low coupling?

Answer 23

By assigning a responsibility to ensure coupling stays low

Question 24

What are the places where coupling occurs? (4)

Answer 24

• Attributes: X has attribute that refers to Y
• Methods: parameters/local variables of type Y found in method of X
• Subclasses: X subclass of Y
• Types: X implements interface Y

Question 25

What is Protected variation pattern?

Answer 25

Pattern aimed to reduce variation/instability in one element from having undesirable effects on other elements

Question 26

What is a way to incorporate Protected variation?

Answer 26

By encapsulating elements that could vary (using interfaces or abstract classes)

Question 27

TF: A benefit of Protected variation is it makes the system easier to maintain and understand

Answer 27

True

Question 28

What is Open-closed pattern?

Answer 28

Pattern where classes, modules, functions should be open for extension but closed for modification

Question 29

How do you apply the Open-closed pattern?

Answer 29

By identifying points of predicted changes/extension within components and create stable interfaces or extension points

Question 30

Extensibility of individual software components (easy extension without modifying existing code) is the goal of what pattern?

Answer 30

Open-closed pattern

Question 31

Managing dependencies between components to protect against changes in other components (using abstraction/interfaces to minimize direct dependencies) is the goal of what pattern?

Answer 31

Protected variation pattern

Question 32

What is the similarity between Open-closed pattern and Protected variation pattern?

Answer 32

Use of interfaces/abstraction to protect components from changes or variation

Question 33

What are the problems with low cohesion? (4)

Answer 33

- Hard to understand - Hard to reuse - Hard to maintain - Easily affected by change

Question 34

How to enforce high cohesion?

Answer 34

Assign a responsibility so cohesion remains high

Question 35

A class responsible for interfacing with a data based on remote-procedure calls is an example of what type of cohesion?

Answer 35

Very low cohesion

Question 36

A class responsible for interfacing with a relational database is an example of what type of cohesion?

Answer 36

Low cohesion

Question 37

Airline class that knows about personnel and finance is an example of what type of cohesion?

Answer 37

Moderate cohesion

Question 38

A class responsible for one section of interfacing with a database (i.e Sale object in a POS)?

Answer 38

Class/High cohesion

Question 39

TF: A class with high cohesion has a relatively low number of methods that are highly related

Answer 39

True

Question 40

TF: A class with high cohesion does a lot of work

Answer 40

False. It doesn't do much work and mostly collaborates and delegates

Question 41

What is the Controller Pattern?

Answer 41

Pattern in which responsibility for receiving or handling a system event message is assigned to a class

Question 42

The class selected as the Controller must represent what? (3)

Answer 42

One of the following: - Represents overall system - Represents a use case scenario - A Controller is a non-user interface object that defines methods for the system operation

Question 43

What is indirection?

Answer 43

Measure of how abstracted and managed the relationships and dependencies between software components are

Question 44

How can we manage relationships and dependencies between components effectively and maintainable?

Answer 44

Assign responsibilities for managing relationships and dependencies using abstraction layers (a.k.a indirection)

Question 45

When complex systems need to maintain flexibility and compatibility across various implementation, you should use...

Answer 45

an interface

Question 46

In scenarios where specific behaviours or attributes must be realized with precision and consistency, you should use...

Answer 46

a class

Question 47

Which design principle can help address concerns about the impact of changes in a system and promote well-organized code? a. Creator b. Information Expert c. High Cohesion d. All of the mentioned

Answer 47

c. High Cohesion

Question 48

In a system adhering to the Creator pattern in GRASP, how are responsibilities assigned for creating Payment and processing it between Sale and Register? a. Sale creates Payment, and Register serves as a Controller to facilitate payment processing. b. Sale creates Payment, and Register is not directly involved in payment processing. c. Register creates Payment, and Sale processes payments. d. None of the above.

Answer 48

a. Sale creates Payment, and Register serves as a Controller to facilitate payment processing.

Question 49

What is the primary advantage of using the Information Expert pattern for responsibility assignment in object-oriented design? a. It promotes high cohesion and low coupling between objects. b. It simplifies the structure of the system. c. It allows for more flexible and dynamic object interactions. d. It reduces the number of objects in the system, leading to improved performance

Answer 49

a. It promotes high cohesion and low coupling between objects.

Question 50

With regard to the creator pattern, we should assign class B the responsibility of creating an instance of class A if which of the following conditions are true? a. A records B b. B knows about A c. B closely uses A d. All of the above

Answer 50

b. B knows about A

Question 51

All are correct about pure fabrication pattern except: a. Achieve low coupling b. Achieve high cohesion c. Represent a concept in the problem domain d. Represent a concept in the solution domain

Answer 51

c. Represent a concept in the problem domain