chapter 6

Question 1

What is design methodology?

Answer 1

logical and systematic steps to progress the design process.

also a set of guidelines for decision making.

Question 2

What is refactoring (design methodology)?

Answer 2

Design decisions are revisited and revised.

Question 3

What are design principles? Name the 6 principles.

Answer 3

Characteristics of good design.
Guidelines for decomposing a system.

1. Modularity
2. Interfaces
3. Information hiding (public, protected, private)
4. Incremental development
5. Abstraction
6. Generality

Question 4

What is modularity in design principles?

Answer 4

A well organized system. Unrelated aspects are kept separate.

Each component has a single purpose.

Use coupling and cohesion to accomplish modularity.

Question 5

What is coupling in design principles?

Answer 5

Degree by which software components are dependent on each other. Low coupling is better.

Tightly coupled: depend greatly on each other.
Loosely coupled: some dependencies.
Uncoupled: no dependencies.

Question 6

What is content coupling?

Answer 6

Tightly coupled. A module that modifies the internal elements of another module. (internal access not public or protected methods).

Question 7

What is common coupling?

Answer 7

Data is duplicated and kept in different modules. A change to the data needs to be changed in all duplicated locations.

Question 8

What is control coupling?

Answer 8

When a module passes parameters or return code to control another module.

Question 9

What is data coupling?

Answer 9

Data coupling is where modules are connected by unstructured data.

Question 10

What is stamp coupling?

Answer 10

When two modules are connected by structured data (JSON format, csv, etc).

Question 11

What is cohesion? What are the 7 types of cohesion?

Answer 11

Degree to which the elements inside a module belong together. High cohesion is better (think MVC).

1. coincidental
2. logical
3. temporal
4. procedural
5. communicational
6. functional
7. informational

Question 12

What is coincidental cohesion?

Answer 12

A module containing unrelated elements; low cohesion.

Question 13

What is logical cohesion?

Answer 13

Parts are related only by the logic structure not functionally; low cohesion.

Question 14

What is temporal cohesion?

Answer 14

Elements of a component are related by timing.

Question 15

What is procedural cohesion?

Answer 15

Ensures the order of the execution; algorithms.

Question 16

What is communication cohesion?

Answer 16

Multiple modules operates on the same data set (input or output). Place each dataset in its own module.

Question 17

What is functional cohesion?

Answer 17

All elements essential to a function are contained in one module, and all of the elements are essential to the performance of the function.

The ideal solution.

Question 18

What is informational cohesion?

Answer 18

Adaptation of functional cohesion to data-abstraction and object-based design.

Parts of a module are grouped together as they are suppose to operate on the same data or information.

Question 19

What is an interface (design principle)?

Answer 19

defines the services of a system,
defines how units access the services; public methods.

A module can have several interfaces.

Question 20

What is the specification of a software unit’s interface?

Answer 20

A description of the externally visible properties of a software system.

1. purpose: description of the function.
2. preconditions: requirements of the function (variables, libraries, etc.).
3. protocols: sequence of function calls.
4. postconditions: return values, exceptions, modified variables.
5. quality attributes: no description given…

Question 21

What is information hiding?

Answer 21

Public, private, protected; only necessary information is shown. Good use of information hiding allows units to be loosely coupled.

Question 22

What is incremental development?

Answer 22

Software is developed in phases.

Dependencies are used to design a development schedule for scrum.

Question 23

What do “uses graphs” help a system do?

Answer 23

Helps to identify progressively larger subsets of our system that can be implemented and tested incrementally.

Fan-in: number of higher level modules that call this module.
Fan-out: number of lower level modules that this module uses.

Question 24

What is sandwiching in incremental development?

Answer 24

A technique to break cycles in the “use graph,” It involves decomposing one unit so that the cycle ends.

Question 25

What is abstraction (design principle)?

Answer 25

A general model that omits details. | Super class, sub class.

Question 26

What is generality (design principle)? How is it done?

Answer 26

Making software as universally applicable as possible to increase the chance it will be useful in some future system. Done by: 1. Parameterizing context-specific info. 2. Removing preconditions. 3. Simplifying postconditions.

Question 27

What is OO design?

Answer 27

A decomposition of a system into runtime components called objects that encapsulate data and functionality. 1. objects are uniquely "identifiable" runtime entities. 2. objects can be "composed"; object's variables can be objects themselves. 3. OO code can be polymorphic, generic code that works with objects of related types.

Question 28

What is a class (OO design)?

Answer 28

Software module that partially or fully implements an abstract data type. It is essentially a custom data type.

Question 29

What is an abstract class (OO design)?

Answer 29

A class with missing implementations for some of its methods.

Question 30

What is a constructor (OO design)?

Answer 30

A function that runs when a new instance of an object is created.

Question 31

What is an instance of a class (OO design)?

Answer 31

A specific example of a class.

Question 32

What are attributes in a class (OO design)?

Answer 32

object's data attributes.

Question 33

What are methods in a class (OO design)?

Answer 33

object's functions.

Question 34

What is dynamic binding (OO design)?

Answer 34

Method overloading. The compiler cannot determine the binding at compile time. When the program runs then the binding is determined.

Question 35

What is multiplicity (OO design)?

Answer 35

Used in diagrams. Represents the relationship between objects. (1 to many).

Question 36

What is object composition (OO design)?

Answer 36

New classes built by combining component classes.

Question 37

What is inheritance (OO design)?

Answer 37

Creating a new class by extending an existing one.

Question 38

What is polymorphism (OO design)?

Answer 38

Code that interacts with an interface. | The actual bindings are figured out during run-time.

Question 39

What are the two techniques for constructing large objects (OO design)?

Answer 39

inheritance: subclass's implementation is determined at design time. composition: better to preserve encapsulation and code reuse.

Question 40

What is the Law of Demeter (OO design)?

Answer 40

Communicate to immediate closest friends. A -> B -> C If A wanted to execute a method in C, it should tell B to do it.

Question 41

What is dependency inversion principle (OO design)?

Answer 41

High level code must not depend on low level code. Store -> Payment Class -> Paypal API, Visa API Store just needs to run a pay event. It doesn't need to know how to do it.

Question 42

Define the types of relationships in an ER-diagram. (6 types)

Answer 42

association: relationship. A married to B. (straight line) composition: cannot exist on its own. a person has a heart. (closed diamond) aggregation: can exist on its own. a company has employees. (open diamond) generalization (inheritance): sub class -> super class (open triangle) dependency: one module depends on another (dashed arrow) navigation: can access another without them knowing? (solid arrow)

Question 43

What is class description template?

Answer 43

A template that looks like python code.

Question 44

What is a package diagram?

Answer 44

Shows the system as a collection of packages and their dependencies. Each package can contain many classes. Useful for testing.

Question 45

What is a sequence diagram?

Answer 45

A diagram that shows a sequence of activities or behaviors.

Question 46

What is a communication diagram?

Answer 46

A sequence of messages between objects.

Question 47

What is a state diagram?

Answer 47

The possible states an object can take and the events that trigger transitions.

Question 48

What is an activity diagram?

Answer 48

Flow of procedures or activities in a class.

Question 49

Define OO design patterns?

Answer 49

A template of a solution based on design principles. It is not a library, rather a concept. MVC.

Question 50

What is template model pattern (design patterns)?

Answer 50

``` The use of inheritance to create sub-classes. The abstract class implements common steps. The sub-classes implement specific steps. ```

Question 51

What is the factory method pattern?

Answer 51

Encapsulates code that creates objects. Useful for creating a class at run-time (subclass type cannot be determined at compile time). EnemyShip -> UFO or ROCKET.

Question 52

What is the strategy pattern?

Answer 52

Allows algorithms to be selected at runtime. Animals (super class), Dog + Bird (sub classes). Algorithm = fly();

Question 53

What is the decorator pattern?

Answer 53

Extends an object's functionality at runtime. Adding more toppings to a pizza at runtime.

Question 54

What is the observer pattern?

Answer 54

Application of the publish-subscribe architecture.

Question 55

What is the composite pattern?

Answer 55

Promotes the use of a single uniform interface.

Question 56

What are some tips for designing user interfaces? (6 things)

Answer 56

1. identify the audience 2. what ways can a system perform a task? 3. hierarchy of user commands 4. refine the sequence of user interaction w/ system 5. designing relevant classes for the UI 6. integrating ui into the overall system.

Question 57

What is a framework?

Answer 57

A large reusable design for a specific application domain. | GUI editors, web applications, accounting systems.

Question 58

What is a uses relation?

Answer 58

a dependency relation of each software unit.