OBJECT MODELING

Question 1

What is object-oriented Analysis

Answer 1

 Object-oriented (O-O) analysis describes an information system by identifying things called objects
 O-O analysis sees a system from the viewpoint of the objects themselves as they function and interact
 For example, when a patient makes an appointment to see a doctor, the patient is an object, the doctor is an object, and the appointment itself is an object

Question 2

What is the end product of O-O analysis

Answer 2

 The end product of O-O analysis is an object model, which represents the information system in terms of objects and O-O concepts
 UML will be used to develop object models

Question 3

Describe an object and how it differs from DFDs

Answer 3

 An object represents a person, a place, an event, or a transaction that is significant to the information system
 DFDs are created to treat data and processes separately. An object, however, includes data and the
processes that affect the data

Question 4

Illustrate how UML represents Objects

Answer 4

*See notes

Question 5

Describe Attributes

Answer 5

 An object has certain attributes, which are characteristics that describe the object
 Some objects might have a few attributes; others might have dozens
 Objects can inherit, or acquire, certain attributes
from other objects

Question 6

What is a state

Answer 6

 Objects can have a specific attribute called a state
 The state of an object is an adjective that describes the object’s current status
 For example, depending on the state, a bank account can be active, inactive, closed, or frozen

Question 7

Describe Methods

Answer 7

 Methods are tasks or functions that the object performs when it receives a message, or command, to do so
 For example, a car performs a method called OPERATE WIPERS when it is sent a message with the wiper control
 A method defines specific tasks that an object can perform
 Methods resemble verbs since they describe what and how an object do

Question 8

Describe object messages

Answer 8

 A message is a command that tells an object to perform a certain method
 The same message to two different objects can produce different results
 The concept that a message gives different meanings to different objects is polymorphism

*See notes for example

Question 9

Explain the black box concept in object messages and its advantages

Answer 9

 An object can be viewed as a black box, because a message to the object triggers changes within the object without specifying how the changes must be carried out
 The black box concept is an example of encapsulation, which means that all data and methods are self-contained
 A black box does not want or need outside interference, hence modularity is well accomplished

Question 10

Which programming languages are used to implement O-O designs

Answer 10

Research

Question 11

What is the major advantage of O-O designs

Answer 11

 systems analysts can save time and avoid errors by using objects, and
 programmers can translate the designs into code, then
 work with reusable program modules that have been tested and verified

Question 12

Describe a class and an instance

Answer 12

 An object belongs to a group or category called a class
-For example, Ford belong to a class called CAR
 An instance is a specific member of a class
 Many instances of the CAR class may be
observed:
-The TRUCK class, the MINIVAN class, and the
SPORT UTlLITY VEHICLE class

Question 13

Relate objects and classes

Answer 13

 All objects within a class share common attributes and methods, so a class is a blueprint or template for all the objects within the class
 Objects within a class can be grouped into subclasses, which are more specific categories within a class
 For example, TRUCK objects represent a subclass
within the VEHICLE class, along with other subclasses called CAR, MINIVAN, and SCHOOL BUS

Question 14

Describe relationships among objects and their importance

Answer 14

 Relationships describe what objects need to
know about each other, how objects respond to changes in other objects, and the effects of membership in classes, superclasses, and subclasses
 Relationships enable objects to communicate and interact as they perform business functions and transactions required by the system
 Some relationships are stronger than others

Question 15

What is the strongest relationship?

Answer 15

 The strongest relationship is called inheritance
 Inheritance enables an object, called a child, to derive one or more of its attributes from another object called a parent

Question 16

Describe the object relationship diagram and its importance

Answer 16

The model shows the objects and how they interact
to perform various function
 That model is used as a guide to continue to develop additional diagrams and documentation and to provide an overview of the system

Question 17

Describe Use Case Modelling

Answer 17

 A use case represents the steps in a specific business process
 An external entity/an actor initiates a use case by requesting the system to perform a process

Question 18

Describe and illustrate the symbols used in a use case diagram

Answer 18

 The UML symbol for a use case is an oval with a label that describes the action or event
-The actor is shown as a stick figure with a label that
identifies the actor’s role
-The line from the actor to the use case is called an association because it links a particular actor to a use case

*See notes for illustrations

Question 19

Describe and illustrate how a use case can interact with other use cases

Answer 19

 When the outcome of one use case is incorporated
by another use case, we say that the second case uses the first case
 UML indicates the relationship with an arrow that points at the use case being used

*See notes for illustrations

Question 20

How does start one create a use case

Answer 20

 To create use cases, start by reviewing the information that was gathered during the requirements engineering phase
 The objective is to identify the actors and the processes they initiate
 For each use case, develop a use case description in the form of a table

Question 21

What is contained in a use case description document

Answer 21

the name of the use case, the actor, a description of the use case, a step-by-step list of the tasks and actions required for successful completion, a description of alternative courses of action, preconditions, postconditions, and assumptions

*See notes for example

Question 22

Describe the use case diagram

Answer 22

A use case diagram is a visual summary of several related use cases within a system or subsystem

Question 22

Describe the use case diagram

Answer 22

A use case diagram is a visual summary of several related use cases within a system or subsystem

Question 23

Describe how a use case diagram is drawn

Answer 23

 When a use case diagram is created, the first step is to identify the system boundary, which is represented by a rectangle
 The system boundary shows what is included in the
system (inside the rectangle) and what is not included in
the system (outside the rectangle)
 After the system boundary is identified, use cases
are placed on the diagram, the actors are added and the relationships are shown

Question 24

Describe and illustrate class diagrams

Answer 24

 A class diagram shows the object classes and relationships involved in a use case
 Class diagrams evolve into code modules, data objects, and other system components

*See notes for illustration

Question 25

Describe and illustrate cardinality in class diagrams

Answer 25

 The class diagram includes a concept called cardinality, which describes how instances of one class relate to instances of another class
 For example, an employee might have earned no vocation days or one vacation day or many vacation days

*See notes for illustration

Question 26

Describe the sequence diagram

Answer 26

 A sequence diagram is a dynamic model of a use case, showing the interaction among classes during a specified time period
 A sequence diagram graphically documents the use case by showing the classes, the messages, and the timing of the messages

Question 27

Describe and illustrate the symbols used in sequence diagrams

Answer 27

 Sequence diagrams include symbols that represent classes, lifelines, messages, and focuses

1. A class is identified by a rectangle with the name inside. Classes send or receive messages
2. A lifeline is identified by a dashed line. The lifeline represents the time the object above it is able to interact with the other objects in the use case. An X marks the end of the lifeline
3. A message is identified by a line showing direction that runs between two objects
4. A focus is identified by a narrow vertical shape that covers the lifeline. The focus indicates when an object
   sends or receives a message

Question 28

Describe the state transition diagram

Answer 28

A state transition diagram shows how an object changes from one state to another, depending on events that affect the object
 All possible states must be documented in the state
transition diagram

Question 29

Describe and illustrate the symbols in a state transition diagram

Answer 29

 The states appear as rounded rectangles with the state names inside
 The small circle to the left is the initial state or the point where the object first interacts with the system
 Reading from left to right, the lines show direction and describe the action or event that causes a transition from one state to another
 The circle at the right with a hollow border is the final state

*See notes for illustration

Question 30

Describe the activity diagram

Answer 30

 An activity diagram resembles a horizontal flowchart
that shows the actions and events as they occur
 Activity diagrams show the order in which the actions take place and identify the outcome

Question 31

illustrate the symbols in an activity diagram

Answer 31

*see notes