Tài liệu Less04- Use-Case Analysis docx

Objectives: Use-Case Analysis Understand the purpose of Use-Case Analysis and where in the lifecycle it is performed  Identify the classes which perform a use- case flow of events  Di

Object Oriented Analysis and Design

Using the UML

Module : Use-Case Analysis

Objectives: Use-Case Analysis

 Understand the purpose of Use-Case Analysis and where in

the lifecycle it is performed

 Identify the classes which perform a use- case flow of

events

 Distribute the use-case behavior to those classes, identifying

responsibilities of the classes

 Develop use-case realizations that model the collaborations

between instances of the identified classes

Use-Case Analysis in Context

Designer Use-Case

Analysis

Use-Case Analysis in Context

 we have made an initial attempt at defining our

architecture we have defined the upper layers of our architecture, the key abstractions, and some key analysis mechanisms This initial architecture, along with the software requirements defined in the

Requirements workflow, guides and serves as input

to the Use-Case Analysis activity.

 In Use-Case Analysis, we identify the analysis classes

and define their responsibilities As the analysis

classes and their responsibilities are defined, we will also note the usage of any architectural (more

specifically, analysis) patterns defined in

Architectural Analysis The architectural layers and their dependencies may affect the allocation of

responsibility to the defined analysis classes.

Use-Case Modeling Guidelines

Analysis Model (optional)

Use-Case Analysis Overview

Software Architecture

Document

Requirement Capture and Analysis –Conceptual Model

 Conceptual Model – Concepts and Classes

Important and typical activity in object-oriented requirement

analysis is to identify concepts related to the requirements and to create a conceptual model of the domain

 Conceptual Model or domain model

illustrates meaningful (to the modelers) conceptual classes in a

problem domain

 A domain model OR conceptual models is a visual

representation of conceptual classes or real-world objects in

a domain of interest

Requirement Capture and Analysis –Conceptual Model (Cont.)

 The aim of this step is to decompose the problem in terms of

individual concepts or objects

 A central distinction between OOA and structured analysis is

decomposition by concepts (objects) rather than decomposition by functions

Requirement Capture and Analysis –Conceptual Model (Cont.)

Problem word

modeling

Concept model

Requirement Capture and Analysis –Conceptual Model (Cont.)

 Conceptual Models Are not Models of Software Components

they models Conceptual Classes

 The conceptual modeling process is fundamentally an

inside-out approach Inside-out means that we’re starting with the core objects in the system, then working from the inside outward, to see how those objects are going to

participate in the system we’re building

Use-Case Analysis Steps

 Supplement the Use-Case Description

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

Use-Case Analysis Steps

 Supplement the Use-Case Description

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

• The system displays a list of

course

• The system retrieves and displays a list of current course offerings from the course catalog

Supplement the Use-Case Description

 Supplement the Use-Case Description

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

Use-Case Analysis Steps

Professor name professorID: UniqueId create( )

save( ) delete( )

Class Name Attributes Operations

Class Diagrams

Sequence Diagrams

Use Case

Collaboration Diagrams

Review: Use-Case Realization

Find Classes From Use-Case Behavior

 The complete behavior of a use case has to be distributed to

analysis classes

System boundary

Use-case behavior coordination

System information

What is an Analysis Class?

<<boundary>>

<<control>>

<<entity>>

Use Cases Analysis

Classes

Source Code

Exec

Design Elements

Analysis Classes: A First Step Towards Executables

Environment Dependent

Analysis class stereotype

What is a Boundary Class?

 Intermediates between the interface and something outside

the system

 Several Types

 User interface classes

 System interface classes

 Device interface classes

 One boundary class per actor/use case pair

Model interaction between the system and its environment

Course Catalog System Register for Courses

Student

Example: Finding Boundary Classes

 One boundary class per actor/use case pair

RegisterForCoursesForm CourseCatalogSystem

Concentrate on the responsibilities, not the details!

Guidelines: Boundary Class

 User Interface Classes

 Concentrate on what information is presented to the user

 Do NOT concentrate on the UI details

 System and Device Interface Classes

 Concentrate on what protocols must be defined

 Do NOT concentrate on how the protocols will be implemented

Business-Domain Model

Environment Independent

Analysis class stereotype

Use Case

Architectural Analysis

Abstractions

What is an Entity Class?

 Key abstractions of the system

Store and manage information in the system

Example: Finding Entity Classes

 Use use-case flow of events as input

 Key abstractions of the use case

 Traditional, filtering nouns approach

 Underline noun clauses in the use-case flow of events

 Remove redundant candidates

 Remove vague candidates

 Remove actors (out of scope)

 Remove implementation constructs

 Remove attributes (save for later)

 Remove operations

Example: Candidate Entity Classes

 Register for Courses (Create Schedule)

Schedule CourseOffering

Student

Use Case

Use-case dependent, Environment independent

Analysis class stereotype

What is a Control Class?

 Use-case behavior coordinator

 One control class per use case

The Role of a Control Class

Coordinate the use-case behavior

Course Catalog System Register for Courses

Student

Example: Finding Control Classes

 One control class per use case

RegistrationController

Student Register for Courses Course Catalog System

Use-Case Model

Design Model

Example: Summary: Analysis Classes

CourseCatalogSystem StudentRegisterForCoursesForm Schedule

 Supplement the Use-Case Descriptions

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

Use-Case Analysis Steps

Sequence Diagrams Collaboration Diagrams

Distribute Use-Case Behavior to Classes

 For each use-case flow of events:

 Identify analysis classes

 Allocate use-case responsibilities to analysis classes

 Model analysis class interactions in interaction diagrams

 Responsibilities are related to the obligations of an object in

terms of its behavior

 Two types of responsibilities :

•doing something itself, such as

creating an object or doing a

calculation

•initiating action in other objects

•controlling and coordinating

activities in other objects

 knowing about private

encapsulated data

 knowing about related objects

 knowing about things it can derive

or calculate

 Responsibilities are assigned to classes of objects during object

design:

 a Sale is responsible for creating SalesLineltem

 a Sale is responsible for knowing its total

 A responsibility is not the same thing as a method, but methods

are implemented to fulfill responsibilities:

 the responsibility to “calculate a Sale" may involve only one or few methods

 Assigning responsibilities to software classes is very important:

 Easier to understand, maintain, extend and reuse

Guidelines: Allocating Responsibilities to Classes

 Use analysis class stereotypes as a guide

Guidelines: Allocating Responsibilities to Classes (cont.)

 Who has the data needed to perform the responsibility?

 One class has the data, put the responsibility with the data

 Multiple classes have the data:

• Put the responsibility with one class and add a relationship to the other

• Create a new class, put the responsibility in the new class, and add relationships to classes needed to perform the responsibility

• Put the responsibility in the control class, and add relationships to classes needed to perform the responsibility

1.1: PerformAnother Responsibility

The Anatomy of Sequence Diagrams

Hierarchical Message

Numbering

Sequence Diagrams

 Sequence diagram is an interaction diagram that

emphasizes the time-ordering of messages in an interaction

 Messages passed between objects manifest the interaction

 Sequence diagram components

 Objects

 Lifelines

 Messages

 Iteration

Sequence Diagrams

Elements

 Objects - objects that participate in the interaction

 shown as a box labeled at the top of a dashed vertical

 (Object Name)!: Class-Name

 Object lifelines - the lifetime of the object

 represents the period of time during which the object exists

 shown as vertical dashed lines from object boxes

 Activations - Focus of control

 represents the period of time during which an object is active (executing or waiting for a subroutine).

 shown as a thin rectangle on an object’s lifeline.

 Messages - communication between objects

 shown with horizontal solid arrows between object lifelines; messages may be labeled.

 message sequence is usually implicit in location of message arrows.

Example: Sequence Diagram

A list of the available

course offerings for this

semester are displayed

Student wishes to

create a new

schedule

1 // create schedule( )

5 // display course offerings( )

2 // get course offerings( )

3 // get course offerings(forSemester)

6 // display blank schedule( )

7 // select 4 primary and 2 alternate offerings( )

8 // create schedule with offerings( )

9 // create with offerings( )

Example: Collaboration Diagram

: Student

: RegisterForCoursesForm

: RegistrationController

: Schedule : Student

2 // select 4 primary and 2 alternate offerings( )

1.1 // get course offerings( ) 2.1 // create schedule with offerings( )

2.1.1 // create with offerings( )

1.1.1 // get course offerings(forSemester)

2.1.2 // add schedule(Schedule)

1.1.1.1 // get course offerings( )

Example: Collaboration Diagram (cont.)

: CourseOffering

: Student

: RegistrationController

: Schedule

: Student

: PrimaryScheduleOfferingInfob

1.1.2.2 // has pre-requisites(CourseOffering)

Alternate Flow 4 Alternate Flow 5 Alternate Flow n

AF1 AF2 AF3

Basic Flow

One Interaction Diagram Is Not Good Enough

Collaboration Diagrams Vs Sequence Diagrams

 Supplement the Use-Case Descriptions

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

Use-Case Analysis Steps

// PerformResponsibility

Supplier // PerformResponsibility

Interaction Diagram

Class Diagram

Describe Responsibilities

 What are responsibilities?

 How do I find them?

// select 4 primary and 2 alternate offerings()

// display blank schedule()

<<boundary>>

PrimaryScheduleOfferingInfo grade

// is enrolled in?() // mark as enrolled in()

<<entity>>

CourseCatalogSystem // get course offerings()

<<boundary>>

RegistrationController

// get course offerings() // submit schedule() // create schedule with offerings()

<<control>>

Student

// add schedule() // has pre-requisites()

<<entity>>

ScheduleOfferingInfo status

// mark as selected() // mark as cancelled() // is selected?()

<<entity>>

CourseOffering number : String = "100"

startTime : Time endTime : Time days : Enum // add student()

Maintaining Consistency: What to Look For

 In order of criticality

 Redundant responsibilities across classes

 Disjoint responsibilities within classes

 Class with one responsibility

 Class with no responsibilities

 Better distribution of behavior

 Class that interacts with many other classes

 Supplement the Use-Case Descriptions

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

Use-Case Analysis Steps

Attribute : Type = InitValue Attribute : Type = InitValue Attribute : Type = InitValue

CourseOffering<<entity>>

number :String=“100”

startTime : Time endTime: Time days: enum

Finding Attributes

 Properties/characteristics of identified classes

 Information retained by identified classes

 “Nouns” that did not become classes

 Information whose value is the important thing

 Information that is uniquely "owned” by an object

 Information that has no behavior

Review: What is an Association?

 The semantic relationship between two or more classifiers

that specifies connections among their instances

 A structural relationship, specifying that objects of one thing

are connected to objects of another

Simple association

is a pre-requisite of

<<entity>> Course

Whole/aggregate part

0 4 0 2

primaryCourses alternateCourses

Review: What is Aggregation?

 A special form of association that models a whole-part

relationship between an aggregate (the whole) and its parts

 The relationship is an aggregation

 If two objects are usually considered as

independent, although they are often linked

 The relationship is an association

When in doubt use association

What are Roles?

 The “face” that a class plays in the association

Review: Multiplicity

2 4 0 1 1 *

0 * 1

What does multiplicity mean?

 Multiplicity answers two questions:

 Is the association mandatory or optional?

 What is the minimum and maximum number of instances that can be linked to one instance?

<<entity>> add student to

remove student from

Example: Multiple Associations

1 0 *

1 1

Schedule // create with offerings()

<<entity>>

1 0 1

RegisterForCoursesForm // create schedule ()

// display course offerings () // display blank schedule // select 4 primary and 2 alternate offerings()

<<entity>>

currentSchedule registrant

0 1 0 1

Example: VOPC: Finding Relationships

 Supplement the Use-Case Descriptions

 For each use-case realization

 Find Classes from Use-Case Behavior

 Distribute Use-Case Behavior to Classes

 For each resulting analysis class

 Describe Responsibilities

 Describe Attributes and Associations

 Qualify Analysis Mechanisms

 Unify Analysis Classes

 Checkpoints

Use-Case Analysis Steps