UML CLASS DIAGRAMS

UML CLASS DIAGRAMS - Transcript

CLASS CLASS DIAGRAMS
JAGADISH JOHN

WHY WHAT WHEN HOW
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WHY
Clarity in understanding the system requirements Better communication Model driven architecture Designing data base Code generation Reverse engineering Helps to develop a good software
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WHAT
A pictorial graphical representation of Names Properties Actions Relationships

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WHEN
In a software development life cycle model We have REQUIREMENTS UML DESIGN IMPLEMENTATION TESTING
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HOW

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Agenda
What is a Class Diagram Essential Elements of a UML Class Diagram Tips Development of class diagram from a use case diagram
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What is a Class Diagram
A class diagram describes the types of classes in the system and the various kinds of static relationships that exist among them A central modeling technique that runs through nearly all object oriented methods The richest notation in UML
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Essential Elements of a UML Class Diagram
Class Attributes Operations Relationships


Constraint Rules and Notes
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Associations Generalization Dependency Realization

Classes
A class is the description of a set of objects having similar attributes operations relationships and behavior
Class Name Attributes Operations

Person
name string height Integer talk walk

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Associations
A semantic relationship between two or more classes that specifies connections among their instances A structural relationship specifying that objects of one class are connected to objects of a second possibly the same class Example An Employee works for a Company
Employee Department Company

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Associations cont
Role name instructor 1 Association name instructs

Staff Member

Student

Multiplicity

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Multiplicity

Associations cont

The number of instances of the class next to which the multiplicity expression appears that are referenced by a single instance of the class that is at the other end of the association path It indicates how many objects of one class relate to one object of another class Provides a lower and upper bound on the number of instances
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Code replacement of Association

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Associations cont
Multiplicity Indicators
Exactly one Zero or more unlimited One or more Zero or one optional association Specified range Multiple disjoint ranges 1 0 1 0 1 2 4 2 4 6 8

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Visibility
Private members can only be referenced in the same class where they are declared Protected members can be referenced in the same class or any descendants of that class Package scope members can be referenced by any classes in the same UML package only Public members can be referenced directly by any class in the same or other package

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SHOWING VISIBILITY

class name attribute1 attribute2 operation1 operation2

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Aggregation
A special form of association that models a whole part relationship between an aggregate the whole and its parts
Models a is a part part of relationship
Car 2

Door Part

1

House

Whole

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Aggregation cont
In an aggregation the part classes can exist without the whole When the part classes are destroyed the whole class will continue to exist When the whole class is destroyed the part classes will still exist Aggregation tests Is the phrase part of used to describe the relationship A door is part of a car Are some operations on the whole automatically applied to its parts Move the car move the door Are some attribute values propagated from the whole to all or some of its parts The car is blue therefore the door is blue

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A strong form of aggregation

Composition

The part classes used to make up the whole class cannot exist on their own Multiplicity on the whole side must be zero or one The life time of the part is dependent upon the whole The destruction of the whole class means destruction of the part classes

Table Query

0 1

1

Database
1

Circle

Point

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Generalization
Indicates that objects of the specialized class subclass are substitutable for objects of the generalized class super class
is kind of relationship
An abstract class Generalization relationship Circle Shape
abstract

Super Class

Sub Class

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Generalization
A sub class inherits from its super class
Attributes Operations Relationships

A sub class may

Add attributes and operations Add relationships Refine override inherited operations
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Code replacement of Generalization

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Dependency
A dependency indicates a semantic relation between two or more classes in which a change in one may force changes in the other although there is no explicit association between them

Course schedule Course add c Course void remove c Course void

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Code replacement of Dependency

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Realization
A realization relationship indicates that one class implements a behavior specified by another class an interface or protocol An interface can be realized by many classes A class may realize many interfaces
class
interface

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Code replacement of Realization

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Constraint Rules and Notes
Constraints and notes annotate among other things associations attributes operations and classes

UML offers many pre defined constraints
Customer
1 total 50 may be canceled

Order

id long value 0

Constraint

Note

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Tips
Don t try to use all the various notations Don t draw models for everything concentrate on the key areas Draw implementation models only when illustrating a particular implementation technique

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LET S SEE A CASE STUDY
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A typical use case diagram

distribute electronically
include

record grades teacher
include

save grades

update grades
include

logon
include

load grades

view grades generate report cards administrator student

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Learn how to model a class diagram
Finding classes and their associations Finding attributes and operations First identify all the nouns

here we have Grades and ReportCard

Second identify all the actors
here we have teacher student and administrator

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Now we have to create a home for the use cases
Distribute Report Cards Grade Class Record Grades Grade Class Update Grades Grade Class Save Grades Grade Class Load Grades Grade Class Logon View Grades Grade Class Generate Report Cards Report Card Class

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Now relationships
A Teacher distributes the Grades A Teacher records the Grades A Teacher updates the Grades A Grade will save itself A Grade will load itself A Teacher views Grades An Administrator views Grades An Administrator generates Report Cards A Student views Grades
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After consolidation
A Teacher maintains Grades A Teacher views Grades An Administrator views Grades An Administrator generates Report Cards A Student views Grades

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maintains

contains

Teacher

Grades
displays

ReportCard

WebSite
uses

generates

Student
uses

Logon
uses

Administrator

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Now multiplicity
maintains contains

Teacher 1 1

Grades 1 1

ReportCard 1
generates

displays

1 OnlineUser
uses

WebSite

Administrator

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Grades
maintains

Teacher 1

RecordGrades 1 UpdateGrades Distribute SaveGrades LoadGrades
displays

ReportCard 1 1 Generate
generates

1

1 Administrator

OnlineUser
uses

WebSite Logon View

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Grades
maintains RecordGrades Student String Assignment String Grade Integer contains

Teacher

1 1 UpdateGrades Student String Assignment String Grade Integer 1 1
Distribute SaveGrades LoadGrades

ReportCard
Generate

1
generates displays

uses

WebSite
UserName String Password String Logon View

1 Administrator

OnlineUser

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THANK YOU

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