Lecture-03 Introduction to UML

Computer Engineering Department

Computer Engineering Department

Object Oriented Software Modeling and Design

CE 350Abdel-Karim Al-Tamimi, Ph.D.

[email protected]://faculty.yu.edu.jo/

altamimi

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Overview

• Introduction UML

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UML Definition and Usage

• UML stands for : Unified Modeling Language

• UML helps in facilitating:– Specification– Visualization– Architecture Design– Construction– Simulation and Testing– Documentation

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UML Basics

• A model helps getting an abstract idea of the objects the software product consists of and their interactions– Employ information hiding in the model

• Model’s point of view is important to determine the final shape of the diagram and the necessary information to be included –Use-case diagram vs. Class diagram

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Using Models/Diagrams

• It is easier to change models than code

• Allow non-technical team members/ clients to understand the structure of the system and be active in decision making

• Client can check if the system’s design is confined to the agreed-on requirements

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Types of Diagrams

• There are several types of diagrams :–Use-Case Diagrams– Activity Diagrams– Class Diagrams– Interaction Diagrams– State Diagrams

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Types of Diagrams

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UML: Fundamental Level

• The first level examines fundamental UML knowledge, including basic notions on class diagrams, activity diagrams, interaction diagrams, and use case diagrams, as well as various elements such as standard stereotypes and primitive types

• These basics include not only the elements visible to UML users, but also abstract UML concepts, such as Element—the base class for all UML classes in the metamodel

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Use Case Diagram: Introduction

• It lists the capabilities of the system (including their users)

• Documents the macro requirements of the system

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Borrow Book

Borrow Book

Student

Activity Diagram

• In UML an activity diagram is a version of flowchart

• Activity diagrams are used to analyze processes, or even process re-engineering

• Very helpful in understanding the overall process without indulging in technical issues

• Explains the steps (actions) the user takes to achieve a certain milestone/milestones

• There are a Start point and an End point

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Activity Diagram: Example


Leave HouseLeave House

Take ClassTake Class Wander AroundWander Around

Return to House

Return to House

Take another Class

Done for today ?

Arrive to university

End of day

Class Diagram

• Show the classes in the system and the relationships between these classes

• There are many possible class diagrams, and a single class can be shown in more than one class diagram

• Show the classes and their relationships in the best way to understand the system

• Does not explain the classes interactions, just a static view of the system


Class Diagrams: Example


StudentStudentBookBook

ReferenceReferenceMagazineMagazine

Interaction Diagrams

• Interaction diagram are categorized into:– Sequence diagrams• Models a single flow, the classes are on top

– Collaboration diagrams• Messages and classes are organized in the spatial

space, no single flow

• These diagram represent the same information using different perspectives

• Shows objects and messages between them


Interaction Diagrams – Sequence Diagram


StudentStudent BookBook LibraryLibrary

Walk to school

Access Library

Browse Book

Borrow book

Read book

Interaction Diagrams – Collaboration Diagram


BookBook

StudentStudent

LibraryLibrary

1-Walk to school5-Read book

3-Browse book4-Borrow book

2-Access library

State Diagram

• Shows the changing state of a single object as it passes through the system


WalkingWalkingLeave

the house

StudyingStudyingArrive

to School

/ take classDone

RestingRestingHave a break

Yes

UML Notations


UML Notation of Objects and Classes


ClassClass

ObjectObject

- indicates private attributes/methods+ indicates public attributes/methods# indicates protected attributes/methods~ indicates package visible attributes/methods

Notice the naming conventionBankAccount

BankAccountBankAccount

- name- balance- name- balance+ debit (int amount): void+ credit (int amount): void

+ debit (int amount): void+ credit (int amount): void

Object1 : BankAccountObject1 : BankAccount

name = John Smithbalance = 1,000name = John Smithbalance = 1,000

Object2 : BankAccountObject2 : BankAccount

name = Robert Jonesbalance = -200name = Robert Jonesbalance = -200

Visibility / Access ModifiersReview

• Public : visible to all elements that can access the contents of the namespace that owns it

• Private: only visible inside the namespace that owns it

• Protected: visible to elements that have a generalization relationship to the namespace that owns it

• Package: Any element marked as having package visibility is visible to all elements within the nearest enclosing package


UML Class Example


StudentStudent

-StudentName:String-StudentID:Integer-DOB:DateTime-GPA:Double=0.0

-StudentName:String-StudentID:Integer-DOB:DateTime-GPA:Double=0.0

+ getGPA():Double+ setName(Name:String)- CalculateGPA():Double

+ getGPA():Double+ setName(Name:String)- CalculateGPA():Double

Relationships between Classes

• There are essentially four important types of relationships between classes: –Generalization/specialization

• Inheritance– Aggregation (“part-of”)– Association

• Role and the connection between the classes– Realization

• one model element (the client) realizes the behavior that the other model element (the supplier) specifies


Generalization / Specialization Relationship


BankAccount attributes and methods are not specified

again

BankAccount attributes and methods are not specified

again

New attribute “interest” is shown in the

subclass

New attribute “interest” is shown in the

subclass

Generalization

Generalization

Specialization

Specialization

Generalization / Specialization Relationship• An abstract class is used to specify the

required behaviors (operations) of a class, without having to provide their actual implementations

• An operation without the implementation (body) is called an abstract operation

• A class with one or more abstract operations is an abstract class

• An abstract class cannot be instantiated because it does not have the required implementation of the abstract operations


Association Relationship

• Object-oriented systems are made up of objects of many classes. Associations represent relationships among classes

• An association is represented by a line drawn between the associated classes involved with an optional role name attached to either end

• The role name is used to specify the role of an associated class in the association

• If an association connects two objects instead of classes, it is called a link

• A link is an instance of an association.


Association Relationship


Name of Link

Multiplicity

Role

Name of Association

Multiplicity


UML Multiplicity Meaning

1 Exactly 1 (default)

2 Exactly 2

1..3 From 1 to 3 inclusive

3, 5 Either 3 or 5

1..* At least [1], and at most [unlimited]

* Unlimited (including 0)

0..1 Either 0 or 1

Multiplicity: Example


StudentStudent BookBook

borrows

0..1 0..5

ProfessorProfessorborro

ws

*

0..1

Qualification Relationship

• Qualification serves as names or keys that are part of the association and are used to select/qualify objects across the association at the other end

• In UML, a qualifier is used to model this association semantic, that is an association attribute whose value determines a unique object or a subset of objects at the other end of an association

• The qualifier goes at the opposite end of the association from the class of which it’s an attribute


Qualification Relationship


Account Number a single person

Account number acted as a filter

Qualification Relationship: Example


DriverDriver vehiclevehicledrives

But if he can only drive 4 wheels vehicles:


4 wheels

4 wheels

What if he can only drive his own car:


License plate

License plate

Reflexive Associations

• Relates one object of a class to another object of the same class

• In other words, a class can be associated with itself

• Reflexive associations are two types– directional – and bi-directional


Reflexive Association: Example


Reflexive Association: Example


Directional Bi-directional

Association Classes


Sometimes, it is necessary to describe an association by including some attributes which do not naturally belong to the objects involved in the association

Enrollment is an association class

Association Classes: Example


Can a person have multiple positions at the same company ?

N-ary Association


N-ary Association


3 or a Ternary association

N-ary Association


decomposed

Aggregation Relationship• Aggregation is a stronger form of association • It represents the has-a or part-of relationship• In UML, a link is placed between the “whole”

and the “parts” classes with a diamond head attached to the “whole” class to indicate that this association is an aggregation

• Multiplicity can be specified at the end of the association for each of the “part-of” classes to indicate the quantity of the constituent parts

• Typically, aggregations are not named, and the keywords used to identify aggregations are “consists of”, “contains” or “is part of”


Aggregation : Example


Aggregation: Example


CompanyCompany

warehousewarehouse SalesmanSalesman StoreStore

0..*

1..*

0..*

0..* 1..* 0..*

Composition Relationship

• A stronger form of aggregation is called composition, which implies exclusive ownership of the “part-of” classes by the “whole” class, i.e. a composite object has exclusive ownership of the parts objects

• This means that parts may be created after a composite is created, but such parts will be explicitly removed before the destruction of the composite

• It is represented using a filled diamond head


Composition: Example


Composition: Example


ReportReport

TitleTitle ColumnColumn FigureFigure

1

1

1

1..* 1..* 0..*

General Notes

• Generalization indicates "is-a” relationship

• Composition indicates “part-of” relationship

• Aggregation indicates “has-a” relationship


CarCar EngineEngine PersonPerson AddressAddress

BookBook Reference

Reference

Difference Between Aggregation and Composition

Relationships• When attempting to represent real-world

whole-part relationships, e.g., an engine is part of a car, the composition relationship is most appropriate– A department belongs to only one university

• When representing a software or database relationship, e.g., ConvertToPDF component is a part of a software library Printing, an aggregation relationship is best

• Aggregation - Without whole part can exist. Composition - Without whole part can't exit.


Dependency Relationship

• Dependency is a weaker form of relationship which indicates that one class depends on another because it uses it at some point of time

• Dependency exists if a class is a parameter variable or local variable of a method of another class– The class uses the other’s class object(s) in its

runtime– In use-case diagrams is used to indicate that a

change to the supplier might require a change to the client


Dependency Relationship: Example


ServerServer DatabaseConnectionManager

DatabaseConnectionManager<<use>>

Dependency Relationships in UML (1 of 2)

Type of Dependency

Keyword Description

Abstraction «abstraction», «derive», «refine», or «trace»

Relates two model elements, or sets of model elements, that represent the same concept at different levels of abstraction, or from different viewpoints

Binding «bind» Connects template arguments to template parameters to create model elements from templates


Dependency Relationships in UML (2 of 2)

Type of Dependency

Keyword Description

Realization «realize» Indicates that the client model element is an implementation of the supplier model element, and the supplier model element is the specification

Substitution «bind» Indicates that the client model element takes the place of the supplier; the client model element must conform to the contract or interface that the supplier model element establishes

Usage «use», «call», «create», «instantiate», or «send»

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Realization Relationship

• In this relationship, one element realizes the behavior that the other element specifies

• Usually associated with class and component diagrams

• Usually represents the relationship between an interface (abstract class) and a sub-class that implements the interface


Realization Relationship: Example


Payable<<interface>

>

Payable<<interface>

>

EmployeeEmployeeInvoiceInvoice

SalaryEmployee

SalaryEmployee

Constraints and Notes

• Constraints are an extension of the semantics of a UML element, allowing one to add new rules or modify existing ones. Sometimes it is helpful to present an idea about restrictions on attributes and associations for which there is no specific notation

• Constraints are represented by a label in curly brackets ({constraintName} or {expression}) that are attached to the constrained element


Constraints and Notes: Example


Constraints and Notes: Example


Resources

• Matt Weisfeld, The Object Oriented Thought Process, Sams Publishing, ISBN:0-672-32611-6

• M. Jesse, “UML 2.0 for dummies”, ISBN:0764526146

• P. Kimmel, “UML Demystified”, McGraw Hill, ISBN: 0-07-148671-2

• http://www.thefullwiki.org/Unified_Modeling_Language

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Resources

• Object oriented technology, By Tsang, Lau & Leung 2005, Mcgraw-Hill

• M. Chonoles and J. Schardt, UML 2 for dummies, ISBN:0764526146

• http://publib.boulder.ibm.com/infocenter/rsmhelp/v7r0m0/index.jsp?topic=/com.ibm.xtools.modeler.doc/topics/cdepend.html


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Lecture-03 Introduction to UML

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