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Object-Oriented Software Engineering

Prof. Moheb Ramzy Girgis

Department of Computer Science Faculty of Science

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(3) Introduction to the UML

OO Software Engineering- Prof. Moheb Ramzy Girgis Dept. of Computer Science - Faculty of Science

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Introduction to the UML

 The Unified Modeling Language (UML) is a

language for specifying, visualizing, constructing, and documenting the artifacts of software

systems, as well as for business modeling and other non-software systems.

 The UML enables OO system builders to create blueprints that capture their visions in a standard, easy-to-understand way and communicate them to others.

 The UML provides a standard design notation that

is accepted by analysts, developers, and clients.

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The Components of the UML

 The UML consists of a number of graphical elements that combine to form diagrams

 The purpose of the diagrams is to present multiple views of a system, and this set of multiple views is called a model .

 A UML model describes what a system is supposed to do. It doesn't tell how to

implement the system.

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Most common diagrams of the UML

 Class Diagram

 Object Diagram

 Use Case Diagram

 State Diagram

 Sequence Diagram

 Activity Diagram

 Collaboration Diagram

 Component Diagram

 Deployment Diagram

 Some Other UML Features

• Packages

• Notes

• Stereotypes

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Class Diagram

 A class diagram is static model that shows the classes and relationships among classes that remain constant in the system over time.

 The class icon:

name attributes operations

A class diagram consists of a number of these icons connected by lines that

show how the classes relate to one another.

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Class Diagram for Manage Appointment

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Class Diagram Syntax

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Multiplicity

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Aggregation and Generalization Associations

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Object Diagram

 An object diagram shows the objects and their relationships with one another.

 The object icon:

object name : Class name

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Use Case Diagram

 A use case is a collection of scenarios of system use.

 Every use case is initiated by an entity, called an actor , which can be a person or another system.

 The use case is a valuable tool for gathering system requirements from a user's point of view.

Actor Use case

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Use Case Diagram for Appointment

System

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Syntax for Use-Case Diagram

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Use Case Diagram for Hospital Management System



The <<include>>

relationship indicates that the use case at the arrow head is always called when the use case at the arrow tail is executed.



The <<extend>>

relationship indicates that

the use case at the arrow

head is optional. Note that

the use case at the arrow

tail is able to execute on its

own even if the extending

use case is not called.

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State Diagram

 At any time, an object is in a particular state.

 The state of an object is defined by the value of its properties and its relationships with other objects at a particular point in time.

For example, a patient might have a state of new, current or former.

 A state diagram is a dynamic model showing changes of state of a single object over time in response to events along with its responses and actions.

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State Diagram for a Hospital Patient

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Syntax for State Diagram

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Sequence Diagram

 In a functioning system, objects interact with one another, and these interactions occur overtime.

 The UML sequence diagram shows the time- based dynamics of the interaction.

 It visualizes how the objects in a system

interact with one another overtime.

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Sequence Diagram Example

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Syntax for Sequence Diagram

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Collaboration Diagram

 The UML collaboration diagram is another way of visualizing how objects work together over time.

 Objects may be anywhere in the diagram.

 Messages from one object to another appear as lines connecting the objects.

 Each line is numbered according to its placement in the sequence of messages and shows information that pertains to the nature of the message.

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A Collaboration Diagram Example

A client initiates the interaction sequence by inserting his/her card, and messages occur in the sequence represented by the collaboration diagram.

2: Verify PIN 1: Insert card 6. Enter amount to deposite 9. Enter amount to withdraw

:ATM

:Client

4: Eject card 5. Request amount 12. Close transaction

:Controller : Database

7: Deposite amount 8. Update account 10. Withdraw if balance is sufficient

3: Invalid PIN 11: Inform client if

balance is insufficient

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Activity Diagram

 The UML activity diagram shows the steps and decision points that occur within the behavior of an object, or within a business process.

 The state diagram shows the states of an object and represents activities as arrows connecting the states.

 The activity diagram highlights the activities

 Each step is a rounded rectangle and each decision point is a diamond.

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An activity diagram for the “creating and

printing a document”

activity

[tables not needed]

[tables needed]

[graphics not needed]

[graphics needed]

print(file) print(file)

Print

:Printer Open Word Processing Package

Create File

Save the File Type the Document

Open and Use Graphics Package

Open and Use Spreadsheet Save File

Print Hardcopy

Exit Office Suite

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Syntax for Activity Diagram

print(file) print(file) [graphics needed]

:Printer

Step Transition Decision point Condition Sending a signal Receiving a signal

Transition between sending and receiving a signal steps Object

The start point The end point

Symbol Purpose

Save the File

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Some Other UML Features

 The UML provides more features that enable us to organize and extend the diagrams.

Packages

 Sometimes we need to organize the elements of a diagram into a group.

 For example, in order to show that a number of classes or components are part of a

particular subsystem, we group them into a

package , represented by a tabbed folder.

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Notes

 The UML note is helpful when a part of a diagram requires some explanation.

 It is represented by a rectangle with a folded corner, and explanatory text inside it.

 The note is attached to a diagram element by connecting a dotted line from the element to the note.

Package 1

Class 1

Class 2 Class 3

A UML package

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Stereotypes

 Sometimes, the designer of a system may need some tailor-made items.

 Stereotypes enable us to take existing UML elements and turn them into new ones.

 A stereotype is represented as a name enclosed in two pairs of angle brackets («»), called

guillemets.

Class 1

Some explanatory text about class1

A UML note

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