system modelling with objectives describe unified modeling language (uml) in the context of...

System Modelling with

objectives

Describe Unified Modeling Language (UML) in the context of Requirements Specification

Re-visit use case, class, object and sequence diagrams

Describe collaboration, statecharts, activity, component and deployment diagrams

Modelling with UML 2

Popular Design and Modelling Tool

• Large systems are easier to understand when you break them down into subsystems

• Good modelling techniques are increasingly important as the size and complexity of systems increase

• Good models promote communication among technical and non-technical workers while ensuring good solutions

requires organisation and planning

• An Object-oriented perspective.


About it…

• Was created at Rational Software by Booch, Jacobson, and Rumbaugh. The Object Management Group adopted UML as a standard in 1997.

• Is a standard way to specify, construct, and document systems that use OO methods

• Systems you model may be implemented in an OO programming language like Java, C++, C#

• As with flowcharts, pseudocode, hierarchy charts and class diagrams, UML has its own conventions and symbols

• You can the entire specification and usage guidelines from the OMG at www.omg.org/uml/

http://www.omg.org/uml/


UML Diagrams

• Use to create top view diagrams of business processes that let you hide detail and focus on functionality

• Useful with customers who are not technically oriented

• Each type of diagram allow you to see a process from a different angle

• Diagram Types:– Use case diagrams– Class diagrams– Object diagrams– Sequence diagrams– Collaboration

diagrams– Statechart diagrams– Activity diagrams– Component diagrams– Deployment diagrams


UML diagrams classification

• Those that illustrate the dynamic, or changing, aspects of a system, and

• Those that illustrate the static, or steady aspects of a system

• Dynamic:– Use case diagrams, – Sequence diagrams, – Collaboration diagrams, – Statechart diagrams, – Activity diagrams

• Static:– Class diagrams, – Object diagrams, – Component diagrams, – Deployment diagrams.


Use case Diagrams

• Shows how a system works for the perspective of those who approach it from the outside or use it

• This includes many types of uses:– Employees, customers, suppliers– Governments, private organisations,

machines or other systems– Easier to think of them as users,

hence the term actors


Use case diagram for Librarian

• Represent system functions or services that are visible to the actor• Represent cases for which actors interact with system or benefit

from it• Determining all cases help divide a system logically into functional

parts• Establishing use cases usually follows from analysing the main

events in a system

acquireNewBook()

checkOutBook()

librarian


Variations of use cases

• Extend– Is a use case that shows functions beyond those

found in the base case

• Include– When a use case can be part of multiple use cases

(similar to subroutine or submodule)

• Generalisation– When a use case is less specific that others and you

want to be able to substitute the more specific for a general one


<<Extend>>

• Example:– Checking out a book for a new library user is

slightly more complicated that checking a book out for an existing user

acquireNewBook()

checkOutBook()checkOutBookfo

rNewUser()<<extend>>

librarian


<<include>>

• Example:– Issuing a library card might be a function of

checkOutBook() when library user is new– It might also be a function of registerNewUser()

acquireNewBook()

checkOutBook()checkOutBookfor

NewUser()<<extend>>

registerNewUser()

issueLibraryCard()

<<include>><<include>>

librarian


Use case diagram for Librarianwith Generalisations

• Example:– A librabry has procedures for acquiring new material,

acquireNewItem() is a generalisation of acquiring specific items

acquireNewBook()

checkOutBook()checkOutBookfor

NewUser()<<extend>>

registerNewUser()

issueLibraryCard()<<include>>

<<include>>

librarian

acquireNewVideo()

acquireNewJournal()


Use case diagram for Librarianwith multiple actors

• Example:– A library clerk cannot perform as many functions as a librarian; the clerk can

check out books and register new library users but cannot acquire new materials.

acquireNewBook()

checkOutBook()checkOutBookfo

rNewUser()<<extend>>

registerNewUser()

issueLibraryCard()<<include>>

<<include>>

librarian acquireNewVideo()

acquireNewJournal()

clerk


Use case diagram emphasizing actors

checkOutBook()

librarianclerk

Library staff

Library user

Adult userchild user

Cooperating library

checkOutVideo()

checkOutReferenceMaterials()


Use case diagram emphasizing System Requirements

checkOutMaterials()

Library staff

Library user

Cooperating library

RemoveOldMaterialsFromSystem()

acquireNewMaterials()

Library System

reshelveReturnedMaterials()


Class and Object Diagrams

• You can use a class diagram to illustrate the names, attributes, and methods of a class or a set of classes

• Class diagrams are more useful to programmers (than users) because they resemble code to be developed

LibraryItem

idNum

Title

author

create()

getInfo()

Book

author

create()

getInfo()

Video

runningTime

create()

getInfo()

rewind()

Showing Generalisation


Class Diagram with association relationship

• An association relationship describes the connection or link between objects that often includes information about cardinality

• Example: – one Library object

exists and it can be associated with any number of LibraryItem and LibraryUser. A LibraryUser can borrow up to 5 items.

LibraryItem

idNum

Title

create()

getInfo(idNum)

LibraryUser

idNum

Name

Address

create()

getInfo(idNum)

borrowItem()

Library

Name

directorName

Address

phoneNumber

create()

getInfo()

1 0..*

1

0..*

0..5

0..1


Class Diagram with whole-part relationship

• A whole-part (has-a) relationship describes an association in which one or more classes make up parts of a larger class (aggregation)

Library

Name

directorName

Address

phoneNumber

create()

getInfo()

PersonnelDept

deptName

Director

phoneNo

ReferenceDept

deptName

Director

phoneNo


Object Diagrams

• Are similar to Class Diagrams, but they model specific instances of classes

LibraryItem

idNum: 23456

Title: Software Engineering

LibraryUser

idNum: 19564

Name: Rana Salah

Address: XXXX

Library

Name: University of Khartoum

directorName: Mustafa Deng

Address: Gam3a Street

phoneNumber: 83 777777

create()

getInfo()


Sequence and Collaboration Diagrams

• You use a sequence diagram to show the timing of events in a single use case– the x-axis represents objects, starting from left with object or

actor that begins the action– Vertical lines represents the period of time the object

exists– the y-axis represents time, horizontal lines along it show

how objects communicate• Collaboration diagrams emphasize the organisation of

objects that participate in a system– Similar to sequence diagrams except that it contains sequence

numbers to represent the precise order of activities– They show the relationships between the objects and the order

of messages passed between them


Sequence of events from sequence diagram

BookCheckOutRecord LibraryUser Book

create(User idNum,

Book idNum

getInfo(idNum)

(userInfo)

getInfo(idNum)

(bookInfo)

(checkOutRecord)

Librarian

1.

2.

1.1

1.2

1.3

1.4


Example: Collaboration Diagram

• Collaboration diagram uses the free-form arrangement of objects as found in an Object diagram, it is a cross between an object diagram and a sequence diagram. The diagram makes it easier to see all interactions involving a particular object.

BookCheckOutRecord

LibraryUser Book

1. create(User idNum, Book idNum

1.1 getInfo(idNum) 1.2 userInfo()

1.3 getInfo(idNum)

1.4 bookInfo()

2. checkOutRecord()

Librarian


Statechart Diagrams

• These show statuses (changes in behaviour) of a class or object at different points in time.

• Example:State diagram for class Book

not borrowablereturned()

returned()

borrowable

borrowed()[not last copy]

borrowed()[last copy]

guard expression

……


Activity Diagrams

• Resembles flowcharts showing the flow of actions of a system:– Uses flowchart start and stop symbols– Use empty diamonds to represent decisions

userRequest()

retrieveBook()contactInterLibraryLoan()

checkOutBook()

Library Owns BookLibrary doesn’t Own Book


Activity Diagrams: Fork and Join

• Many real-life systems contain activities that occur simultaneously– A fork is similar to decision but defines all branches– A join reunites control flow after a fork

memberLibraryRequestBook()

querySudanULibrary()queryGezeriaULibrary()

sendBookToRequestingLibrary()

queryJubaULibrary()


Component and Deployment Diagrams

• These model physical aspects of systems:– Component diagrams

emphasize the files, database file, documents, and other components that a system’s software uses

– Deployment diagrams focus on a system’s hardware

• You use a variety of icons to symbolize software or hardware components.

• Examples:

Internet Request

Server

Printer

Console

Table

Database


Example: Component DiagramInternet RequestInternet Request

DatabaseFilled when a part can belong

to only one whole at a time;

Open when it can belong

to several

Library User

table

Book

table


Example: Deployment Diagram

InternetInternet

Console Console Console

Printer

Server A Server B


Component Diagrams in Design and Implementation

• Describes the dependencies between various software components, such as executable files, documents, and source files.– A component is represented using a rectangular box,

with two rectangles protruding from the left side

– A Dependency is used to model the relationship between two components. The notation for a dependency relationship is a dotted arrow, pointing from a component to the component it depends on.

Component


Deployment Diagrams in Design and Implementation

• Models the hardware used in implementing a system and the association between those hardware components. Components can also be shown on a Deployment diagram to show the location of their deployment. – A node represents a piece of hardware in the system.

This entity is represented by a three-dimensional cube.

– An association, drawn as a solid line between two Nodes, indicates a line of communication between the hardware elements.

Node name


Examples

Deployment diagram:• showing that the

SiteConfig component is deployed onto the Web Server and the BaseDB component is deployed on an App Server. You can also determine that the Web Server communicates with the App Server, and the App Server communicates with the Database Server and a Printer.


Examples

• Component diagram: identifies the MyWebComps assembly as being dependent on the BaseDB and SiteConfig source files.

• You can use stereotyped icons for components instead of the standard icon


Deciding which UML Diagrams to use

• Each provide a different view of a system

• Different users have different preferences

• The most important reason you use any diagram is to communicate clearly and efficiently with the people for whom you are designing the system

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system modelling with objectives describe unified modeling language (uml) in the context of...

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