seem3430 information systems analysis and design

SEEM3430Information Systems Analysis and Design

UML

Introduction

• In the previous lecture, you should probably learned SDLC (e.g. waterfall, agile, etc.) and should understand the importance of documentation, diagrams, etc.• Now the problem is – how to write the

documentation and draw the diagrams?

© 2021. Gabriel Fung. 2

UML

• Unified Modeling Language (UML) is a standardized general-purpose modeling language in the field of object-oriented software engineering. • The standard is managed, and was created, by OMG.

• OMG – Object Management Group – a consortium. • UML provides specifications but not implementation.

• Before a specification can be accepted as a standard by OMG, the team which proposes the specification must use the specification to bring a product within 1 year. • This prevents un-implementable standard.

• UML was in the list of OMG adopted technologies in 1997, and also the industry standard for modeling software-intensive systems.


Side Track: About Consortium

• A consortium is an association of two or more individuals, companies, organizations or governments (or any combination of these entities) with the objective of participating in a common activity or pooling their resources for achieving a common goal.• Consortium is a Latin word, meaning "partnership",

"association" or "society"• Con = "together"• Sors = "fate"• Consors = "Partner"


UML (cont’d)

• Current version is UML 2.4• It has 14 types of diagrams divided into two categories• Each category represents a different view of a model

(discuss in the next two slides)


Structure Diagrams

• Emphasize the things that must be presented in the system.• Programmers will find them very useful in writing programs

• Diagrams:• Class diagram• Object diagram• Package diagram• Component diagram• Composite structure diagram• Profile diagram• Deployment diagram


Behavior Diagrams

• Emphasize what must be happened in the system. • Non-programmers may find them useful in explaining the

system• Diagrams:• Activity diagram• State machine diagram• Use case diagram• Communication diagram (a kind of interaction diagram)• Interaction overview diagram (a kind of interaction

diagram)• Sequence diagram (a kind of interaction diagram)• Timing diagram (a kind of interaction diagram)


UML in This Course


• There are thousands of books talking about UML (each has a few hundred pages).• We will focus on the “big-picture”: discuss the core

UML components and their ideas.

Class Diagram – Overview

• Describes the structure of a system by showing the system's classes, attributes, and relationships among classes• In a class diagram, there are many classes. Each class

is represented by a box with three parts:• Top: The name of the class• Middle: The properties/attributes of

the class• Bottom: The methods of the class


Person

# name: string– age: int

+ setName(name: string)+ getName()+ setAge(age: int)+ getAge()

#, +, – are known as “visibility”. Not Mandatory.

+ Public – Private # Protected

Class Diagram Summary


Class A

Class B

Class A

Class B

Class A

Class B

Class A

Class B

Class A

Class B

Class A

Class B

Class A

Bi-Directional Uni-Directional

Reflexive

Aggregation Composition Realization Generalization

Bi-Directional Relationship


Room

– location: String– room: int

+ setLocation(name:String)+ getLocation():

Course

– name: string– code: string

+ setName(name:string)+ getName():

0..* 0..1

A classroom can be assigned to 0 to many courses

A course can be assigned to 0 or 1 classroom

It is called Multiplicity

Multiplicity Meaning

x..y x to y (x ≥ 0, y > 0), e.g. 0..1, 0..2, 2..6, …

x..* x or more

* Zero or more

n n only, e.g. 1, 4, 10, …

assignedassigned

Uni-Directional Relationship


Course

– courseCode: String– description: String:

+ setName(name: String)+ getName():

Printer

– printerID: String:

+ setJob(courseCode: String)+ getName():

0..*print

In a uni-directional association, two classes are related, but only one class knows that the relationship exists. In this example, only the Printer class knows the existence of the Course class. This allows printers know which courses they are printing , but the courses do not know they are being printed. This loosens the coupling of the objects and therefore makes the

system more adaptive to changes.

Uni-Directional Relationship (cont'd)


MyDB

:

+ connect()+ disconnect():

GameRecord

:

:

GameStage1

:

:

GameStage2

:

:

Aggregation Relationship


Building

– securityGuard: Person[]:

:

1..*has

Person

:

:

Note: A non-fill diamond indicates the relationship is “weak”, i.e. even if Building is “destroyed”, Person (i.e. security guards) will not be “destroyed”.

Building has a non-trivial class "Person"! That’s why we need to link it back!

Composition Relationship


Room

:

:

Building

– listOfRoom: Room[]:

:

1..*has

Building has another non-trivial class! That’s why we need to link it back!

Note: The diamond is “filled”, which means Room depends on Building, i.e. if the Building is “destroyed”, then all Rooms will also be “destroyed”. This type of “strong aggregation” is called Composition

Aggregation / Composition Relationship

• If necessary, we can have uni-directional relationship for aggregation/composition relationship


B

:

:

A

:

:

B

:

:

A

:

:

Reflexive Relationship


Room

# subRoom: Room

:

Building

# name: String# listOfRoom: Room[]

:

1..*has

0..*contains

A room contains some rooms, e.g. RM101 contains RM101A and RM101B

A kind of reflexive relationship.Again, it can be bi-directional or uni-directional

Staff

:

:

1supervisor

0..*supervises

A staff has one supervisorA staff supervises 0 or many staff

Generalization Relationship


Person

# name: String:

+ getName()

Student

– studentID: String

+ getGPA()

Staff

# salary: int

+ getOfficeLocation()

Professor

– housingAllowance: int

:

Admin Staff

:

:

Generalization relationship

Realization Relationship


<<interface>>Person

+ getName()

Student

– studentID: String

+ getName()

Staff

# salary: int

+ getName()

Professor

– housingAllowance: int

:

Admin Staff

:

:

Generalization relationship

Realization relationshipIt should contains nothing

Can only be + or #

• What is realization?• Realization is one of the major properties of Object

Oriented (OO) modeling, it implements an interface.• Don’t confuse with GUI (graphical user interface). This interface did

nothing with GUI.• In OO Programming, if a class is defined as an interface, it

does not have any implementation detail.• Hence, we need to write the details that are defined in the interface

in the implementing classes.• In the diagram in the previous slide, we need to write the

“getName” method in the Student Class and Staff Class.• It is the responsibility of the program designer to drop down every

single implementation issue carefully and clearly in the diagram.


Generalization vs. Realization

Object Diagram

• An object diagram in the Unified Modeling Language (UML), is a diagram that shows a complete or partial view of the structure of a modeled system at a specific time.• Do you know the differences between Class and Object?

• Object diagrams are more concrete than class diagrams, and are often used to provide examples.• An Object diagram focuses on some particular set of object

instances and attributes, and the links between the instances.


Object Diagram Example


Room

# floor: int

:

Building

# name: String# listOfRoom: Room[]

:

1..*has

ERB301 : Room

Floor: 3

ERB : Building

name = ERBlistOfRoom = Array<Room>

has

ERB401 : Room

Floor: 4has

ERB506 : Room

Floor: 5has

The corresponding Objective Diagram:

Class Diagram:

Object Diagram – More Information

• Object diagrams help clarify classes and inheritance• They are useful to demonstrate what would happen in

the system at a specific time.• Object diagram let us understand more about the system

since class diagrams can be too abstract.

• Unfortunately, UML 2.4 specification does not have a concrete definition of how it should be drawn!• So we probably stop here.


Package Diagram

• Describes how a system is split up into logical groupings by showing the dependencies among these groupings.• Used to group elements that are related and might

change together. • A package can import/access/use other packages. • Package can also be merged with other packages.


Package Diagram (cont’d)

• For example, in a Java program:

• A package is rendered as a tabbed folder:


package webShoppingCart;

import basicWebComponent;import java.io.*;import ...:

public XXX extends GeneralShoppingCart{:

}

The name of the package that we created

We need to import these packages

We try to group programs into packages for better resources management. So we also need to tell the programmers how to implement our ideas!

Web Shopping Cart

Notations

• Import• A relationship that shows the model elements in a package

which are to be imported from another package and the visibility is public

• Access• A relationship that shows the model elements in a package

which are to be imported from another package and the visibility is private, i.e. other packages that merge/import it cannot access the packages it has accessed• Note that it may be impossible to implement.

• Merge• A relationship between two packages showing that their

contents are to be combined.


Package Diagram Example


Web Shopping

MobileShopping

MailShopping

Inventory

<<import>>

package

Shopping CartPayment

<< import >><<merge>><<merge>><<import>>

<< access>>

Utility

<<import>>

Component Diagram

• Describes how a software system is split up into components and shows the dependencies among these components.• Developers find the component diagram useful because it

provides them with a high-level, architectural view of the system• Although may not be able to implement the system (too

abstract), it helps developers formalizing a roadmap for the implementation, and make decisions about task assignments.

• System administrators find component diagrams useful because they get an early view of the logical software components that will be running on their systems.


Components


A Component

Services to be providedto other components

Services requiredfrom other components

A Component

Services to be providedto other components

A Component

Services requiredfrom other components

Component Diagram Example


OrderProduct Services Customer

Product

OrderProduct

Customer Detail

Product Code

Composite Structure Diagram

• Visualizes the internal structure of a class. • Similar to component diagram but at a micro point-of-view.

• The key entities are:• Part

• A role played at runtime by an object or by a collection of objects• Port

• An interaction point that can be used to connect other parts or the environment.

• Connector• It binds entities together, allowing them to interact at runtime.

• Collaborator• Represents by dotted oval. An abstract idea.


Composite Structure Diagram Example


Search Engine

Search port

Search book

Search CD

Request port

Request Product

part

port

environment

Another Service

connector

A portDo Sth

Order Product Services

Deployment Diagram

• Describes the hardware used in system implementations and the execution environments and artifacts (e.g. software) deployed on the hardware.


Note: This is not UML standard components (for illustration purpose only)

Use Case Diagram

• Describe a set of actions (use cases) that some systems should or can perform in collaboration with one or more external users (actors). • Each use case should provide some observable and

valuable result to the user of the system.• Used to specify what the system should do but not

how the system should do.• Major elements of the use case diagram are:• Actor• Association / Relationship• Subject / System• Use case


Use Case Diagram Example

• Consider:• In a museum, visitors can purchase admission ticket

through a clerk.• Purchasing admission ticket requires a payment system,

which will be connected to a bank.• Note that purchasing admission ticket is a kind of help. • In the museum, there is a manager who will mange the

daily activities of the museum


Use Case Diagram Example (cont'd)


System

Actor

Visitor

Clerk

Bank

Buy Admission

Ticket

Payment

Seek Help

Association / relationship

Manage Museum

<<include>>

<<extend>>

MuseumManager

answer

Ask question


• Another example:• In a museum, visitors can purchase admission ticket

through a clerk.• Purchasing admission ticket requires a payment system,

which will be connected to a bank.• Note that the visitors can seek help when purchasing

admission ticket. • In the museum, there is a manager who will mange the

daily activities of the museum




Visitor

Clerk

Bank

Buy Admission

Ticket

Payment

Seek Help

Note the keyword here also

Manage Museum

<<include>>

<<include>>

MuseumManager

$$$

answer

Activity Diagram

• Graphical representations of workflows of stepwise activities and actions with support for choice, iteration and concurrency. • Constructed from a limited number of shapes,

connected with arrows. Common shapes:• Rounded rectangles represent activities;• Diamonds represent decisions;• Bars represent the start (split) or end ( join) of concurrent

activities;• A black circle represents the start (initial state) of the

workflow;• An encircled black circle represents the end (final state).


Activity Diagram Example

• Online shopping


Search item

View item

found

Not found

Add to cart

like

dislike

Continue shopping

Check out

Done shopping

Activity Diagram Example (cont'd)

• Process Order


Receive Order

Payment Problem

Send invoice

Ship order

Close Order

Payment OK

State Machine Diagram

• Describes the states and state transitions of the system• Many software systems are event-driven• They continuously wait for the occurrence of some external

or internal event such as a mouse click, a button press...

• The response to an event generally depends on the type of the event and the state of the system• E.g. if the user want to add an item to the shopping cart,

but the shopping cart module is not available (i.e., the stateof shopping cart module is down), then the user cannot perform the “add item” action.


State Machine Diagram Example

• For example, in an ATM machine, there are three states, Idle, Active and Out of Service:


State Machine of ATM

Idle

ActiveOut of Services

Put card

Take card

Damage

Fixed

Shut down

Sequence Diagram

• Sequence diagram is the most common kind of interaction diagram, which focuses on the message interchange between a number of lifelines. • A sequence diagram shows, as parallel vertical lines

(lifelines), different processes or objects that live simultaneously, and, as horizontal arrows, the messages exchanged between them, in the order in which they occur. This allows the specification of simple runtime scenarios in a graphical manner.


Sequence Diagram Example

• A simple online bank about transfer money


sd online bank

:bank:customer

Transfer Money

Response

Logout

Redirect to Homepage

Sequence Diagram Example (cont'd)

• Note that a customer should be able to have multiple transfers!


sd online bank

:bank:customer

Transfer Money

Response

Logout

Redirect to Homepage

loop


• We also want to add an option to our customers, such that they can input note before making a transfer!


Transfer Money

Response

Input reference number

loop

opt


• How about if the customer do not have enough money? We should not make the transfer!


loop

opt Refer to the previous slide

Transfer Money

Transfer OK

[enough money]

[not enough money]

Transfer fail

alt

Sequence Diagram of Facebook


Communication Diagram

• Communication diagrams show a lot of the same information as sequence diagrams, but are clearer to show the interaction among elements, whereas sequence diagrams are clearer to show the order in which the interactions take place.• Uses free-form arrangement of objects and links. To

maintain the ordering of messages, messages are labeled with a chronological number and placed near the link the message is sent. • Reading a communication diagram involves starting at

message 1.0, and following the messages from object to object.


Communication Diagram Example


:courseDetail :course

2: getCourseName(courseID): string3: getLocation(): json4: getStudentList(): array

:student

4.1: getStudentName(studentID): string4.2: getStudentMajor(studentID): string

:location

3.1: getBuildingName(locationID): string3.2: getLocationName(locationID): string

:staff

1.1: input courseID1.2: click enquiry1.3: enquiry(courseID): object

Timing Diagram

• Used to show interactions when the primary purpose of the diagram is to reason about time. • Timing diagrams focus on conditions changing within

and among lifelines along a linear time axis


Web UserIdleWaitingViewing

BrowserIdleProcessingWaiting

ServerIdleProcessing 100ms

10ms20ms

Interaction Overview Diagram

• It looks like combining activity diagrams, sequence diagrams and timing diagrams to get a big picture of the system, but each diagram contains very brief ( just enough) information.


References

• http://www.uml-diagrams.org/• http://www.uml.org/• https://creately.com/blog/diagrams/uml-diagram-

types-examples/• http://www.visual-paradigm.com/


http://www.uml-diagrams.org/

http://www.uml.org/

https://creately.com/blog/diagrams/uml-diagram-types-examples/

http://www.visual-paradigm.com/

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