11

Advance Information Advance Information Systems Development Systems Development

(SD3043)(SD3043)Lecture 2: UML OverviewLecture 2: UML Overview

Dr. Haris MouratidisDr. Haris Mouratidisharis@uel.ac.ukharis@uel.ac.uk

33thth October 2006 October 2006

22

Last Week’s LectureLast Week’s Lecture

Introduction to the ModuleIntroduction to the Module Description of the ModuleDescription of the Module Teaching & Assessment methodsTeaching & Assessment methods Module ContentModule Content

Overview of Software EngineeringOverview of Software Engineering Definitions of Software EngineeringDefinitions of Software Engineering Concepts Concepts Development ActivitiesDevelopment Activities

33

Learning ObjectivesLearning Objectives

After this lecture you should be able to:After this lecture you should be able to: Understand UML concepts Understand UML concepts Understand UML notationsUnderstand UML notations Use UML to model information systemsUse UML to model information systems

44

Lecture LayoutLecture Layout

NotationNotation An introduction to the Unified Modeling An introduction to the Unified Modeling

Language (UML)Language (UML) An overview of UMLAn overview of UML

Use Case DiagramsUse Case Diagrams Class DiagramsClass Diagrams Interaction diagramsInteraction diagrams Statechart DiagramsStatechart Diagrams Activity DiagramsActivity Diagrams

ConclusionConclusion

55

NotationNotation

According to the “hyper dictionary” According to the “hyper dictionary” notationnotation is is defined as a technical system of symbols used to defined as a technical system of symbols used to represent special thingsrepresent special things

Notation enable us to articulate complex ideas Notation enable us to articulate complex ideas preciselyprecisely In large projects accuracy and clarity are vitalIn large projects accuracy and clarity are vital

A notation should A notation should Have well defined semanticsHave well defined semantics Be well suited for representing a given aspect of a systemBe well suited for representing a given aspect of a system Be well understood among project participantsBe well understood among project participants

66

An introduction to UMLAn introduction to UML

Object Modeling Technique (OMT) Booch Method

Object Oriented Software Engineering (OOSE)

Coad and Yourdon

Martin and Odell

UML Shlaer and Mellor

Result of the unification

Has influenced

THE GOAL:

Provide a standard notation that can be used by all object-oriented methods to model Object Oriented

Systems

77

An introduction to UML (II)An introduction to UML (II)

UML has been designed for a broad range UML has been designed for a broad range of applicationsof applications

Introduce only five diagramsIntroduce only five diagrams Use Case DiagramsUse Case Diagrams Class DiagramsClass Diagrams Interaction DiagramsInteraction Diagrams Statechart DiagramsStatechart Diagrams Activity DiagramsActivity Diagrams

88

Use Case DiagramsUse Case Diagrams A use case diagram A use case diagram

Describes the functional behavior of the system (as seen by Describes the functional behavior of the system (as seen by the users)the users)

Defines the boundaries of the systemDefines the boundaries of the system Displays the relationships between actors and use casesDisplays the relationships between actors and use cases

ActorActor A user or another system that will interact with the system A user or another system that will interact with the system

under development under development Use CaseUse Case

an external view of the system that represents some an external view of the system that represents some functionality of the system (an action the user might perform)functionality of the system (an action the user might perform)

System BoundarySystem Boundary Defines the scope of the systemDefines the scope of the system

99

Use Case descriptionUse Case description

A use case is initiated by an actorA use case is initiated by an actor A use case should have:A use case should have:

Unique Name Unique Name Participating actorsParticipating actors Entry/Exit Condition Entry/Exit Condition Flow of Events Flow of Events Describe ExceptionsDescribe Exceptions Describe Special Requirements (Constraints, Describe Special Requirements (Constraints,

Nonfunctional Requirements)Nonfunctional Requirements)

1010

Graphical RepresentationGraphical Representation

Login

Actor

Use Case

Boundary(optional)

Library System

1111

Use Case Relationships Use Case Relationships

CommunicationCommunication Denote access to functionalityDenote access to functionality Only relationship between actors and use Only relationship between actors and use

casescases Depicted by solid line between actor and use Depicted by solid line between actor and use

casecase

Login

1212

Include RelationshipInclude Relationship

Include (uses)Include (uses) in an in an includeinclude relationship, a use case includes relationship, a use case includes

the functionality described in another use the functionality described in another use case as a part of its processcase as a part of its process

Adds extra behaviour into a base use case Adds extra behaviour into a base use case Include reduces complexity Include reduces complexity Depicted by a dashed open arrow originating Depicted by a dashed open arrow originating

from the base use case and labelled with the from the base use case and labelled with the stereotype “<<include>>”stereotype “<<include>>”

1313

Include Relationship (II)Include Relationship (II)

Passenger

PurchaseMultiCard

PurchaseSingleTicket

CollectMoney

<<include>>

<<include>>

1414

Extend RelationshipExtend Relationship

ExtendExtend Adds extra functionalityAdds extra functionality A use case extends another use case by adding A use case extends another use case by adding

eventsevents Extend is also used to model exception cases, Extend is also used to model exception cases,

helps, errors, and other unexpected conditionshelps, errors, and other unexpected conditions Depicted by a dashed arrow (similar to the Depicted by a dashed arrow (similar to the

include), originating from the child (extend) use include), originating from the child (extend) use case and labelled with the stereotype case and labelled with the stereotype "<<extend>>""<<extend>>"

1515

Extend Relationship (II)Extend Relationship (II)

Passenger

PurchaseMultiCard

PurchaseSingleTicket

CollectMoney

<<include>>

<<include>>

Cancel

<<extends>>

NoChange

<<extends>>

1616

Use Case diagram testing Use Case diagram testing questionsquestions

Is our notation correct?Is our notation correct? Are all actors identified? Are all actors identified? Can the system described actually be built? Can the system described actually be built? Are all the system's functional requirements Are all the system's functional requirements

reflected in the use cases? reflected in the use cases? Do the use cases define all the functionality within Do the use cases define all the functionality within

the scope of the system and nothing outside the the scope of the system and nothing outside the scope? scope?

Can we trace each use case back to its Can we trace each use case back to its requirements? requirements?

1717

Use Case diagram guidelinesUse Case diagram guidelines Do have a clear idea of the system you intend to Do have a clear idea of the system you intend to

describedescribe Do ensure all use cases provide value to at least one Do ensure all use cases provide value to at least one

actoractor Do involve a “user” in the writing process. It is users’ Do involve a “user” in the writing process. It is users’

requirementsrequirements Do not believe anyone telling you use case Do not believe anyone telling you use case

modelling is simple…It is not!!!modelling is simple…It is not!!! Do not include system design elements in the use Do not include system design elements in the use

casescases Do not get worked up about <<extend>>, Do not get worked up about <<extend>>,

<<include>>!<<include>>! Do not forget actors representing other systems!Do not forget actors representing other systems!

1818

Class DiagramClass Diagram

Represent the structure of a system in terms of Represent the structure of a system in terms of classesclasses A class is a collection of objectsA class is a collection of objects Classes have a name, attributes, operations and Classes have a name, attributes, operations and

relationships.relationships. Class names start with uppercase letterClass names start with uppercase letter

The name of the class

The attributes of the class

The operations (methods) of the class

1919

Developing a class diagramDeveloping a class diagram

Not right or wrong techniqueNot right or wrong technique One techniqueOne technique

Pick all the nouns (person, place, thing) and Pick all the nouns (person, place, thing) and noun phrases from the requirements noun phrases from the requirements

Discard any inappropriate candidatesDiscard any inappropriate candidates Redundant, event, operation, attribute, outside the Redundant, event, operation, attribute, outside the

scope of the systemscope of the system

Practice!Practice!

2020

AssociationsAssociations

Associations depict relationships between classesAssociations depict relationships between classes If classes correspond to nouns, associations If classes correspond to nouns, associations

correspond to verbscorrespond to verbs Two typesTwo types

BidirectionalBidirectional Unidirectional: an arrow indicates the directionUnidirectional: an arrow indicates the direction

Student ModuleIs taking

Student ModuleIs taking

Bidirectional Unidirectional

2121

AggregationAggregation

Special case of associationSpecial case of association It indicates a whole-part (It indicates a whole-part ( is part ofis part of) relationship) relationship Denoted by a hollow diamond at the end of the Denoted by a hollow diamond at the end of the

wholewhole

CompositionComposition is a special case of aggregation is a special case of aggregation The whole owns its part (if whole is destroyed The whole owns its part (if whole is destroyed

the part is destroyed)the part is destroyed)

Degree Module

Window Menu

2222

Inheritance (generalization)Inheritance (generalization)

Relationship between a general class Relationship between a general class (superclass) and a more specialised one (superclass) and a more specialised one (subclass)(subclass)

It is an “is a” relationshipIt is an “is a” relationship It enables us to describes all the attributes It enables us to describes all the attributes

and operations that are common to a set of and operations that are common to a set of classesclasses

Denoted by a hollow Denoted by a hollow triangle at the end triangle at the end of the superclass of the superclass

Button

OK ButtonCancel Button

2323

MultiplicityMultiplicity

Indicate the number of links that can Indicate the number of links that can legitimate originate from an instance of a legitimate originate from an instance of a class connected to the association endclass connected to the association end

Label the association end by a set of integersLabel the association end by a set of integers Three common typesThree common types

One-to-OneOne-to-One One-to-ManyOne-to-Many Many-to-ManyMany-to-Many

PoliceStation

Police Officer

1 1..*

2424

Class Diagram testing questionsClass Diagram testing questions

Does each class define attributes, Does each class define attributes, methods, relationships, and multiplicity? methods, relationships, and multiplicity?

Is each association well named? Is each association well named? Is each association’s and aggregation’s Is each association’s and aggregation’s

multiplicity correct?multiplicity correct? Is each class named with a strong noun? Is each class named with a strong noun? Have all redundant, irrelevant, or vague Have all redundant, irrelevant, or vague

classes been removed from the diagram? classes been removed from the diagram?

2525

Class diagram guidelinesClass diagram guidelines Use singular names because each class represents Use singular names because each class represents

a generalised version of a singular objecta generalised version of a singular object Use simple class names (Student instead of …Use simple class names (Student instead of …

PersonWhoStudies)PersonWhoStudies) Do not model actors in class diagramsDo not model actors in class diagrams Use full names for attributes Use full names for attributes Make sure you class diagram is consistent with the Make sure you class diagram is consistent with the

requirementsrequirements Try to avoid using only * for multiplicity (Is it 0..* or Try to avoid using only * for multiplicity (Is it 0..* or

1..*)1..*)

2626

Quiz time!!!Quiz time!!!

Consider an ATM System. Which of the Consider an ATM System. Which of the following is NOT an actor.following is NOT an actor.A.A. CustomerCustomer

B.B. Central Bank computerCentral Bank computer

C.C. ATM processorATM processor

D.D. ThiefThief

2727

Question 2-1Question 2-1

Which of the following use case diagrams is Which of the following use case diagrams is NOT correct (if any)NOT correct (if any)

Passenger

PurchaseMultiCard

PurchaseSingleTicket

2828

Question 2-2Question 2-2

Passenger

PurchaseMultiCard

PurchaseSingleTicket

CollectMoney

<<include>>

<<include>>

Cancel

<<extends>>

NoChange

<<extends>>

2929

Question 2-3Question 2-3

Passenger

PurchaseTicket

OutOfOrder

<<extends>>

Cancel

<<extends>>TimeOut

<<extends>>

3030

Interaction diagramsInteraction diagrams Used to describe Used to describe communicationcommunication between between

interacting objects (and actors)interacting objects (and actors) Communication takes place through Communication takes place through

messagesmessages Interaction diagrams should be used when Interaction diagrams should be used when

you want to look at the behaviour of several you want to look at the behaviour of several objects within a single use case.objects within a single use case.

3131

Interaction Diagrams (II)Interaction Diagrams (II)

Two typesTwo types SequenceSequence: focus on the order that : focus on the order that

messages sent messages sent CollaborationCollaboration: focus on the relationship : focus on the relationship

between the objectsbetween the objects

3232

Sequence diagramsSequence diagrams

Sequence diagramsSequence diagrams describe interactions describe interactions among classes in terms of an exchange of among classes in terms of an exchange of messages over time messages over time

During requirements analysisDuring requirements analysis Refine use case descriptions, find additional Refine use case descriptions, find additional

objectsobjects During designDuring design

Refine interfacesRefine interfaces Sequence diagrams are Sequence diagrams are NOTNOT useful for useful for

showing the behaviour within an object showing the behaviour within an object

3333

Sequence diagram (II)Sequence diagram (II)

selectZone()

pickupChange()

pickUpTicket()

insertCoins()

PassengerTicketMachine

ActorObject

lifeline

message

Active (activation)

3434

Creation & DestructionCreation & Destruction

ChangeProcessor

Ticket

createTicket(selection)

free()

Creation

Destruction

print()

3535

Message TypesMessage Types

[Taken from Smartdraw.com]

3636

Sequence diagram testing questionsSequence diagram testing questions Does each object required for the interaction appear Does each object required for the interaction appear

on the diagram? on the diagram? Have all objects not required in the interaction been Have all objects not required in the interaction been

removed from the diagram? removed from the diagram? Does each object’s lifeline begin and end at the Does each object’s lifeline begin and end at the

proper time? proper time? Is each object’s activation described properly? Is each object’s activation described properly? If the object’s lifetime terminates, is it indicated with If the object’s lifetime terminates, is it indicated with

an X? an X? Is each use case represented by at least one Is each use case represented by at least one

sequence diagram? sequence diagram? Does each actor appear on at least one sequence Does each actor appear on at least one sequence

diagram? diagram?

3737

Sequence diagram guidelines Sequence diagram guidelines Start the message flow of a sequence diagram in the Start the message flow of a sequence diagram in the

top-left cornertop-left corner Have in mind that a message that appears lower in the Have in mind that a message that appears lower in the

diagram is sent after one that appears above itdiagram is sent after one that appears above it Arrange your actors, classes across the top of the Arrange your actors, classes across the top of the

diagram in such a way as to depict message flow from diagram in such a way as to depict message flow from left to rightleft to right

Make sure the actors that appear on the sequence Make sure the actors that appear on the sequence diagrams have the same name as on the use case diagrams have the same name as on the use case diagramsdiagrams

3838

Sequence Diagram guidelines (II)Sequence Diagram guidelines (II)

Have in mind that an actor CAN have the Have in mind that an actor CAN have the same name as a classsame name as a class

Include a description of the logic you are Include a description of the logic you are modellingmodelling

Model proactive (activate the sequence) Model proactive (activate the sequence) actors, classes on the left-hand side of the actors, classes on the left-hand side of the diagramdiagram

Model reactive (system initiates interaction Model reactive (system initiates interaction with) actors on the right-hand side of the with) actors on the right-hand side of the diagramdiagram

3939

Collaboration diagramsCollaboration diagrams

Depict the same information as sequence Depict the same information as sequence diagramsdiagrams

It shows the objects and their association It shows the objects and their association with other objects in the system apart from with other objects in the system apart from how they interact with each other. how they interact with each other.

Represent the sequence of messages by Represent the sequence of messages by numbering the interactionsnumbering the interactions+More compact diagramMore compact diagram- More difficult to followMore difficult to follow

4040

Collaboration Diagram ExampleCollaboration Diagram Example

4141

Statechart diagramsStatechart diagrams

Useful for describing the behaviour of Useful for describing the behaviour of individual objects over the full set of use individual objects over the full set of use cases that affect those objects cases that affect those objects

Statechart diagrams describeStatechart diagrams describe All of the states that an object can have, All of the states that an object can have, The events under which an object changes state The events under which an object changes state

(transitions), (transitions), The conditions that must be fulfilled before the The conditions that must be fulfilled before the

transition will occur (guards), transition will occur (guards), The activities undertaken during the life of an The activities undertaken during the life of an

object (actions).object (actions).

4242

Elements of StatechartsElements of Statecharts Initial stateInitial state

The object’s initial stateThe object’s initial state StatesStates

A condition during the life of an object in which it satisfies some A condition during the life of an object in which it satisfies some condition, performs some action, or waits for some eventcondition, performs some action, or waits for some event

TransitionsTransitions The change of state within an object The change of state within an object

EventsEvents An occurrence (signal from outside the system, invocation from inside An occurrence (signal from outside the system, invocation from inside

the system, passage of designated period of time) that may trigger a the system, passage of designated period of time) that may trigger a state transition. state transition.

ActionAction One or more actions taken by an object in response to a state change One or more actions taken by an object in response to a state change

GuardGuard A Boolean expression which, if true, enables an event to cause a A Boolean expression which, if true, enables an event to cause a

transitiontransition Final stateFinal state

The object’s final stateThe object’s final state

4343

An example: A telephone classAn example: A telephone class

Idle Active

Initial State

State

Transition

/play dial tone

Event Guard

Action

On hook

Off

Final State

Off hook [signal OK] Active

Entry/play dial tone

4444

Statechart diagram testing Statechart diagram testing questionsquestions

Does each state-transition diagram have one Does each state-transition diagram have one and only one initial state? and only one initial state?

Does each state have at least one exit Does each state have at least one exit transition? transition?

If multiple guards exist for a single event, are If multiple guards exist for a single event, are the guards mutually exclusive? the guards mutually exclusive?

Is each state and transition clearly named? Is each state and transition clearly named? Are all of the required states, events, guards, Are all of the required states, events, guards,

transitions, and actions shown on the transitions, and actions shown on the diagram? diagram?

4545

Statechart diagrams guidelinesStatechart diagrams guidelines

Make sure that each statechart diagram Make sure that each statechart diagram refers to only one class!refers to only one class!

You do not have to develop a statechart You do not have to develop a statechart diagram for every class (unless you told diagram for every class (unless you told so)so)

All statechart diagrams should have an All statechart diagrams should have an initial state (the state the class is when it is initial state (the state the class is when it is created)created)

4646

Activity DiagramsActivity Diagrams Activity diagrams describe the workflow behaviour of a Activity diagrams describe the workflow behaviour of a

system system An Activity diagram is a dynamic diagram that shows the An Activity diagram is a dynamic diagram that shows the

activity and the event that causes the object to be in the activity and the event that causes the object to be in the particular state particular state

However, activity diagrams should not take the place However, activity diagrams should not take the place of interaction diagrams and state chart diagrams. Activity of interaction diagrams and state chart diagrams. Activity diagrams do not give detail about how objects behave or diagrams do not give detail about how objects behave or how objects collaborate how objects collaborate

A State diagram shows the different states an object is in A State diagram shows the different states an object is in during the lifecycle of its existence in the system, and the during the lifecycle of its existence in the system, and the transitions in the states of the objects. These transitions transitions in the states of the objects. These transitions depict the activities causing these transitions, shown by depict the activities causing these transitions, shown by arrowsarrows

An Activity diagram talks more about these transitions and An Activity diagram talks more about these transitions and activities causing the changes in the object states activities causing the changes in the object states

4747

Activity Diagram ElementsActivity Diagram Elements

Initial ActivityInitial Activity The initial activity of the workflowThe initial activity of the workflow

ActivityActivity A state of doing something.A state of doing something.

TransitionTransition Progression to the next activityProgression to the next activity

Synchronisation bar (fork or join)Synchronisation bar (fork or join) Describes concurrent activitiesDescribes concurrent activities

Decision diamond Decision diamond Indicates decisions and the available optionsIndicates decisions and the available options

Final ActivityFinal Activity The final activity of the workflowThe final activity of the workflow

4848

Example of activity diagramExample of activity diagram

Take bus Take cab

Attend Lecture

Get Dressed

Read NewspaperHave breakfast

[In time for bus] [Not In time for bus]

Activity

Synch. Bar (fork)

Synch. Bar (join)Decision diamond

Decision option

Initial Activity

Final Activity

Transition

4949

Swim lanesSwim lanes

Enable developers to indicate which actor Enable developers to indicate which actor performs which activityperforms which activity

The diagram is partitioned in such a way The diagram is partitioned in such a way that we can indicate who/what is that we can indicate who/what is performing the activity performing the activity

Partitions called “swim lanes”Partitions called “swim lanes”+Useful because they provide more informationUseful because they provide more information- The diagram becomes largerThe diagram becomes larger

5050

Example of swim lanesExample of swim lanes

[Taken from prestwood.com]

5151

Quiz timeQuiz time

Which of the following diagrams you Which of the following diagrams you would use to show the behaviour of an would use to show the behaviour of an object?object?A.A. SequenceSequence

B.B. CollaborationCollaboration

C.C. StatechartStatechart

D.D. ActivityActivity

5252

Question 2Question 2

Which of the following diagrams you Which of the following diagrams you would use to describe communication would use to describe communication between interacting objects along with between interacting objects along with their relationships?their relationships?A.A. Sequence Sequence

B.B. CollaborationCollaboration

C.C. StatechartStatechart

D.D. ActivityActivity

5353

Question 3Question 3

Receive Payment

Close Order

Receive Order

Send InvoiceFill Order

Which of the following applies to the diagram below

A) The diagram is correct

B) The diagram is not correct

5454

ConclusionConclusion

NotationNotation An introduction to the Unified Modeling An introduction to the Unified Modeling

Language (UML)Language (UML) An overview of UMLAn overview of UML Reading list: Chapter 2 (essential), any Reading list: Chapter 2 (essential), any

book about UMLbook about UML Next week: Requirements Elicitation and Next week: Requirements Elicitation and

AnalysisAnalysis

5555

AnnouncementsAnnouncements

Problem with WebCT you can find info on Problem with WebCT you can find info on http://homepages.uel.ac.uk/H.Mouratidis/Shttp://homepages.uel.ac.uk/H.Mouratidis/SD3043D3043

If you haven’t got a handbook get one If you haven’t got a handbook get one from Godfried or download one from the from Godfried or download one from the above linkabove link

Pick up your assignmentPick up your assignment Practicals only some weeksPracticals only some weeks