UML Behavioral Modeling 2

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Hue UniversityHue University

UML INTERACTIONUML INTERACTION

DIAGRAMSDIAGRAMS . , Dr Hoang Huu Hanh OST Hue University

hanh-at-hueuni.edu.vn


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ObjectivesObjectives

Read basic UML Interaction(communication and Sequence)Diagram notation


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IntroductionIntroduction

Why do objects exist?To perform an activity to help fulfill

a systems purpose

Interaction Diagrams are used tomodel system dynamics How do objects change state?

How do objects interact (messagepassing)?


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Communication & SequenceCommunication & SequenceDiagramsDiagramsAn Interaction Diagram is a

generalization of two specializedUML diagram types

Communication Diagrams:

Illustrate object interactionsorganized around the objects andtheir links to each other

Sequence Diagrams: Illustrateobject interactions arranged intime sequence


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Communication & SequenceCommunication & Sequence

Diagrams (2)Diagrams (2)

Both diagram types aresemantically equivalent,however, they may not show the

same information Communication Diagrams

emphasize the structuralorganization of objects, while

Sequence Diagrams emphasizethe time ordering of messages

Communication Diagrams explicitlyshow object linkages, while linksare implied in Sequence Diagrams


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Interaction Diagrams AreInteraction Diagrams Are

ValuableValuableInteraction Diagrams provide a

thoughtful, cohesive, commonstarting point for inspiration

during programmingPatterns, principles, and idioms

can be applied to improve the

quality of the InteractionDiagrams


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Common Interaction DiagramCommon Interaction Diagram

NotationNotation

class instance named instance

:Sale s1:SaleSale


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Communication DiagramsCommunication Diagrams

Objects are connected with numbered(sequenced) arrows along links todepict information flow

Arrows are drawn from the interaction

sourceThe object pointed to by the arrow is

referred to as the targetArrows are numbered to depict their

usage order within the scenarioArrows are labeled with the passed

message


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Example CommunicationExample Communication

DiagramDiagram

:ClassAInstance

:ClassBInstance

1:message1()

2:message2()

message1()


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Basic CommunicationBasic Communication

Diagram NotationDiagram NotationLink - connection path between

two objects (an instance of anassociation)

Message - represented with amessage expression on anarrowed line between objects

Sequence Number - representsthe order in which the flows areused


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Basic CommunicationBasic Communication

Diagram Notation (2)Diagram Notation (2)Conditional Message

Seq. Number [ variable = value ] :message()

Message is sent only if clauseevaluates to true

Iteration (Looping)

Seq. Number * [ i := 1..N ]:

message()

* is required; [ ... ] clause isoptional


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Sequence DiagramsSequence Diagrams

Correspond to one scenario within aUse Case

Model a single operation within aSystem over time

Identify the objects involved with eachscenario

Identify the passed messages and

actions that occur during a scenarioIdentify the required response of each

action


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Example SequenceExample SequenceDiagramDiagram

:ClassAInstance :ClassBInstance

message1()

message2()

message1()


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Example SequenceExample Sequence

Diagram: make PaymentDiagram: make Payment

:Register :Sale

:Payment

an activation box showing the focus of control

makePayment(cashTendered:)

create(cashTendered:)

makePayment(cashTendered:)

X


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Basic Sequence DiagramBasic Sequence Diagram

NotationNotationLinks - Sequence Diagrams do not

show links

Message - represented with a

message expression on anarrowed line between objects


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Basic Sequence DiagramBasic Sequence DiagramNotation (2)Notation (2)

Object Lifeline - the verticaldashed line underneath anobject

Objects do not have a lifeline untilthey are created

The end of an objects life ismarked with an X at the end of

the lifeline Passage of time is from top to

bottom of diagram


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Activation - the period of time anobject is handling a message(box along lifeline)

Activation boxes can be overlaid todepict an object invoking anothermethod on itself


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Conditional Message [ variable = value ] message()

Message is sent only if clause

evaluates to trueIteration (Looping)

* [ i := 1..N ]: message()

* is required; [ ... ] clause isoptional


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Interaction DiagramInteraction DiagramStrengthsStrengthscommunication Diagram

Space Economical - flexibility to addnew objects in two dimensions

Better to illustrate complexbranching, iteration, andconcurrent behavior

Sequence Diagram

Clearly shows sequence or timeordering of messages

Simple notation


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Interaction DiagramInteraction DiagramWeaknessesWeaknessesCommunication Diagram

Difficult to see sequence ofmessages

More complex notationSequence Diagram

Forced to extend to the right whenadding new objects; consumes

horizontal space


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ATM ClientATM ClientCollaboration Diagram for Validate PIN UseCase


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ATM ClientATM ClientSequence Diagram for Validate PIN UseCase


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ConclusionsConclusions

Beginners in UML oftenemphasize Class Diagrams.Interaction Diagrams usually

deserve more attention.There is no rule about which

diagram to use. Both are oftenused to emphasize the flexibilityin choice and to reinforce thelogic of the operation. Sometools can convert one to the

other automatically

Documents

UML Behavioral Modeling 2