Modeling behavior with Sequence diagrams

1Spring 2005Specification and Analysis of Information Systems

Session 5:

Modeling Behavior with UML Sequence Diagrams

Spring 2008

Analysis and Specification of Information Systems

Eran Tochhttp://www.technion.ac.il/~erant

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Outline

• Introduction• Basic notation• Alternating paths• Modularity

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Modeling Process

Introduction | Basics | Alternations | Modularity

Phase Actions Outcome

Initiation Raising a business needBusiness documents

Analysis Interviewing stakeholders, exploring the system environment

Organized documentation

Specification Analyze the engineering aspect of the system, building system concepts

Logical System Model

Implementation Program, build, unit-testing, integrate, documentation

Testable system

Testing & Integration

Integrate all components, verification, validation, installation, guidance

Testing results, Working sys

Maintenance Bug fixes, modifications, adaptationSystem versions

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Why to Model Behavior?

• How do we use the SMS Server interface? What is the order of executing the operations?– sendMessage, getStatus, Resend?– getStatus, sendMessage, checkForMessages?

• When do we use resend?


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Behavioral Modeling


Order of actions• How operations are

ordered• Execution Paths:

– Sequential – Parallel– Loops

Preconditions • When operations

are executed• How the outcome

of operations affects execution

Effects• What is the output

of operations• How operations

change the state of the system

Send message

Get StatusResend

[if getStutus == err]

Resend

Message queue

Adds a new msg

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Outline

• Introduction• Basic elements• Alternating paths• Modularity

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Building a Sequence Diagrams

Class AClass C

Class BClass D

Use Case 1

Use Case 2Use Case 3

Sequence diagrams capture the use-case behavior using the foundation of the classes.

Sequence = Objects + messages


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Sequence Diagrams

p : Product : ShooppingCart

addProduct (p)

customer

display)(

getPrice)(

checkout ()

sd Product Buyingobjects

message

Lifeline

activation )focus of control(

Diagram Name

• A simple sequence diagram:


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Object Control

obj1 : Class1 obj2 : Class2

do (…)

: Class3create (…)

obj1 : Class1

useroperate)( Object

Creation

Object Destruction

Return Message

foo()Messages to

self


Illustration

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Illustration

Corresponding Class Diagram

Notice that a dependency exists whenever messages are passed between instances of the class

Dependencies can be overridden by associations, aggregations etc.


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Sequences and Use-Cases

p : Product : ShooppingCart

addProduct (p)

: Ordercreate (…)

customer

display)(

getPrice)(

checkout ()


Hidden partVisible part

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Full Message Attributes

C3.1: res := getLocation )fig(

sequence number

return value

message name argument list

[sequence-expression][return-value :=] [message-name] [(argument-list)]


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Different Kinds of Messages

Synchronous Message

asynchronous Message

Return Message


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Synchronous & Asynchronous Messages

manager sensor eye

Nested Flow

check

check

operate

sensor manager alarm

Asynchronous Flow

unknown

ring

Price need to be finished, before teller can do another operation )getName(

Ring is executed, while the control flow is returned to err handle and appl

unknown

log


Example Example

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Outline


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Flow Constructs

When we tell a scenario, which types of alternatives do we need?


IfElseLoopRepeatJump

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Example

Options

archive)msg(

msg : Message :Database

opt

Do something...

[msg.status=confirmed]

Fragment

Condition


Used for modeling simple optional blocks.Has one operand; no "else" guard.

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Alternatives

archive)msg(

msg : Message :Database

Condition

:Admin

alt

notify)msg.getID)((

wait)(

[msg.status=confirmed]

[msg.status=error]

[else]

Else condition)optional(

Alternative Fragment group

Execution regions. At most one will execute.


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Loops

Display)(

: OS :Folder :File

loop

loop

Display)(

[for each Folder]

[for each File]

Loop Fragment

Condition

Nested Loop Fragment


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Breaks

isLooged = login)name,pass(

: User :User Manager : Policy

addBadLogin)name(

break

[¬isLooged]

Do something…

Do something …

If the condition is met, the break fragment is executed, and the reminder of the sequence is ignored

Handy in model exception handling


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Examples of Guards

• [for each Object]• [5]• [i=1..5]• [status = okay]• No guard means an infinite loop


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Outline


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MODULARITY

We need ways to create modular scenarios


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Referencing a diagram

login)name,pass(

: User :User Manager : Policy

Login Handling)user,pass( :bool

ref

Do something…

Do something …

Reference Gate


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Referenced Diagram

: User Manager :UserAccount

sd Login Handling

loop

cName -= getUseNamer)(

[for each UserAccount]

login)name,pass(

opt

[cName = name]

cName -= getUseNamer)(

isInSystem)true(

true

false

Diagram name

Input message

Output message


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Summary

Behavior ModelingSequence models interaction

LanguageObjects + lifeline

Messages

AlternationsLoops

Alternatives

ModularityReferencing


Modeling behavior with Sequence diagrams

Education

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