Lecture 5 sequence diagram

Ramakant SoniAssistant Professor

Dept. of Computer Science

B K Birla Institute of Engineering & Technology, Pilani, India

[email protected]

2nd December 2014

14h 00-17h 00

Ramakant Soni @ EISTI Cergy 12/2/2014

1

12/2/2014Ramakant Soni @ EISTI Cergy 2

Sequence Diagram Definition

A Sequence diagram is an interaction diagram that

shows

-- how the objects and classes involved in the scenario

operate with one another.

-- the sequence of messages exchanged .


Its Significance

An organization's technical staff can find sequence

diagrams useful in documenting how a future system

should behave.

During the design phase, architects and developers

can use the diagram to force out the system's object

interactions, thus fleshing out overall system design.


Its Use

One of the primary uses of sequence diagrams is in the

transition from requirements expressed as use cases to

the next level of refinement.

Use cases are often refined into one or more sequence

diagrams.

In addition to their use in designing new systems,

sequence diagrams can be used to document how

objects in an existing system currently interact.

This documentation is very useful when transitioning a

system to another person or organization.


Targets

Objects as well as classes can be targets which means

that messages can be sent to them.

A target is displayed as a rectangle with some text in it.

Below the target, its lifeline(vertical dashed line) extends

for as long as the target exists.

Target

Lifeline


Multi Object

To show how a client interacts with the elements of a

collection, you can use a multi-object.

Its basic notation is:


Class

The basic notation for a class is:

Only class messages (e.g. shared or static methods in some

programming languages) can be sent to a class. Generally text of

a class is not underlined, which is how you can distinguish it from an

object.


Messages

Message is a named element that defines one specific

kind of communication between lifelines of an

interaction.

The message specifies not only the kind of

communication, but also the sender and the receiver.


Message Notation

A message is represented by an arrow between the life

lines of two objects.

-Self calls are also allowed

-The time required by the receiver object to process

the message is denoted by an activation-box.

A message is labeled at minimum with the message

name.


Message Types & representation


Call Message

Call message is a kind of message that represents an

invocation of operation of target lifeline.

Its type:

- Synchronous Call

- Asynchronous Call


Synchronous Call

Synchronous call typically represents operation call -

send message and suspend execution while waiting for

response. Synchronous call messages are shown with

filled arrow head.


Asynchronous Call- Send

Asynchronous call - send message and proceed

immediately without waiting for return value.

Asynchronous messages have an open arrow head.


Create Message

Create message is sent to a lifeline to create itself. It is

shown as a dashed line with open arrowhead.


Destroy Message

Delete message is sent to terminate another lifeline. The

lifeline usually ends with a cross in the form of an X at

the bottom denoting destruction occurrence.


Return Message

Reply message to an operation call is shown as a

dashed line with open arrow head (looks similar to

creation message).


Self Message

A self message can represent a

recursive call of an operation, or one

method calling another method

belonging to the same object.

It is shown as creating a nested focus

of control in the lifeline’s execution

occurrence.


Combined Fragments

A combined fragment is one or more processing

sequence enclosed in a frame and executed under

specific named circumstances.

The fragments available are:

alt- Alternative fragment models if…then…else constructs. Only one

sequence occurs on any occasion.

opt- Optional. Encloses a sequence that might or might not happen.

You can specify, in the guard, the condition under which it

occurs.

break- If this fragment is executed, the rest of the sequence is

abandoned.

Par- Parallel fragment denotes concurrent processing.


fragments

Seq - There are two or more operand fragments. Messages

involving the same lifeline must occur in the order of the fragments.

Where they do not involve the same lifelines, messages from

different fragments may be interleaved in parallel.

strict - Strict sequencing fragment encloses a series of messages

which must occur in the given order.

neg - Negative fragment encloses an invalid series of messages.

loop - Loop fragment encloses a series of messages which are

repeated.

Loop combined fragments have the properties Min and Max,

which indicate the minimum and maximum number of times thatthe fragment can be repeated. The default is no restriction.


fragments

ignore - Ignore fragment declares a message or message to be of

no interest if it appears in the current context.

consider - Consider fragment is in effect the opposite of the ignorefragment: any message not included in the consider fragment

should be ignored.

assert - Assertion fragment designates that any sequence not

shown as an operand of the assertion is invalid.


Combined Fragment Example


Interaction Operands

Interaction operand is a named element representing

the most general interaction unit. Each interaction

fragment is conceptually like an interaction by itself.

Every combined fragment contains at least one

interaction operand, which can contain messages,

interaction uses, and smaller combined fragments.

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




Interaction Operands Example


Sequence Diagram Examples

Example 1:

Order booking

scenario


Example: Facebook Authentication

Scenario:- Facebook uses OAuth 2.0 protocol framework which enables

web application (called "client"), which is usually not the FB resource

owner but is acting on the FB user's behalf, to request access to

resources controlled by the FB user and hosted by the FB server. Instead

of using the FB user credentials to access protected resources, the web

application obtains an access token.

Web application should be registered by Facebook to have an

application ID (client_id) and secret (client_secret). When request to

some protected Facebook resources is received, web browser ("user

agent") is redirected to Facebook's authorization server with application

ID and the URL the user should be redirected back to after the

authorization process.

User receives back Request for Permission form. If the user authorizes the

application to get his/her data, Facebook authorization server redirects

back to the URI that was specified before together with authorization

code ("verification string"). The authorization code can be exchanged

by web application for an OAuth access token.


If web application obtains the access token for a FB user, it can

perform authorized requests on behalf of that FB user by including the

access token in the Facebook Graph API requests. If the user did not

authorize web application, Facebook issues redirect request to the URI

specified before, and adds the error_reason parameter to notify the

web application that authorization request was denied.


Sequence

Diagram

For

Facebook

Authentication

Process


UML Diagrams for ATM: Use Case


UML Diagrams for ATM: Sequence diagram


UML Diagrams for ATM: class diagram


Exercise:

To generate sequence diagram using use case

Steps:-

1. Designate actors and business system—Who is taking part?

2. Designate initiators—Who starts interactions?

3. Describe the message exchange between actors and business

system—Which messages are being exchanged?

4. Identify the course of interactions—What is the order?

5. Insert additional information—What else is important?

6. Verify the view—Is everything correct?


Exercise: Home heating system

Home Owner

Power Up

Power Down

Change Temp.

Home Heating

Adjust Temp

Temp. High

Temp. Low

«includes»

«includes»

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Exercise: Credit card processing system Use case


Exercise: Online Shopping


References:

[1] http://www.uml-diagrams.org/

[2] http://www.wikipedia.com/UML%diagrams

[3] http://staruml.sourceforge.net/docs/user-guide%28en%29/ch05_3.html

[4] http://www.ibm.com/developerworks/rational/library/3101. html

[5] http://www.uml-diagrams.org/sequence-diagrams-examples.html

Lecture 5 sequence diagram

Education

Transcript of Lecture 5 sequence diagram