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Module 1 Introduction

Module 2 Use case diagram

Module 3 Flow of events

Module 4 Realization of the class diagram

Module 5 Sequence diagram and Collaboration Diagram

Module 6 Class diagram and refinement attributes

Module 7 State transition and activity diagram

Module 8 Implementation diagram

Module 9 Component diagram and Deployment diagram

Module 10 Understanding project culture

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What is a model? ◦ A model is a simplification of reality

Why do we model? ◦ help visualizing

◦ permit specification

◦ provides a template

◦ document decisions

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Choose your models well

Every model may be expressed at various levels of precision

The best models are connected to reality

No single model is sufficient

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DEFINITION:The application of systematic, disciplined and qualifiable approach to the development, operation and maintenance of a software system is software engineering.

Software development life cycle has following stages:

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REQUIREMENT

ANALYSIS

DESIGN

IMPLEMENTATION

TESTING

Analysis & design 40 %

Development 20 %

Testing 40 %

Analysis - What is to be done ?

Design - How it is to be done ?

Two Popular methodology approaches are:

Structured Analysis & Design

Object Oriented Analysis & Design-OO model

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The object oriented approach is a way of thinking about a problem using real world concepts instead using adhoc function concepts.

We intent to learn OOAD approach for the following reason:

◦Promotes better understanding of user requirements

◦Leads cleaner design

◦Design flexibility'

◦Decomposition of the system is consistent

◦Facilitates data abstraction & information hiding

◦Software reuse

◦Easy maintenance

◦Implementation flexibility

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Following are three elements for every OO methodology:

Notation Process / Method Tool

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Notation:

It is collection of graphical symbols for expressing model of the system.

The Unified Modeling Language [UML] provides a very robust set of notation which grows from analysis to design.

By unifying the notations used by these object oriented methods, the unified modeling language provides the basis for a de facto standard in the domain of object oriented analysis and design founded on a wide base of user experience.

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It is a Unified Modeling Language, which is mainly a collection of graphical notation that methods use to express the designs.

The UML is language for visualizing, specifying, constructing and documenting the artifacts of software system.

UML is visual modeling language for modeling systems and is non proprietary.

It is an evolutionary step, which is more expressive and more uniform than individual notations.

Whitehead says

“ By relieving the brain of unnecessary work, a good notation, sets it free to concentrate on more advance and creative problems “ UML is not a method or process but is the means to express the same.

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System of several different kinds, absolutely anywhere everywhere.

Primarily for software intensive systems like:

Systems software

Business processes

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Captures business processes

Enhance communication and ensures the right communication

Capability to capture the logical software architecture independent of the implementation language

Manages the complexity

Enables reuse of design

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UML things:

Class, component, node, relationship, package etc..

UML diagrams:

Use case diagram, interaction diagram, class diagram, State diagram, deployment diagram

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What is Process?

It is an extensive set of guidelines that address the technical and organizational aspects of software development focusing on requirements, analysis and design.

Process basically encapsulates the activities leading to the orderly construction of system model.

OO model supports the iterative and incremental model for the process.

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Develop software iteratively

Manage requirements

Use component based architectures

Visually model software

Verify S/W quality

Control changes to software.

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It is automated support for every stage of software development life cycle.

Since we are concentrating on requirement, analysis and design phase, following are the names of few tools which are greatly in use:

1. Rational Rose

2. Cayenne

3. Platinum

4. Select

5. RSA

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Helps designer for creating designs much more quickly.

Supports validations like:

Consistency checking

Completeness checking

Constrain checking.

Time required for certain operation could be predicted .

Code generation

Reverse engineering.

Conversion from SSAD to OOAD

Quick documentation…etc

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All three components play equally important role towards the success of the project.

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Notation

Method Tool

Get introduced with Unified Modeling Language and know the basic components of software development life cycle.

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STATIC MODEL

DYNAMIC MODEL

PHYSICAL MODEL

LOGICAL MODEL

The models of Object Oriented Development

4+1 view of OO model.

◦ Process view

◦ Deployment view

◦ Logical view

◦ Dynamic view

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◦ Use case view

As shown in the model , for each dimension we define a number of diagrams that denote a view of the system’s model.

The use case view is central since its contents drive the developments of other views.

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1. Use case diagram

2. Class Diagram

3. Behavioral diagrams

- State chart diagrams

- Activity diagrams

- Interaction diagrams

- Sequence diagrams

- Collaboration diagrams

4. Implementation diagrams - Component diagram

- Deployment diagram

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Use case diagrams represent the functions of a system from the user’s point of view.

Sequence diagrams are a temporal representation of objects and their interactions.

Collaboration diagrams are a spatial representation of objects, links, and interactions.

Object diagrams represent objects and their relationships, and correspond to simplified collaboration diagrams that do not represent message broadcasts.

Class diagrams represent the static structure in terms of classes and relationships.

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Contd...

State chart diagrams represent the behavior of a class in terms of states

Activity diagrams are to represent the parallel behavior of an operation as a set of actions.

Component diagrams represent the logical components of an application.

Deployment diagrams represent the deployment of components on particular pieces of hardware.

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A use case diagram establish the capability of the system as a whole.

Components of use case diagram:

Actor

Use case

System boundary

Relationship

Actor relationship

Semantic of the components is followed.

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What is an actor?

An actor is some one or something that must interact with the system under development

UML notation for actor is stickman, shown below.

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Customer Manager Cashier

More about an actor:

It is role a user plays with respect to system.

Actors are not part of the system they represent anyone or anything

that must interact with the system.

Actors carry out use cases and a single actor may perform more

than one use cases.

Actors are determined by observing the direct uses of the system.

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Contd…

Those are responsible for its use and maintain as well as other systems that interact with the developed system.

An actor may

- input information to the system.

- receive information from the system.

- input to and out from the system.

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How do we find the actor?

Ask following questions to find the actors:

◦ Who uses the system?

◦ Who installs the system?

◦ Who Starts up the system?

◦ What other systems use this system?

◦ Who gets the information from the system?

◦ Who provides information to the system?

Actor is always external to the system. They are never part of the system to be developed.

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4-Categories of an actor:

Principle : Who uses the main system functions.

Secondary : Who takes care of administration & maintenance.

External h/w : The h/w devices which are part application

domain and must be used.

Other system: The other system with which the system must

interact.

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Note:

If newly identified actor is using a system in a same way like an

existing actor, then new actor can be dropped.

If two actors use system in the same way they are same actors.

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What is USE case?

A use case is a pattern of behavior, the system exhibits

Each use case is a sequence of related transactions performed by an actor and the system in dialogue.

USE CASE is dialogue between an actor and the system.

Examples:

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Open new account Withdrawal of cash

from ATM

More about USE CASE:

It is a snapshot of one aspect of system.

They model a dialog between actor and system.

A use case typically represents a major piece of functionality that is

complete from beginning to end.

Most of the use cases are generated in initial phase, but you find

some more as you proceed.

A use case may be small or large. It captures a broad view of a

primary functionality of the system in a manner that can be easily

grasped by non technical user.

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Contd…

A use case must deliver something of value to an actor.

The use cases may be decomposed into other use cases.

Use cases also present a good vehicle for project planning.

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How do we find the use cases?

What functions will the actor want from the system?

Does the system store information? What actors will create, read, update. Or delete that information?

Does the system need to notify an actor about changes in its internal state?

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Generic format for documenting the use case:

- Pre condition: If any

◦ Use case : Name of the case.

◦ Actors : List of actors(external agents), indicating who

initiates the use case.

◦ Purpose : Intention of the use case.

◦ Overview : Description.

◦ Type : primary / secondary.

◦ Post condition: If any

Typical Course of Events:

ACTOR ACTION : Numbered actions of the actor.

SYSTEM RESPONSE : Numbered description of system responses.

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USE CASE documentation example:

The following use case describes the process of opening a new account in the bank.

Use case :Open new account

Actors :Customer, Cashier, Manager

Purpose :Like to have new saving account.

Description :A customer arrives in the bank to open the new

account. Customer requests for the new account

form, fill the same and submits, along with the

minimal deposit. At the end of complete successful

process customer receives the passbook.

Type :Primary use case.

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Those use case functionality which are directly dependent on the system environment are placed in interface objects

Those functionality dealing with storage and handling of information are placed in entity objects

Functionality's specific to one or few use cases and not naturally placed in any of the other objects are placed in control objects

By performing this division we obtain a structure which helps us to understand the system from logical view

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Capture,clarify

& validate use cases

Analysis Design &

Implementation

Implement

use cases

Use cases make up the glue

Test

Verify that use cases

are satisfied

What is System Boundary?

It is shown as a rectangle.

It helps to identify what is external verses internal, and what the

responsibilities of the system are.

The external environment is represented only by actors.

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What is Relationship?

Relationship between use case and actor.

Communicates

Relationship between two use cases

Extends

Include

Notation used to show the relationships:

<< >>

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Relationship between use case and actor is often referred as

“communicates” .

Relationship between two use cases is refereed as either include or

extends.

EXTENDS:

It is used to show optional behavior, which is required only

under certain condition.

INCLUDE:

It is used to show mandatory behavior, which is required

under every condition.

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Example:

Use Case Diagram

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To understand and capture the detailed specification of a system to be developed, from user perspective.

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Completion of first version of use case diagram initiates the processes of analysis and design.

UML provides the framework to carry out the process of analysis and design in form of set of diagrams.

Every diagram and notation used in the diagram carries the semantics.

First step towards analysis and design is to specify the flow of events.

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A flow of events document is created for each use case.

Details about what the system must provide to the actor when the use is executed.

Typical contents ◦ How the use case starts and ends ◦ Normal flow of events ◦ Alternate flow of events ◦ Exceptional flow of events

Typical Course of Events has:

Actor Action (AA)

System Response (SR)

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For withdrawal of cash:

1.(SR) The ATM asks the user to insert a card.

2.(AA) The user inserts a cash card.

3.(SR) The ATM accepts the card and reads its serial number.

4.(SR) The ATM requests the password.

5.(AA) The user enters 1234.

6.(SR) The ATM verifies the serial number and password with the bank and gets the notification accordingly.

7.(SA)The ATM asks the user to select the kind of transaction.

8.(AA)User selects the withdrawal.

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Contd...

9.(SR)The ATM asks for the amount of cash; user enters Rs. 2500/-

10.(SR)The ATM verifies that the amount of cash is within predefined policy limits and asks the bank, to process the transaction which eventually confirms success and returns the new account balance.

11.(SR) The ATM dispenses cash and asks the user to take it.

12.(AA) The user takes the cash.

13.(SR) The ATM asks whether the user wants to continue.

14.(AA) The user indicates no.

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Contd...

15.(SR) The ATM prints a receipt, ejects the card and asks the user to take them

16.(AA) The user takes the receipt and the card.

17.(SR) The ATM asks a user to insert a card.

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For withdrawal of cash use case:

9. The ATM asks for the amount of cash; the user has change of mind and hits the “cancel”.

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For withdrawal of cash use case:

3 Suspicious pattern of usage on the card.

10 The machine is out of cash.

11 Money gets stuck in the machine.

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It helps in understanding the functionality of a system to be developed.

Flow of events helps in finding objects of the system to be developed.

Happens to be most important and very first step towards analysis and design.

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The functionality of the use case is captured in flow of the

events.

A scenarios is one path through the flow of events for the use

case.

Scenarios are developed to help identify objects, classes and

object interactions for that use case.

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Example:

0 Level DFD

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Example:

Level 1 DFD

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Example: Level 2 DFD

To understand the flow of each functionality and find out the objects and methods required to build the system.

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The use case diagram presents an outside view of the system

Interaction diagrams describe how use cases are realized as interactions among societies of objects.

Two types of interaction diagrams

◦ Sequence diagrams

◦ Collaboration diagrams

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Interaction diagrams are models that describe how groups of objects collaborate in some behavior

There are 2 kinds of interaction diagrams

• Sequence diagram

• Collaboration diagram

Sequence diagrams are a temporal representation of objects and their interactions

Collaboration diagrams are spatial representation of objects, links and interrelations

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Typically these diagrams capture behaviors of the single scenario.

Shows object interaction arranged in time sequence.

They show sequence of messages among the objects.

It has two dimensions, vertical represents time & horizontal

represents objects.

Components of sequence diagram:

-objects

-object lifeline

-Message

-pre/post conditions.

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Object are represented by rectangles and name of the objects are

underlined.

Object life line are denoted as dashed lines. They are used to

model the existence of objects over time.

Name:Class

They are used to model the content of communication between objects. They are used to convey information between objects and enable objects to request services of other objects.

The message instance has a sender, receiver, and possibly other information according to the characteristics of the request.

Messages are denoted as labeled horizontal arrows between life lines.

The sender will send the message and receiver will receive the message.

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Contd…

May have square brackets containing a guard conditions. This is a Boolean condition that must be satisfied to enable the message to be sent.

May have an asterisk followed by square brackets containing an iteration specification. This specifies the number of times the message is sent.

May have return list consisting of a comma -separated list of names that designate the values of returned by the operation.

Must have a name or identifier string that represents the message.

May have parentheses containing an argument list consisting of a comma separated list of actual parameters passed to a method.

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:Customer :ATM :Bank

Request password

Verify account Enter the password

Account o.k. Request option

Enter option

Request amount

Enter the amount Update transaction

Transaction commit

Insert card

Dispense cash

Request take cash

Take cash

Request continuation

Terminate

Print receipt ,eject card

Request take card

Take card

Display main screen and prompt for the card.

:Transaction

Create

Transaction

Transaction

complete

Sequence diagram [for withdrawal of cash, normal flow]

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Example:

Sequence Diagram

Collaboration diagrams illustrate the interaction between the objects, using static structure.

Unlike sequence diagram the time is not explicitly represented in these diagrams

In collaboration diagram the sequence of messages is indicated by numbering the messages. The UML uses the decimal numbering scheme.

In these diagrams, an actor can be displayed in order to represent the triggering of interaction by an element external to the system.

This helps in representing the interaction, without going into the details of user interface.

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Named objects

Links: Links are represented by a continuous line between objects, and indicates the exchange of messages.

Messages has following attributes: Synchronization --thread name, step within thread.

Sequence number

Message labels : The name of the message often corresponds to an operation defined in the class of the object that is the destination of the message. Message names may have the arguments and return values.

*[iteration].

It uses decimal notation.

Message direction.

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Object names identify which objects are participating and the links show which objects collaborate

A link between two objects must exist for one object to send message to another and vice a versa.

Messages in the collaboration diagram get transformed to more detailed signature.

They use the decimal notation system for numbering the messages.

The direction of the message defines the sender and receiver of the message

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Predecessor

Role names

Message qualifiers ◦ Iteration expression

◦ Parameters

◦ Return values

◦ Message stereotypes

Concurrent thread sequencing

Thread dependencies

Message expression

[Pre] A1:*(expression):doIt(p,r):return value

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4:Display(x,y) Simple

message

3.3.1:Display(x,y) Nested

message

4.2:subtract[Today,Birthday]:age Nested

message with

return value

[Age >=18] 6.2:Vote() Conditional

message

4.a,b.6/c.1:Turnon(Lamp) Synchro. with

other flow of

execution

1*:wash() Iteration

3.a,3.b/4*||[i:=1..n]:Turnoff() Parallel

iteration

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1. Insert card

Enter password, Enter kind

Enter amount,

Take cash, Take card

cancel,Terminate, Continue

Display main screen

unreadable card message,

request password,

request kind, request amount,

canceled message, eject card, failure message,

dispense cash, request take cash

request continuation,

print receipt, request take card

bad account message,

bad bank account message Verify account,

process transaction

Transaction succeed

Transaction failed

account o.k.

bad account,

bad password,

bad bank code

Create Transaction

Transaction complete CUST-

OMER

BANK

ATM TRANSA-

CTION

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Example:

Collaboration Diagram

To know the interaction among the objects in temporal and spatial form.

To know how objects collaborate among each other and hence delegate the responsibility to the respective objects.

To understand how the messages get matured with more information.

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A class diagram shows the existence of classes and their relationships in the logical view of a system

UML modeling elements in class diagrams are: ◦ Classes, their structure and behavior. ◦ relationships components among the classes like

association, aggregation, composition, dependency and inheritance

◦ Multiplicity and navigation indicators ◦ Role names or labels.

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Association

Aggregation

Composition

Inheritance

Dependency

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These are the most general type of relationship:

It denotes a semantic connection between two classes

It shows BI directional connection between two classes

It is a weak coupling as associated classes remain somewhat

independent of each other

Example:

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CUSTOMER ATM system

This is a special type of association

The association with label “contains” or “is part of” is an aggregation

It represents “has a “ relationship

It is used when one object logically or physically contains other

The container is called as aggregate

It has a diamond at its end

The components of aggregate can be shared with others

It expresses a whole - part relationships

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Example:

Customer ATM card

This is a strong form of aggregation

It expresses the stronger coupling between the classes

The owner is explicitly responsible for creation and deletion of the

part

Any deletion of whole is considered to cascade its part

The aggregate has a filled diamond at its end

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Window Client Area

The inheritance relationship helps in managing the complexity by ordering objects within trees of classes with increasing levels of abstraction. Notation used is solid line with arrowhead,shown below.

Generalization and specialization are points of view that are based on inheritance hierarchies.

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Account

SavingAccount CurrentAccount

Dependency is semantic connection between dependent and

independent model elements.

This association is unidirectional and is shown with dotted

arrowhead line.

In the following example it shows the dependency relationship

between client and server.

The client avails services provided by server so it should have

semantic knowledge of server.

The server need not know about client.

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Client Server

Definition: Number of instances of each class involved in the dialogue is specified by cardinality.

Common multiplicity values:

Symbol Meaning

1 One and only one

0..1 Zero or one

M…N From M to N (natural integer)

0..* From zero to any positive integer

1..* From one to any positive integer

Also thought can be given about navigability to every applicable relationship.

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In collaboration diagram we have shown the objects, their interaction and detailed message signature.

This information is carried forward to the class diagram.

At this point,we group the similar objects and form classes.

Messages get mapped to responsibilities for respective classes.

Find the attributes for every class.

Transform the links to appropriate relationships.

Relationship is further refined with respect to multiplicity and navigability.

This complete procedure brings the minimal class diagram [for

withdraw cash use case, normal flow.]

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Customer

Transaction

1

0..*

1

0..*

ATMSystem

1..*

1..*

1..*

1..*

Bank[Branch] 1

1..*

1

1..* 1

1 1

1

Till this slide we have worked out the essentials of class diagram for withdrawal of cash use case, normal flow of events.

Similar exercise required to be carried out for every scenario and clubbed all in the class diagram.

At this point, we refine this integrated class diagram to add further fine details. Approximate sketch for this class diagram has been shown at the end of this module.

Refinement attributes should be updated right from sequence diagram to class diagram.

Next few slides will take into the discussion of refinement attributes.

This process of iterative and incremental development will continue till there is no change in two consecutive iteration.

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Identify objects

Identify Messages

Group Objects

into classes

Identify & classify

Class relationships Identify class

behavior

Group classes

into domains

Validate Classes

& Objects

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Example:

Class

Diagram

Learn to build the architecture, which contains the entire information of the system to be developed.

It is this architecture which is called as BLUE PRINT is handed over for coding.

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A state transition diagram shows the states of a single object, the events or the messages that cause a transition from one state to another and the action that result from a state change.

A state transition diagram will not be created for every class in the system.

Components of State Diagram:

◦ Start State

◦ Stop state

◦ State Transition

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State: A state is a condition during the life of an object when it satisfies some condition, performs some action, or waits for an event.

The UML notation for a state is a rectangle with rounded corners.

Special states: There are two special states.

Start state: Each state diagram must have one and only one start state. Notation for start state is “filled solid circle”.

Stop State: An object can have multiple stop states. Notation for stop state is bull’s eye.

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Contd...

State transition: A state transition represents a change from an originating to a successor state.

Transition label: event name[guard condition] / action

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Example:

State Chart Diagram

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Example:

State Chart Diagram

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Example:

State Chart Diagram

A state diagram will not be created for every class.

state diagrams are used only for those classes that exhibit interesting behavior.

State diagrams are also useful to investigate the behavior of user interface and control classes.

State diagram are used to show dynamics of a individual class

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It is a special kind of state diagram and is worked out at use case level.

These are mainly targeted towards representing internal behavior of a a use case.

These may be thought as a kind of flowchart.

Flowcharts are normally limited to sequential process; activity diagrams can handle parallel process.

Activity diagrams are recommended in the following situations:

Analyzing use case

Dealing with multithreaded application

Understanding workflow across many use cases.

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Consistency checking is the process of ensuring that information in both static view of the system(class diagram) and the dynamic view of the system(sequence and collaboration diagram) is telling the same story.

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Example:

Activity Diagram

Understand the dynamic behavior of a class

Way to find the parallel processes at use case level.

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COMPONENT DIAGRAM:

Component diagrams illustrate the organizations and dependencies among software components.

A component may be

A source code component

A run time components

An executable component

Dependency relationship.

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policy.dll

Branch Bank.dll customer.dll

ATM.exe

Branch Bank.exe

Bank Server.exe

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Example:

Component

Diagram

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Example:

Modeling

A deployment diagram shows the relationship among software and hardware components in the delivered system.

These diagram include nodes and connections between nodes.

Each node in deployment diagram represents some kind of computational unit, in most cases a piece of hardware.

Connection among nodes show the communication path over which the system will interact.

The connections may represent direct hardware coupling line RS-232 cable, Ethernet connection, they also may represent indirect coupling such as satellite to ground communication.

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ATM_ machine

Bank_ server

Branch Bank_

Ethernet Ethernet

Bank.exe

BankServer.exe ATM.exe

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Example:

Deployment Diagram

To understand the organization of software modules and their deployment on the respective hardware.

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It may be:

1.Calendar Centric

2.Requirement Centric

3.Documentation Centric

4.Quality Centric

5.Architecture Centric

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Architecture driven projects represent the most mature style of development.

These projects are characterized by a focus on creating a frame work that satisfies all known requirement, yet is resilient enough to adapt to those requirements, that are not yet known or well understood.

In every sense of the word, architect-driven policies are in evolutionary step beyond requirement driven policies.

Architecture driven style of development is usually the best approach for the creation of most complex software intensive systems

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Architecture driven style of development typically observe the following process:

1. Specify the system’s desired behavior through a collection of scenarios. (Analysis)

2. Create, then validate, an architecture. (Design)

3. Evolve that architecture, making mid-course corrections as necessary to adopt to new requirements as they are uncovered.

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What exactly is nature of the well structured object

oriented architecture??

1. A set of classes, typically organized into multiple hierarchies.

2. A set of collaboration that specify how those classes co-operate to provide various system function.

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Use case driven

Architecture centric

Incremental and iterative approach.

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