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System Analysis and Design Using UML

INSTRUCTOR:Jesmin Akhter

Lecturer, IIT, JU

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What is UML?

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.

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UML refers to:

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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UML diagrams:

1. Use case diagram2. Class Diagram3. Behavioral diagrams

- State chart diagrams- Object diagram

- Activity diagrams- Interaction diagrams

- Sequence diagrams- Collaboration diagrams

4. Implementation diagrams- Component diagram- Deployment diagram

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Semantics of Diagrams:

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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Semantics of Diagrams:

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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What is USE CASE diagram?

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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ACTOR:

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.

Customer Manager Cashier

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ACTOR:

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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ACTOR:

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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ACTOR:

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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ACTOR:

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 of application

domain and must be used. Other system: The other system with which the system must

interact.

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USE CASE:

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:

Open new account Withdrawal of cash from ATM

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USE CASE:

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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USE CASE:

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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SYSTEM BOUNDARY:

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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RELATIONSHIP

What is Relationship?

Relationship between use case and actor.

Communicates Relationship between two use cases

Extends

Uses Notation used to show the relationships:

<< >>

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RELATIONSHIP:

Relationship between use case and actor is often referred as “communicates” .

Relationship between two use cases is refereed as either uses or extends.

USES: - Multiple use cases share a piece of same functionality. - This functionality is placed in a separate use case rather than

documenting in every use case that needs it.

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RELATIONSHIP:

Contd... A uses relationship shows behavior that is common to one or

more use cases.

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

under certain condition.

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USE CASE diagram:

Use case diagram for the shown functionality.

Balance status report

Withdraw cash

Validation

uses

CustomerClerk

Manager

extends

ATM

Use case diagram for ATM

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Transfer fund

View balance

Transfer funds

Deposit fundsCustomer

Withdraw money

Bank officer

Change pin

Make payment Client