Use cases Week 05 1. Use‐case diagram 2 – Depicts the interactions between the system and external systems and users. – Graphically describes who will.

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Use cases

Week 05

Use case diagram‐

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– Depicts the interactions between the system and external systems and users.

– Graphically describes who will use the system and in what ways the user expects to interact with the system

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Use-case diagrams and use-case model

• A use case diagram illustrates– a set of use cases for a system,– the actors of these use cases, – the relations between the actors and these use

cases – the relations among the use cases.

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A Scenario • The scenario is an ordered sequence of

interactions between the actor(s) and the system to accomplish a goal. It consists of: – Normal Flow – Alternate Flow – Sub-Flows – Exceptions

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Normal Flow

Conduct ATM Transaction

Normal Flow: 1. Customer inserts the bank card.2. Customers enters password.3. System verifies password.4. System presents a list of transaction types that the

customer may conduct.5. Customer selects a type of transaction.

Normal flow is the best-case scenario, EX:

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Sub-Flows

RegisterPatient Normal Flow: 1. The registration clerk enters or updates personal

data.

Sub Flows: 1.1 The registration clerk enters the Social Security Number of the new patient.

1.2 The registration clerk enters or updates patient’s address.

1.3 The registration clerk enters or updates patient’s phone number.

1.4 The registration clerk enters or updates the name, the address and the phone number of the patient’s closest relative.

• Sub-flows identify the details of the steps in the normal flow, EX:

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Alternate Flow and Exceptions

• Alternate steps identify remedies; exceptions signify failure, EX:

Receive Patient Alternate

Flow/ Exceptions:

3.a Patient is new. Reception clerk directs the patient to registration…3.bPatient is not new but personal or insurance data has changed. Reception clerk directs the patient to registration…3.cPatient has lost the hospital ID card. Reception clerk directs the patient to registration…

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Use cases diagram

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Use cases diagram

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The Process Modeling use cases

Step 1: Identify business actorsStep 2: Identify Business RequirementsUse CasesStep 3: Construct Use Case Model‐DiagramStep 4: Document Business RequirementsUse case Narratives‐

Major component of a Use case Diagram

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Actor

Use case

Actor to Use caseAssociation

Inheritance

Inclusion Of a Use case by Another

Extension of aUse case by Another

System Boundary

<<include>>

Notes

<<extends>>

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Use Cases: Describing Processes

Use cases• a use case describes the sequence of events of

some types of users, called actors, using some part of the system functionality to complete a process.

• Describe what a system does, not how the system does

• A series of interaction of a User with the System, which provides some concrete, measurable results to the User

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For example, to carry out the process of buying things at a store when a POST

is used_ two actors must be involved: Customer and Cashier,

_ the following sequence of events must be performed:

The Customer arrives at a checkout with items to purchase. The Cashier records the purchase items and collect payment. On

completion, the Customer leaves with the items

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use cases

1. One method to identify use case is actor-based:(a)Identify the actors related to a system or organization,

i.e. find and specify all the actors by looking at which users will use the system and which other systems must interact with it.

(b) For each actor, identifying the processes they initiate or participate in by looking at how the actor communicates/interacts with (or use) the system to do his work.

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. A second method to identify use cases is event-based.

(a) Identify the external events that a system must respond to.

(b) Relate the events to actors and use cases.

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Actor

• An actor represents a type of users of the system or external systems that the system interacts with.

• An actors may model anything that needs to interact with the system to exchange information: a human user, a computer system, an electrical or a mechanical device such as a timer.

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Who is an Actor?• The User of the system is usually the Actor

• The Actor (and not the User) is shown sending and receiving messages to and from the System

– Example: John the Branch Manager, John the Customer and John the Teller may be one and the same person

• External Devices may also be Actors– e.g. ATMs, Keypads, Printers

• External Systems may also be Actors– e.g.A Mainframe

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Finding Actors– Who provides/uses Information to/from the

System?– Who Supports this Functionality?– Which other Systems will this System Interact with? – The External Devices (Keypads, Printers etc.) that

the system will Interact withProcess Comment: Produce first cut of the list of Actors, then

Cull them after drawing Initial Use Case diagrams

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Actor: Variations• Primary Actor versus Secondary Actors:

– Primary

• The first or main Actor who uses the system

• The main Actor who benefits from the system

• e.g. Customer, Patient, Doctor– Secondary Actor:

• The Actor who derives indirect benefits from or uses the system (e.g. Branch manager); Depends on Perspective

• Direct versus indirect actors–Banking System: Teller VS Customer

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A high-level use case describe a process(Use case narrative)‐

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Relationships

associationsOn a use case diagram, associations are drawn between actors and use cases to show that an actor carries out a use case.•Modeled as a solid line connecting the actor and theuse case • May be bidirectional or unidirectional

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<<extend>>

• complex use case in order to simplify the original case and thus extend its functionality.• The extension use case extends

the functionality of the original use case.

• Shows optional behavior of a Use Case

• Depicted as an arrow headed line (either solid/dashed)

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Uses (or Include)<<include>>

• The base use case explicitly incorporates thebehavior of another use case.• The relationship between the abstract use caseand use case that uses it.Abstract use case: a use case that reduces redundancyamong two / more other use cases by combining thecommon steps found in those cases.

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Depends on

<<depends on>>• A relationship between use cases indicating

that one use case cannot be performed until another use case has been performed.

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Inheritance

• • A relationship between actors created tosimplify the drawing when an abstract actorinherits the role of multiple real actors

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Benefits

– Facilitates and encourages user involvement– Provides a tool for capturing functionalrequirements– Provides an aid in estimating project scope,effort and schedule– Provides a tool for requirements traceability– Provides a framework for driving the systemdevelopment project

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Online Shopping Portal| A case study

• A customer visits the online shopping portal. A customer may buy item or just visit the page and logout.

• The customer can select a segment, then a category, and brand to get the different products in the desired brand.

• The customer can select the product for purchasing. The process can be repeated for more items.

• Once the customer finishes selecting the product/s the cart can be viewed , If the customer wants to edit the final cart it can be done here.

• For final payment the customer has to login the portal, if the customer is visiting for the 1st time he must register with the site, else the customer must use the login page to proceed.

• Final cart is submitted for payment and card details and address(where shipment has to be made) are be confirmed by the customer .

• Customer is confirmed with a shipment Id and delivery of goods within 15 days.

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• Actors– Customer– Administrator.

• Use case (functionality)

Allows the customer to view the different categories and further to different products within the brands eg.

Allows the customer to shop online saying time and cost of customer.

The portal provides a bill and an shipment Id which can be used to track the delivery status of the goods purchased by the customer .Category:.

Customer

Customers when enter the site and view the various products in different category.

Authentication of the customer is done for the payment of the shopping done

Customer can browses through the products available in the shop, can select some of them and put into the shopping cart.

Customer can anytime change the items in the cart either by adding new items or by removing existing items. Customer proceeds towards the payment counter. Finalize product list of items he finally wish to buy and make the final payment.

Administrator

Updates the details of the different category ,segments etc

Verifies the customer card details and records the details for shipment of goods.

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Library management system• A library contains books and journals. The task is to develop a

computer system for borrowing books. To borrow a book the borrower must hold a valid library card, have no books overdue by more than one week, and have no outstanding fines. There is a limit of 6 books that can be borrowed by a student and 12 books by a staff member.

• The library may have several copies of a given book.

• It is possible to reserve a book.

• Some books are for short term loans only. Other books may be borrowed for 3 weeks. Borrowers can extend the loans.

• Give a use case description for the following use case:

Borrow a copy of a book

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CASE STUDY: Stock Maintenance.

Now a day’s people should purchase things in stores. It is the System used to maintain the product details and stock. So in this stock maintenance have the details about the product, purchase, sales and stock what are the stocks we had.  The product details contain product code, Product name, Opening Stock and Prices. These details are maintained in database.

In the purchasing function we must have the details about the store, quantity and also price.The Sales Details contain Date, Customer name, Product code, Quantity and Prices. The Stock Details contain product id, opening stock, purchase stock, current stock, and sales. The stock details are maintaining the database and view the stock between two dates

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Case Study :-RAILWAY RESERVATION SYSTEM

Railway Reservation System is a system used for booking tickets over internet. Any Customer Can book tickets for different trains.Customer can book a ticket only if the tickets are available. Customer searches for the availability of tickets then if the tickets are available he books the tickets by initially filling details in a form. Tickets can be booked in two ways by i-ticket or by e-ticket booking.

In case of i-ticket booking customer can book the tickets online and the tickets are couriered to Particular customer at their address. But in case of e-ticket booking and cancelling tickets are booked and cancelled online sitting at the home and customer himself has to take print of the ticket but in both the cases amount for tickets are deducted from customers account. 

For cancellation of ticket the customer has to go at reservation office than fill cancellation form and ask the clerk to cancel the ticket than the refund is transferred to customer account. After booking ticket the customer has to checkout by paying fare amount to clerk.

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