Use Case Modeling
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Use Case Modeling
Use Case Modeling
Use case diagram For each use case we develop
Object class diagram (with attributes only)System sequence diagram (analysis)Detailed sequence diagram (design)Updated object class diagram [with both
attributes and programs (methods)] Then put together object class diagrams for all use
cases and have one such diagram for entire system
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What is Use Case Modeling?
use case model: a view of a system that emphasizes the behavior as it appears to outside users. A use case model partitions system functionality into transactions (‘use cases’) that are meaningful to users (‘actors’).
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Use Case Modeling: Core Elements
Construct Description Syntax
use case A sequence of actions, including variants, that a system (or other entity) can perform, interacting with actors of the system.
actor A coherent set of roles that users of use cases play when interacting with these use cases.
system boundary
Represents the boundary between the physical system and the actors who interact with the physical system.
UseCaseNam e
ActorNam e
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Construct Description Syntax
association The participation of an actor in a use case. i.e., instance of an actor and instances of a use case communicate with each other.
generalization A taxonomic relationship between a more general use case and a more specific use case.
extend A relationship from an extension use case to a base use case, specifying how the behavior for the extension use case can be inserted into the behavior defined for the base use case.
Use Case Modeling: Core Relationships
<<extend>>
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Construct Description Syntax
include An relationship from a base use caseto an inclusion use case, specifyinghow the behavior for the inclusion usecase is inserted into the behaviordefined for the base use case.
Use Case Modeling: Core Relationships (cont’d)
<<include>>
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Use cases help…
· Capture the system's functional requirements from the users' perspective
· Actively involve users in the requirements-gathering process
· Provide the basis for identifying major classes and their relationships
· Serve as the foundation for developing system test cases
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Use Case Diagrams
Actor Line: actor communicates with or is associated
with use-case
Use Case Modeling (cont’d)
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Use Case relationships: <<uses>>: one use case always involves the
steps of another <<extends>>: under certain conditions, a use case
follows a variant
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Goals of Use Cases Interactions that provide value to actors No implementation specific language
No assumptions about how the use case may be realized in code or user-interface
Note: use-cases drive the whole life-cycle, and they get refined – implementation specific use-cases
User-appropriate level of detail General at requirements gathering stage
User-appropriate volume Large systems: no more than 70-80 use cases Small number of use cases – forces abstraction
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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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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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OOAD --- USE CASE driven
Capture,clarify& validate use cases
Analysis Design &Implementation
Implement use cases
Use cases make up the glue
Test
Verify that use casesare satisfied
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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
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Flow of Events: 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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Normal Flow of Events:
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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Normal Flow of Events:
Contd... 9.(SR)The ATM asks for the amount of cash; user enters $(s). 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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Normal Flow of Events:
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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Alternative Flow of Events:
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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Exceptional Flow of Events:
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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:Customer :ATM :BankRequest password
Verify accountEnter the password
Account o.k.Request option
Enter option
Request amount
Enter the amountUpdate transactionTransaction commit
Insert card
Dispense cashRequest take cash
Take cashRequest continuation
TerminatePrint receipt ,eject card
Request take cardTake card
Display main screen and prompt for the card.
:TransactionCreate Transaction
Transaction complete
Sequence Diagram [for withdrawal of cash, normal flow]
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Collaboration Diagram [for withdrawal of cash, normal flow]
1. Insert cardEnter password, Enter kindEnter amount,Take cash, Take cardcancel,Terminate, Continue
Display main screen unreadable card message,request password,request kind, request amount,canceled message, eject card, failure message,dispense cash, request take cashrequest continuation,print receipt, request take cardbad account message,bad bank account message
Verify account,process transaction
Transaction succeedTransaction failedaccount o.k.bad account,bad password,bad bank code
Create TransactionTransaction complete
CUSTOMER
BANK
ATM TRANSACTION
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Class Diagram [for withdrawal of cash, normal flow]
Customer
Transaction
1
0..*
1
0..*
ATMSystem
1..*
1..*
1..*
1..*
Bank[Branch]
1
1..*
1
1..*1
1
1
1
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Component Diagram [for withdrawal of cash]
policy.dll
Branch
Bank.dllcustomer.dll
ATM.exe
Branch
Bank.exe
Bank
Server.exe
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