Use Case

Use Case is a typical sequence of actions that an actor performs to complete a specific task

How to write use case ?

• Name
• Actors
• Goal
• Preconditions
• Summary
• Steps
• Post conditions

Use case for check out an item for borrower

• Name - Check out a book
• Actor - Checkout Clerk
• Goal - To successfully lend the book to the borrower
• Preconditions - The borrower must have a valid card
• Steps

Actors Actions - Scan the bar-code of the book - Check the the card of borrower - Confirmation

System Actions

• Display that the loan is allowed
• Confirm the loan

Post conditions - The system has the record corresponding the book that has been lend

Extension

Model optional / exceptional behaviour

Inclusion

To extract common steps that are shared by multiple classes