Use Cases Use Case Diagrams Chapter 3 1

Use Cases & Use Case Diagrams Chapter 3 1

Outline v Use Case – defined v Techniques for Identifying Use Cases § User Goal § Event Decomposition v UML's Use Case Diagram 2

Use Case - Defined v Use case - an activity that the system performs § usually in response to a request by a user § Functional Requirements § Verb + Noun – Place order – Issue complaint v Techniques to Identify use cases: § User Goal § Event Decomposition 3

Identifying Use Cases- User Goal Technique v Ask the users what they need the system to do • Identify the users • Interview them • Create the list of use cases § Some users may need the same use case § Watch out for duplicates, inconsistencies • Verify the list with the users 4

Identifying Use Cases- Event Decomposition v Identify the events that occur to which the system must respond. § Event - an occurrence at a specific time & place which needs to be remembered § Use Case - what the system does when the event occurs § Prior Conditions & Events 5

Identifying Use Cases- Event Decomposition v Types of Events § External § Temporal § State 6

UML's Use Case Diagram 7

UML - The Unified Modeling Language v Developed by the "3 Amigos" - James Rumbaugh, Grady Booch, & Ivar Jacobson • UML – an OO modeling language consisting of multiple types of diagrams • Rational Unified Process (RUP) - an object-oriented systems development methodology • Rational Software, which is now owned by IBM v UML was adopted & now managed by OMG (Object Management Group) v UML Diagrams: § Structure diagrams - Class diagram, Component diagram, Deployment diagram, Object diagram, Package diagram, etc. § Behavior diagrams - Activity diagram , Use Case diagram, Sequence diagram, State machine, Communication diagram, etc. 8

Use Case Diagram v A UML diagram depicting the relationship between actors & use cases § Use Case - an activity that the system performs § Defines Scope/Functional Requirements v Symbols § Automation Boundary - The boundary between the software and the actors of the system § Actor - Anyone or thing that interacts with the system § Association - depicts a usage relationship between an actor and a use case • <<includes>> association - Used when one use case (base) includes another use case (the inclusion use case)<<includes>> <<extends>> <<uses>> Customer Billing <<system>> Time 9

Use Case Diagram - Example • Prefer "Place an order" 10

Use Case Diagram - Practice ATM System Withdraw cash Customer 11

Use Case Diagram – Multiple Actors Create new order Lookup item Customer availability Lookup backorders Sales clerk Update order 12

Use Case Diagram - Example Create new order <<includes>> Lookup item Customer availability <<includes>> Validate customer account Sales clerk <<includes>> Update order Reuse! 13

"Withdraw Cash” Use Case – i. e. scenario Withdraw cash Customer ATM Bank 14