Introduction Use Case Diagram

Unified Modeling Language (UML) Introduction and Use Case Diagram

Miaoqing Huang University of Arkansas Spring 2011

1 / 24 Introduction Use Case Diagram Outline

1 Introduction

2 Use Case Diagram

2 / 24 Introduction Use Case Diagram Outline

1 Introduction

2 Use Case Diagram

3 / 24 Introduction Use Case Diagram What is UML?

UML is a modeling language A model is an abstraction describing a system Modeling language is used to express design Use notation for depicting models UML is the de facto modeling language in software engineering Created and managed by the Object Management Group, now at version 2.3 (May 2010) Key persons: (three amigos) James Rumbaugh, Grady Booch, Ivar Jacobson UML includes a set of graphical notation techniques to create visual models of software-intensive systems 14 diagrams 7 structural diagrams 7 behavior diagrams

4 / 24 Introduction Use Case Diagram UML Diagrams

5 / 24 Introduction Use Case Diagram UML Diagrams – Example

use case diagram class diagram sequence diagram

6 / 24 Introduction Use Case Diagram UML Diagrams – Example Use case diagram Describe the functional behavior of the system as seen by the user Class diagram Describe the static structure of the system: Objects, attributes, associations Sequence diagram Describe the dynamic behavior between objects of the system State machine diagram Describe the dynamic behavior of an individual object

7 / 24 Introduction Use Case Diagram UML Core Conventions All UML Diagrams denote graphs of nodes and edges Nodes are entities and drawn as rectangles or ovals Rectangles denote classes or instances Ovals denote functions Names of Classes are not underlined SimpleWatch Firefighter Names of Instances are underlined myWatch:SimpleWatch Joe:Firefighter An edge between two nodes denotes a relationship between the corresponding entities

8 / 24 Introduction Use Case Diagram Use Case Diagram Use case diagrams represent the functionality of the system from user’s point of view

Use case

Actor ReadTime

SetTime WatchUser WatchRepairPerson

ChangeBattery

9 / 24 Introduction Use Case Diagram Class Diagram Class diagrams represent the structure of the system

Association Class

Multiplicity Watch 1 1 1 1 2 1 2 1 PushButton state LCDDisplay Battery Time push() blinkIdx Load Now release() blinkSeconds() blinkMinutes() blinkHours() stopBlinking() Operations Attribute referesh()

10 / 24 Introduction Use Case Diagram Sequence Diagram Sequence diagrams represent the behavior of a system as messages (“interactions”) between different objects Actor Message Object Lifeline

:WatchUser :Watch :LCDDisplay :Time

pressButton1() blinkHours() pressButton1() blinkMinutes() pressButton2() incrementMinutes() refresh() pressButton1and2() commitNewTime() stopBlinking() Activation

11 / 24 Introduction Use Case Diagram State Machine Diagram State machine diagrams represents behavior of a single object with interesting dynamic behavior

Event Initial state button2Pressed button1&2Pressed Blink Increment Hours Hours

Transition button1Pressed

button2Pressed button1&2Pressed Blink Increment Minutes Minutes State

button1Pressed

button2Pressed Stop Blink Increment Blinking Seconds Seconds Final state

12 / 24 Introduction Use Case Diagram Outline

1 Introduction

2 Use Case Diagram

13 / 24 Introduction Use Case Diagram What is a use case?

Scenario A sequence of steps describing an interaction between a user and a system The customer browse the catalog and adds desired items to the shopping basket. When the customer wishes to pay, the customer describes the shipping and credit information and confirms the sale. The system checks the authorization on the credit card and confirms the sale both immediately and with a follow-up email. Use case A use case is a set of scenarios tied together by a common user goal Buy a Product use case: a successful purchase or authorization failure

14 / 24 Introduction Use Case Diagram Describe a use case

A set of scenarios in the Use Case “Buy a product online”: 1. Customer browses through catalog and selects items to buy 2. Customer goes to check out 3. Customer fills in shipping information 4. System presents full pricing information, including shipping 5. Customer fills in credit card information 6. System authorizes purchase 7. System confirms sale immediately 8. System sends confirming email to customer

15 / 24 Introduction Use Case Diagram An Example

uc Use Cases System Boundary

receive order Order <> Order Food Wine Waiter confirm order place order

Serve Cook Food Food Chef <> {if wine was ordered}

Serve Wine

Eat <> Drink Food {if wine Wine Client was served} facilitate payment

pay <> accept Pay for {if wine Pay for payment Food was Wine Cashier consumed}

16 / 24 Introduction Use Case Diagram Actor and Use Case An actor is a role that a user play with respect to the system Actors are connected to the use cases by a line A single actor may perform many use cases A use case may have several actors performing it

Four types of relationships in use case diagram Generalization between use cases Generalization between actors Include relationship between use cases Extend relationship between use cases

17 / 24 Introduction Use Case Diagram Generalization between use cases

Different versions of a use case share some actions in common and have some that are unique to each one Generalized use case: abstract use case It may never exist in a real system Specialized use case: concrete use case

Pay utility bill

18 / 24 Introduction Use Case Diagram Generalization between Actors

Specialized actor can do everything the general actor can do, and more

19 / 24 Introduction Use Case Diagram Generalization between Actors

Specialized actor can do everything the general actor can do, and more

20 / 24 Introduction Use Case Diagram Generalization between Actors

Specialized actor can do everything the general actor can do, and more

21 / 24 Introduction Use Case Diagram Include Relationship between Use Cases

One use case includes the functionality of another use case Invocation of one use case by another one e.g., calling a function or invoking an operation within source code

22 / 24 Introduction Use Case Diagram Extend Relationship between Use Cases

One use case may be extended by the functionality in another use case

23 / 24 Introduction Use Case Diagram Include, Generalization, Extend

Include Use include when you are repeating yourself in two or more separate use cases and you want to avoid repetition Generalization Use Generalization when you are describing a variation on normal behavior and you wish to describe it casually Extend Use extend when you are describing a variation on normal behavior and you wish to use the more controlled form, declaring your extension points in your base use case

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