Use Case Analysis PDF

Chapter 4 Use Case Analysis Dr. Naglaa Abdelhady Sleem Information Systems Department Faculty of Computers and Information Assiut University Learning Objectives Explain the purpose of use cases in the analysis phase of the SDLC. Describe the various parts...

Chapter 4 Use Case Analysis Dr. Naglaa Abdelhady Sleem Information Systems Department Faculty of Computers and Information Assiut University Learning Objectives Explain the purpose of use cases in the analysis phase of the SDLC. Describe the various parts of a use case and the purpose of each part. Describe how use cases contribute to the functional requirements. Describe how use cases inform the development of test plans. Explain the process used to create a use case. Copyright ©2019 John Wiley & Sons, Inc. 2 What is a Use Case? UNDERSTANDING THE PURPOSE OF THIS TOOL Copyright ©2019 John Wiley & Sons, Inc. 3 Use Cases A use case represents how a system interacts with its environment by illustrating the activities that are performed by the users and the system’s responses. Use cases express and clarify user requirements. Purpose - define the expected interaction between the user and the system. Use that interaction to more fully describe functional requirements Used extensively in the analysis phase. Often a part of user interviews or JAD sessions. Copyright ©2019 John Wiley & Sons, Inc. 4 Use Cases Techniques Visual Modeling Use case diagram: typically used in conjunction with the textual use case. Textual Document Templates Copyright ©2019 John Wiley & Sons, Inc. 5 Use Case Diagram A use case diagram is used to graphically depict a subset of the use case model to simplify communications. Much of the use case model is in fact textual, with the text captured in the use case specifications that are associated with each use case model element. These specifications describe the flow of events of the use case. Copyright ©2019 John Wiley & Sons, Inc. 6 Syntax for Use-Case Diagram Slide 7 Extend and Include Relationships Slide 8 The Use-Case Diagram for Appointment System Slide 9 Use-Case Diagram with Specialized Actor Slide 10 Use Case Styles ELEMENTS AND FORMATS Copyright ©2019 John Wiley & Sons, Inc. 11 Obtain Shop Manager Approval Use Case 12 Elements of a Use Case Each use case has a name and number, and brief description. The priority may be assigned to indicate the relative significance. The actor refers to a person, another system, or a hardware device that interacts with the system to achieve a useful goal. The trigger for the use case – the event that causes the use case to begin. Events triggers can be external or temporal Copyright ©2019 John Wiley & Sons, Inc. 13 Use Case Basic Information From Figure 4-1 Casual Format Use Case Copyright ©2019 John Wiley & Sons, Inc. 14 Normal Course The major steps that are performed to execute the response to the event Normal Course: 1.0 Order a customized drone 1. The customer selects a base model drone from a list of models 2. The system provides availability status for that model (in stock, out of stock) 3. For out of stock status, system displays expected date available a. Customer accepts future availability date; proceed to step 4 b. Customer rejects future availability date; return to step 1 4. The system displays a list of options and upgrades for the selected model 5. The customer selects desired model options and upgrades 6. Preliminary order with cost estimate is created and displayed 7. Customer may return to step 4, confirm order, save for future consideration, or exit without saving 8. Unconfirmed orders are stored in Unconfirmed Custom Order datastore 9. Confirmed orders are saved in Confirmed Custom Order datastore 10. Shop manager is notified of Confirmed Order requiring approval Copyright ©2019 John Wiley & Sons, Inc. 15 Use Cases in Sequence Uses cases often performed in sequence. No single use case should be too large. Important to define initial and ending states. Copyright ©2019 John Wiley & Sons, Inc. 16 Preconditions and Postconditions Preconditions define what must be complete before beginning this use case. Postconditions define what is complete when this use case ends. Preconditions: 1. The customer is authenticated by logging in to his account 2. The Sales System Order Processing application is online Postconditions: 1. Unconfirmed order is stored in Unconfirmed Custom Order datastore 2. Confirmed order is stored in Confirmed Custom Order datastore 3. Shop manager sent notice of Confirmed Order requiring approval Copyright ©2019 John Wiley & Sons, Inc. 17 Fully-Dressed Use Case Format (1 of 2) Very thorough, detailed, and highly structured. Adds new sections, including, Alternative courses Inputs and outputs for steps Summary inputs and outputs. See Figure 4-3 for example Copyright ©2019 John Wiley & Sons, Inc. 18 Copyright ©2019 John Wiley & Sons, Inc. 19 Fully-Dressed Use Case Format (2 of 2) Use this format when: Users are not closely engaged with development team Project has high complexity and high risk Test cases need to be fully described Remote collaborating teams need detailed, shared understanding of user needs. Copyright ©2019 John Wiley & Sons, Inc. 20 Use Case Practical Tips Use gradual refinement. Concentrate on describing the user’s objectives with the system completely and accurately. Keep both audiences in mind – users and developers. Create use cases only when needed to clarify what the system must do from the user’s perspective. Not needed for simple events. Copyright ©2019 John Wiley & Sons, Inc. 21 Creating Use Cases Identify events the system must respond to – develop Event-Response List Create use case form for the complex events For each use case: Identify the major steps Identify elements with each major step (inputs and outputs) Confirm use case with users through role-playing Revise functional requirements as needed Copyright ©2019 John Wiley & Sons, Inc. 22 Creating Use Cases Identify the major use cases Identify the major steps within each use case Identify elements within steps Confirm the use case Copyright ©2019 John Wiley & Sons, Inc. 23 Step 1: Identify the Use Cases Copyright ©2019 John Wiley & Sons, Inc. 24 Step 2: Identify the Major Steps within each Use Cases 25 Step 3: Identify Elements within Steps Copyright ©2019 John Wiley & Sons, Inc. 26 Step 4: Confirm the Use Case Copyright ©2019 John Wiley & Sons, Inc. 27