Systems Analysis Use Case Modeling OOD_ch06.ppt
- 1. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 1 Use-Case Modeling Chapter 6
- 2. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 2 Key Ideas A use case illustrates the activities that are performed by users of a system. Use cases are logical models -- they describe the activities of a system without specifying how the activities are implemented.
- 3. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 3 USE-CASE DESCRIPTIONS
- 4. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 4 What are Use-Case Descriptions? Describe basic functions of the system What the user can do How the system responds Use cases are building blocks for continued design activities.
- 5. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 5 How Are Use-Cases Created? Two steps: Write text-based case descriptions Translate descriptions into diagrams Describes one and only one function, but may have multiple paths. Developed working with users for content.
- 6. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 6 Types of Use-Cases Overview versus detail Essential versus real
- 7. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 7 Elements of a Use-Case Description Use Case Name: ID: Importance Level: Primary Actor: Use Case Type: Stakeholders and Interests: Brief Description: Trigger: Relationships: (Association, Include, Extend, Generalization) Normal Flow of Events: Subflows: Alternate/Exceptional Flows:
- 8. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 8 Guidelines for Creating Use-Case Descriptions Write each step in “SVDPI” form Clarify initiator and receivers of action Write from independent observer perspective Write at same level of abstraction Ensure a sensible set of steps Apply KISS principle liberally Write repeating instructions after the set of steps to be repeated.
- 9. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 9 Your Turn How would you make requirements gathering (interviews, questionnaires, observation, and document analysis) more effective by knowing that eventually you will be creating use-case descriptions and diagrams?
- 10. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 10 USE-CASE DIAGRAMS
- 11. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 11 Syntax for Use-Case Diagram
- 12. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 12 The Use-Case Diagram for Appointment System
- 13. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 13 Use-Case Diagram with Specialized Actor
- 14. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 14 Extend and Include Relationships
- 15. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 15 CREATING USE-CASE DESCRIPTIONS AND USE- CASE DIAGRAMS
- 16. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 16 Major Steps in Writing Use- Cases Identify the major use-cases Expand the major use-case Confirm the major use-cases Create the use-case diagram
- 17. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 17 Identifying the Major Use- Cases Identify the system’s boundaries List the primary actors List the goals of each primary actor Identify and write the major use- cases Carefully review use-cases
- 18. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 18 Expand the Major Use- Cases Choose one major use-case to expand Fill in details on the use-case template Fill in the steps of the normal flow of events Normalize the size of each step Describe alternate or exceptional flows Simplify and organize as necessary
- 19. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 19 Confirm the Major Use Cases Review the current set Consider semantics and syntax Helpful to involve the users Iterate the entire set of steps until all use cases are defined
- 20. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 20 Create the Use-Case Diagram Start with system boundary Place elements in order to be easy to read Place actors on the diagram Conclude by connecting actors to use cases by lines
- 21. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 21 Selecting the Appropriate Techniques Interviews JAD Questionnaires Document Observation Analysis Type of As-Is As-Is As-Is As-Is As-Is Information Improve. Improve. Improve. To-Be To-Be Depth of High High Medium Low Low Information Breadth of Low Medium High High Low Information Integration Low High Low Low Low of Info. User Medium High Low Low Low Involvement Cost Medium Low- Low Low Low- Medium Medium
- 22. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Identify the major use-cases Expand the major use-case Confirm the major use-cases Create the use-case diagram
- 23. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 23 Your Turn Create a set of use cases for campus housing. Consider the steps in registering for campus housing, in being assigned to a particular unit, to being matched with roommates, to moving in.
- 24. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 24 Summary Use-case descriptions are the basis for further analysis and design. They are created based on 7 guidelines and 13 steps. Use-case diagrams present a graphical overview of the main functionality of a system.
- 25. PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved. Slide 25 Expanding the Domain Additional resources regarding use-cases and many other object-oriented development topics can be found at: http://www.omg.org