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Requirements Tell a Story

Explore the importance of use cases in system design through narrative, scenario, and conversation forms. Learn how to identify actors, write glossaries, and improve use case definitions effectively.

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Requirements Tell a Story

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  1. Requirements Tell a Story

  2. Use Case

  3. Function and Form

  4. Narrative Form

  5. First Form: A NarrativeMake a Payment

  6. Scenario Form

  7. Second Form: A ScenarioRegister Customer With Automatic Activation

  8. Conversation Form

  9. Third Form: A ConversationMake A Payment - General Flow

  10. Comparing the Three Forms

  11. The Benefits of Use Cases

  12. Use Cases Aid Understanding

  13. Use Cases Vary by AbstractionLevel

  14. Use Cases Vary in Scope

  15. Use Cases Vary in Detail

  16. What Use Cases Cannot Do

  17. Finding Use Cases

  18. Finding Use Cases

  19. Naming Use Cases

  20. Primary and Secondary Actors

  21. Group individuals according to their common use of the system. Identify the roles they take on when they use or are used by the system Each role is a potential actor Name each role and define its distinguishing characteristics. Add these definitions to your glossary Don’t waste time debating actor names Naming Actors

  22. Actor and Use Case Checklist

  23. Glossary

  24. Glossaries

  25. Build Consensus

  26. Identify a concept and its distinguishing characteristics More than a synonym for a word Identifies a way of mentally dividing reality for purpose of talking or thinking Defining Concepts

  27. Why this concept is important Typical sizes or values Clarify likely misunderstandings Show an example Explain graphical symbols Relate entries Writing Glossary Entries

  28. A Good Form for Definitions

  29. Improving Glossary Definitions

  30. Relating Definitions

  31. Define Acronyms and Their Concepts

  32. Avoid Using“Is When” or “Is Where”

  33. Explain What Is Unclear

  34. Level—summary, user, or system (internal) use case? Actor(s)—role names of people, objects or external systems initiating this use case Context—the current state of the system and actor Preconditions—what must be true before a use case can begin Setting the Stage for the Use Case

  35. Variations— different ways to accomplish use case steps Exceptions— errors that occur during the execution of a step Policies— specific rules that must be enforced by the use case Issues— questions about the use case Design notes— hints to implementers Post-conditions— what must be true about the system after a use case completes Other requirements— what constraints must this use case conform to Priority— how important is this use case? Frequency— how often is this performed? Completing The Picture

  36. Make Clear What You Don’t Know

  37. Avoid Vague Words

  38. Write General and Specific Cases

  39. Actor Actions

  40. Include System Actions

  41. Describing Actions

  42. Condense Information Entryand/or Validation Actions

  43. State System Actions at aReasonably High Level for Users

  44. Showing Optional and Repeated Actions

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