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Use Case Diagrams

Use Case Diagrams. Lecture Oo14 Use Cases. References. Booch, et al , The Unified modeling Language User’s Guide, AWL, 1999, Chapt 16 & 17 Fowler & Scott, UML Distilled Applying the Standard Object Modeling Language, AWL, 1997, Chapt 3. Teaching Points. What are Use Cases

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Use Case Diagrams

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  1. Use Case Diagrams Lecture Oo14 Use Cases

  2. References • Booch, et al, The Unified modeling Language User’s Guide, AWL, 1999, Chapt 16 & 17 • Fowler & Scott, UML Distilled Applying the Standard Object Modeling Language, AWL, 1997, Chapt 3

  3. Teaching Points • What are Use Cases • Use Case Diagrams • Use Case Specifications

  4. Review • What are the phases of our S/W Eng method? • What happens in each phase? • What are analysis and design?

  5. Use Cases • Use cases are an analysis tool • They describe typical interactions between a user and the system • Capture some user-visible function • Achieve a discrete goal for the user • May be small or large

  6. Use Cases • Every system function/requirement must stem from some user-visible function • Take each discrete thing they want to do, give it a name, and write up a short textual description (no more than a few paragraphs).

  7. Use Case Diagrams • Used for visualizing use cases and helping to understand system interactions with the various kinds of users. • Part of the UML notation

  8. Actors • An actor is a role a user plays with respect to the system • There may be many persons playing the same role • One person can play more than one role • Actors carry out use cases • Actors don’t need to be human

  9. Use Case • Capture some user-visible function • Achieve a discrete goal for the user • A specification is attached to each use case

  10. RelationshipsCommunication Associations • Also called “links” • Relates an actor to a use case it interacts with

  11. Example:

  12. Useful for capturing exceptions Used for describing a variation in normal behavior The insertion of additional behaviour into a use case that does not know about it The Extend Relationship

  13. Example:

  14. The Include Relationship • Used when you have similar behavior across a number of use cases • In this case one use case uses another • Used when you are repeating yourself in two or more separate use cases and you want to avoid repetition • The insertion of additional behaviour into a use case that explicitly describes the insertion

  15. Example:

  16. Generalization Relationships • Used when you have one use case that is similar to another use case but does a bit more • The more specific use case inherits requirements from the more general use case and can add features to it

  17. Use Case Relationships

  18. Use Case Specifications Use Case name: Price Deal Category: Use Case View Documentation: This is some documentation for the Price Deal use case. You would provide one or two short paragraphs here. External Documents: Abstract: No State machine: No Generalization: Valuation (Uses) Associations: <no rolename> : Trader in association <no rolename> : Salesperson in association

  19. Teaching Points • What are Use Cases • Use Case Diagrams • Use Case Specifications

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