(面向对象的设计)Part2INCEPTION.pptVIP

6.5. Are Use Cases Functional Requirements? Use cases are requirements, primarily functional or behavioral requirements that indicate what the system will do. 6.6. What are Three Kinds of Actors? Primary actor has user goals fulfilled through using services of the SuD ( System under Discussion) the cashier. Supporting actor provides a service to the SuD. the automated payment authorization service Offstage actor has an interest in the behavior of the use case, but is not primary or supporting; a government tax agency. 6.7. What are Three Common Use Case Formats? Brief terse one-paragraph summary, usually of the main success scenario. Process Sale Casual informal paragraph format. Multiple paragraphs that cover various scenarios. Handle Returns Fully dressed all steps and variations are written in detail, and there are supporting sections 6.8. Example: Process Sale, Fully Dressed Style Use Case Section Comment Use Case Name Start with a verb. Scope The system under design. Level user-goal or subfunction Primary Actor Calls on the system to deliver its services. Stakeholders and Interests Who cares about this use case, and what do they want? Preconditions What must be true on start, and worth telling the reader? Success Guarantee What must be true on successful completion, and worth telling the reader. Main Success Scenario A typical, unconditional happy path scenario of success. Extensions Alternate scenarios of success or failure. Special Requirements Related non-functional requirements. Technology and Data Variations List Varying I/O methods and data formats. Frequency of Occurrence Influences investigation, testing, and timing of implementation. Miscellaneous Such as open issues. 6.9. What do the Sections Mean? Preface Elements Scope: NextGen POS Application bounds the system (or systems) under design Level: User goal user-goal common kind that describe the scenarios to fulfill the goals of a primary actor to get work done subfunction-level s