CS 501: Software EngineeringAdministrationSlide 3Requirements Analysis v. System DesignModels: Useful TextsModelsPrinciples of ModelingThe Unified Modeling LanguageRational RoseDiagrams and Specification in UMLActor and Use Case DiagramUse Cases and ActorsScenarioScenario: a Typical StudentScenario (continued)Slide 16Modeling Scenarios as User CasesUse Cases for Quiz SystemSlide 19Relationships Between Use Cases: <<includes>>Relationships Between Use Cases: <<extends>>Specification of Use CaseSpecification of Use Case (continued)Use Cases in the Development CycleDocumentation: GeneralDocumentation of Requirements Specification: PurposeRequirements Specification: PurposeSlide 28Requirements Specification: DetailsRequirements Specification: Process1CS 501 Spring 2006CS 501: Software EngineeringLecture 8Requirements II2CS 501 Spring 2006AdministrationQuiz 1If you did not pick it up on Tuesday, you can collect your quiz from reception at 301 College AvenueAssignment 1: Feasibility studyDue Friday at 5:00 p.m.Remember to send a copy to your clientThe survey has not yet been posted.3CS 501 Spring 2006AdministrationGForgeA new page has been added to the Web site with information about GForge.4CS 501 Spring 2006Requirements Analysis v. System DesignDilemma. • Requirements analysis should make minimal assumptions about the system design.• But the requirements definition must be consistent with computing technology and the resources available.In practice, analysis and design are interwoven. However:1. Do not to allow the requirements analysis to prejudge the system design.2. Do not allow assumptions about the design to influence the requirements analysis.5CS 501 Spring 2006Models: Useful TextsGrady Booch, James Rumbaugh, Ivar Jacobson, The Unified Modeling Language. Addison-Wesley 1999.Grady Booch, Object-Oriented Analysis and Design with Applications, second edition. Benjamin/Cummings 1994.Rob Pooley, Perdita Stevens, Using UML Software Engineering with Objects and Components. Addison-Wesley 1999.6CS 501 Spring 2006ModelsA model is a simplification of reality.• We build models so that we can better understand the system we are developing.• We build models of complex system because we cannot comprehend such a system in its entirety.Models can be informal or formal. The more complex the project the more valuable a formal model becomes.BRJ7CS 501 Spring 2006Principles of Modeling• The choice of what models to create has a profound influence on how a problem is attacked and how a solution is shaped. • Every model can be expressed at different levels of precision.• The best models are connected to reality.• No single model is sufficient. Every nontrivial system is best approached through a small set of nearly independent models.BRJ8CS 501 Spring 2006The Unified Modeling LanguageUML is a standard language for modeling software systems• Serves as a bridge between the requirements specification and the implementation.• Provides a means to specify and document the design of a software system.• Is process and programming language independent.• Is particularly suited to object-oriented program development.9CS 501 Spring 2006Rational RoseRational Rose is an IBM-owned system for creating and managing UML diagrams.It is available for Computer Science Department computers.10CS 501 Spring 2006Diagrams and Specification in UMLA diagram is the graphical representation of a set of elements, usually rendered as a connected graph of vertices (things) and arcs (relationships).Each diagram is supported by technical documentation that specifies in more detail the model represented by the diagram.A diagram without documentation is of little value.11CS 501 Spring 2006Actor and Use Case Diagram• An actor is a user of a system in a particular role. An actor can be human or an external system.• A use case is a a task that an actor needs to perform with the help of the system.Borrow bookBookBorrowerUse cases make more precise the concept of viewpoint analysis.12CS 501 Spring 2006Use Cases and Actors• A scenario is an instance of a use case • Actor is role, not an individual(e.g., librarian can have many roles)• Actor must be a "beneficiary" of the use case(e.g., not librarian who processes book when borrowed)In UML, the system boundary is the set of use cases.13CS 501 Spring 2006ScenarioA scenario is a tool used during requirements analysis to walk through a specific interaction with a proposed system.ExampleThe requirements are being developed for a system that will enable university students to take quizzes online from their own rooms using a Web browser.Create a scenario for a typical student.14CS 501 Spring 2006Scenario: a Typical StudentIndividual: Philip Glass, senior at Cornell, major in computer science, location Risley Hall.Equipment: Dell laptop attached to Cornell dormitory network. Firefox 1.5 browser and Sidecar authentication system installed.Scenario: 1. PG powers up computer and authenticates using Sidecar.2. PG starts browser and types URL of Quiz system.3. Quiz system displays list of options.15CS 501 Spring 2006Scenario (continued)4. PG selects CS 501 Quiz 1.5. A list of questions is displayed, each marked to indicate whether completed or not.6. PG selects a question and specifies whether he will submit a new answer or edit a previous answer.7. For the first question, he is submitting a new answer. He has a choice whether to type the solution into the browser or to attach a separate file. He decides to attach a file.8. For the second question, he is editing a previous answer. He chooses to delete a solution previously typed into the browser, and to replace it with an attached file.16CS 501 Spring 2006Scenario (continued)9. PG has now completed the quiz. He selects an option that submits the quiz to the grading system.10. PG now wishes to change a solution. The system does not permit changes once the solution has been submitted.11. PG logs off.17CS 501 Spring 2006Modeling Scenarios as User CasesA scenario is useful in discussing a proposed system with a client, but needs to be generalized as part of the requirements modeling.A use case provides such a model.18CS 501 Spring 2006Use Cases for Quiz SystemTakeQuizQuizTakerCheckGradesRequestRegrade19CS 501 Spring 2006Use Cases for Quiz SystemSetQuizInstructorGradeRegradeNote that actor is a role. An individual can be a QuizTaker on one
View Full Document
Unlocking...