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Introduction to RE RE basics Requirements specification RE process RE specifics in web engineering

Introduction to RE RE basics Requirements specification RE process RE specifics in web engineering. System modeling Modeling requirements. Process of developing abstract models of a system Representing system using graphical notations UML.

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Introduction to RE RE basics Requirements specification RE process RE specifics in web engineering

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  1. Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  2. Introduction to RE • RE basics • Requirements specification • RE process • RE specifics in web engineering Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  3. System modeling • Modeling requirements Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  4. Process of developing abstract models of a system • Representing system using graphical notations • UML Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  5. each model presents a different view or perspective of the system • External perspective: system context and environment • Interaction perspective: how system interact with environment • Structural perspective: how system is organized • Behavioral perspective: dynamic behavior of the system Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  6. Models are used during • RE phase to derive system requirements • use-case diagram, activity diagram • design phase to describe the system to engineers • class diagrams, sequence diagrams etc. • after implementation • to document system’s structure and operation Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  7. Why system modeling? • reduce complexity • document design decisions • facilitate communication among team members Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  8. Levels Modeling dimensions: • Levels – the “how” & “what” of an application • Aspects – objects, attributes, and relationships; function & processes • Phases – Development cycle User interface Application Logic Phases Structure Analysis Design Implementation Behavior Aspects Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  9. “The Unified Modeling Language is a visual language for specifying and documenting the artifacts of systems” • Structural – Class diagrams • Behavioral – Use Case diagrams, State machine diagrams Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  10. Levels Presentation • Levels – Information, node/link structure, UI & page layout separate. • Aspects – Same as Software Applications • Phases – Approach depends upon type of application • Customization – Context information (user’s preferences, bandwidth restriction, device characteristic etc.) and allow to adopt web application accordingly • Influence other three dimensions Hypertext Customization Content Phases Structure Analysis Design Implementation Behavior Aspects Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  11. Requirement modeling • use-case diagram • activity diagram • Content modeling • class diagram • Navigational modeling • to model nodes and navigational structure among them • Presentation modeling • model user interface, page-layout Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  12. For Web-centric modeling, UML is used with some extensions from UWE (UML-based web engineering) • http://uwe.pst.ifi.lmu.de/ Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  13. Use-case Diagram: The goal of the diagram is to provide a high-level explanation of the relationship between the system and the outside world (set goals) • Activity diagram: a graphical representation of workflows of stepwise activities and actions with support for choice, iteration and concurrency Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  14. Components: • The system • Theuse case task referred to as the use case that represents a feature needed in a software system System Name Use-case title Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  15. Components: • The actor(s) who trigger the use case to activate • Thecommunicationline to show how the actors communicate with the use case <<actor>> HR system Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  16. Theinclude relationship represents the inclusion of the functionality of one use case within another • Theextend relationship represents the extension of the use case to include optional functionality <<include>> base use-case include use-case <<extend>> Extension use-case Base use-case Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  17. Ause-case-generalizationis a relationship from a child use case to a parent use case, specifying how a child can specialize all behavior and characteristics described for the parent Generalized Specialized Registered user user Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  18. Web specific requirements: • Need to distinguish between functional and navigational use-cases • UWE provides <<browsing>> to represent a navigational use-case while <<processing>> to represent a functional use-case Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  19. Consider an online video sharing system: • Users can search and view the videos • A user must be a register user to share videos Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  20. Online video sharing system <<browsing>> Search a video user <<browsing>> Watch a video <<processing>> register <<extend>> <<processing>> Registered user <<browsing>> share a video login <<include>> Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  21. Elements of an activity diagram: • An activity is a step in a process where some work is getting done • The transition takes place because the activity is completed activity Read a page Turn the page Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  22. Elements of an activity diagram: • A guard condition can be assigned to a transition to restrict use of the transition [get driving license] Learn driving Drive the car Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  23. Decisions • Merge point • Start and end Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  24. User fill in the registration form User selects submit button User corrects input No System shows error message Correct ? User is registered Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  25. UWE activity diagram elements: • userAction : user’s action or response • systemAction : system’s action • displayAction : display action • navigationAction : navigation • displayPin : output • interactionPin : input Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  26. <<displayAction>> registratinForm {type=form} name {type=text} Email {type=email} Password {type=password} <<systemAction>> saveData <<userAction>> inputData {validated} name email password Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  27. System modeling • Modeling Requirement • use-case diagram • activity diagram Basharat Mahmood, Department of Computer Science,CIIT,Islamabad, Pakistan.

  28. Chapter 3, Kappel, G., Proll, B. Reich, S. & Retschitzegger, W. (2006). Web Engineering, Hoboken, NJ: Wiley & Sons • Chapter 5, Sommerville, Software Engineering, ISBN-10: 0-13-703515-2 , PEARSON Basharat Mahmood, COMSATS Institute of Information Technology, Islamabad, Pakistan.

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