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

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.