1. Web Applications and Services Introduction to Web Engineering

2. Today’s Topics l Software and the World Wide Web l Implications and Challenges l Application & Technology Types l The WebE Process l Analysis, Design & Testing Issues l Management Issues

3. The Wild, Wild Web l Chaotic growth and application of new technology l “Get it done fast, get it on the web, fix it up later” l Little, attention paid to software process (ad hoc approach) l Very rapid software development, strict performance requirements, high technical risk

4. Implications l Very high cost of software construction and maintenance l Poor software infrastructure for long-term support l Lack of software quality In the days ahead - as the dot-com revolution slows and investors look for sound business models, planning, and profitability - an engineered approach to web software will grow in importance…

5. Challenges How to adapt SE methods? WebApps have these attributes: l Network Intensive large-scale client-server (Internet) l Content-Driven text, graphics, audio, video, … l Continuous Evolution some sites are updated hourly

6. Challenges [2] l Immediacy time to market = days or weeks l Security difficult to control access strong security measures required l Aesthetics look & feel > technical design?

7. Application Categories l Informational read-only content, simple linking l Download variety of data types downloaded l Customizable user personalizes site content l Interaction supports community of users

8. Categories [2] l User Input HTML forms-based input data l Transaction-Oriented user requests (e.g. on-line orders) l Service-Oriented searches, advice, brokering, etc. l Portal links a variety of content, services

9. l Database Access query & extract information l Data Warehousing access collections of databases Categories [3]

10. Defining Quality [from SEPA 5/e]

11. Fundamental Technology l Component-Based Development CORBA, COM/DCOM, EJB: web deployment architectures l Security policy & appropriate design l Internet Standards HTML, XML, HTTP, CGI, etc.: web communication protocols

12. The WebE Process l Immediacy & continuous evolution  iterative, incremental process l User population is diverse  extensive user modeling l Architecture is highly specialized  complex design l Content emphasizes aesthetics  content designed in parallel

13. WebE Process Model [from SEPA 5/e]

14. Formulation l General Questions What is the motivation for the app? Why is the app needed? Who will use the app? l Specific Goals Informational Goals content & information provided Applicative Goals ability to perform specified tasks l Statement of Scope (Integration)

15. Analysis l Content Analysis identify, model content spectrum l Interaction Analysis use cases, sequence diagrams l Functional Analysis specify all required operations l Configuration Analysis specify environment, infrastructure Accurate estimates of schedule & cost depend on a detailed analysis!

16. The “Designer’s Dilemma” l “Solve the immediate business problem, while defining an architecture than can evolve over time” l Otherwise, you make compromises that force costly rework or a loss of quality over time

17. Four Design Elements l Design Principles & Methods modularity & information hiding; UML modeling & O-O design l Golden Rules design heuristics for hypermedia l Design Patterns functions, documents, graphics,… l Templates reusable, skeletal structures

18. Architecture Design Define overall site structure: l Linear Structures predictable sequence of operations l Grid Structures two-dimensional categorization l Hierarchical Structures “convenience vs. confusion” l Networked “flexibility vs. confusion”

19. Linear Structures [from SEPA 5/e]

20. Grid Structure [from SEPA 5/e]

21. Hierarchical Structure [from SEPA 5/e]

22. Networked Structure

23. Hypertext Design Patterns l Cycle return to previously visited node l Web Ring “grand tour” of a subject l Contour intersecting cycles l Counterpoint provide additional narrative

24. Design Patterns [2] l Mirrorworld provide alternate perspectives l Sieve provide choices which guide user l Neighborhood consistent navigation overlay

25. Navigation Design “Defining pathways to content and services”: l Identify differing user navigation requirements & goals will differ per user type l Define the mechanics of achieving navigation may differ per user type

26. Navigation [2] l Select from available mechanisms links, buttons, imagemaps, menus l Optimize navigation minimize user effort l Respect other criteria site aesthetics & content design l Adopt conventions audiovisual cues, feedback, maps

27. Interface Design l “First impression is everything” l Server errors are deadly l Minimize volumes of text l Avoid “under construction” signs l Avoid long pages & scrolling l Navigation aids everywhere l Functionality > Aesthetics

28. Testing Web Applications l Review the content model like copy-editing written docs l Review the design model identify navigation errors l Unit test components & pages content, links, forms, scripts, etc. l Integration testing build & test the architecture; thread-based testing on use cases

29. Testing [2] l Perform validation testing test all user-visible actions, output l Perform cross-platform testing hardware, OS, browser, etc. l Perform user testing tester population covers all possible user roles

30. The WebE Team l Content developers & providers sales, marketing, research, … l Web publisher liaison between technical staff and content developers l Web engineer SE activities, web technologies

31. WebE Team [2] l Support specialist continuing day-to-day support l Administrator (“Webmaster”) day-to-day operation Operational policies Support & feedback process Security policy & procedures Traffic analysis Change control & support coordination

32. Management & Outsourcing l Many web apps are outsourced to development specialists analyze, specify & plan internally l Little historical data, metrics define explicit progress reviews l Accurate estimation, risk planning & scheduling require detailed understanding of scope constant communication

33. Configuration Management l Haphazard updates are dangerous: Unauthorized posting of new info Erroneous or poorly-tested functions Security holes “Economically unpleasant consequences” l Four issues: content, people, scalability, politics

34. Questions?