Imran Hussain University of Management and Technology (UMT)

1. Virtual UniversityHuman-Computer Interaction Lecture 16HCI Process and Methodology Imran Hussain University of Management and Technology (UMT)

2. Open Your Eyes

3. In the Last Lecture • WIMP Interfaces • What are Paradigms • Paradigms of Interaction • Paradigm shifts (example) • Batch processing • Timesharing • Networking • Graphical display • Microprocessor • WWW • Ubiquitous Computing

4. In Today’s Lecture • Lifecycle Models • Software Engineering • Life-cycle Process Models • Waterfall Model • RAD Model • Spiral Model • HCI in Software Processes • Star Life-cycle Model • Usability Life-cycle Model • Some other models

5. Lifecycle Models • Show how activities are related to each other • Lifecycle models are: • management tools • simplified versions of reality • Many lifecycle models exist, for example: • from software engineering: waterfall, spiral, JAD/RAD, Microsoft • from HCI: Star, usability engineering

6. What’s the Problem? • Software costs are increasing as hardware costs decline. • Many software development disasters: • Cost overruns, late delivery • Reduced or wrong functionality, non-existent documentation • Many failures attributed to software • Cost of failure becoming very high: • Financial • Loss of life or loss of equipment • Inconvenience

7. Definition of Software Engineering • Fairley’s: • Software engineering is the technological and managerial discipline concerned with systematic production and maintenance of software products that are developed and modifiedon time and within cost estimates. • Engineering versus science: • Production, practical, quality, maintenance, reuse, standards, teams, management, etc.

8. SW Engineering Is and Is Not... • It is (or should be): • Engineering • Building software systems • Modifying software systems • A systematic, careful, disciplined, scientific activity • It is not: • Just building small systems or new systems. • Hacking or debugging until it works. • Easy, simple, boring or pointless

9. Software Lifecycle and Phases • Stages or phases that are typical in software development, from “birth” to “death” • There are various different models (more later) • Phases might include: • Requirements phase • Specification phase • Design phase • Implementation phase • Integration or “testing” phase • Maintenance phase • Also maybe “conception” and “planning”

10. Analogy: SE is like Construction • Think about how buildings come to be: • Requirements • Architecture • Construction • Differences? • Maintenance • Buildings don’t change much • Design • Buildings really are less complex • Number of states • Remove one brick

11. Requirements, Design, and Implementation • Requirements • Statements of what the system should do (or what qualities it should have) • From the customer or client point of view • Not expressed in terms of a solution • Design • A description of how we will implement a solution • A model or blueprint for meeting requirements • Done before implementation, so it can be evaluated • Many possible designs for a set of requirements. How to choose? • Often models are used to describe either of these

12. Three Key Elements in SE • Process: • life-cycle model used, project management and assessment, quality assurance, etc. • Method: • Approaches for solving a particular problem. The “how to’s” for doing some specific task. • E.g. object-oriented design; black-box testing; prototypes for requirements analysis. • Tools: • Software that supports methods and/or processes • CASE: Computer-aided Software Engineering • Test environments, 4GLs, Design tools, etc.

13. Example: Process, Method, Tools • Unit testing of code modules (before integration) • Process: How it’s to be done? When, who, etc.? • Documents: • Overall SW QA Plan • Software Test Plan • Based on design; includes test strategies, test cases, etc. for each module • Who? • Development team has a SQA lead • Perhaps a department or company SQA group • Independent testers, or tested by developers? • How do we verify (check) that its been done?

14. Example: Process, Method, Tools • Method: What approach to be used? • Example: Black box testing • Test cases, grouped into classes • Before testing, expected outcome is documented • After testing, did expected behavior occur? • Example: Testing for memory leaks • Tools: Software approach for process and methods • Test case generator: creates test cases • Regression test environment: repeats earlier tests • Memory leak tool • Problem reporting tool: keep problem database • Test-case matrix: which tests cover which requirements

15. Relative Cost Per Phase

16. Software Development Processes • Outline • What’s this all about? • Some example models for life-cycle • General principles

17. Life-cycle Process Models • Process means the events or tasks a development organization does, and their sequence • Again, think about construction • Organizations want a well-defined, well-understood, repeatable software development process. Why? • Find and repeat good practices • Management: know what to do next; know when we’re done with current task; know if we’re late; estimate time to completion, costs; Etc. • New team-members know what to do

18. Various Models for SW Lifecyles • “Historical Models” • Waterfall model • Spiral model • Government Standards • DoD standards: 2167, 2167A • FAA standard DO-178A, DO-178B • Corporate “Standards” or common practices • Many companies define their own. • Perhaps using: • Unified Process (was the Rational U.P.) • Extreme Programming

19. Why Learn About Process Now? • There are general principles of about: • What we do at various stages of SW development • How to inject quality into SW • How to avoid early problems that cause huge problems later • Recognize that SE is not just writing code

20. Waterfall Model • Early, simple model • Do the phases shown before, in order • Complete one phase before moving on to the next • Produce a document that defines what to do at the start of each phase • At end of each stage, a document or other work-product is produced: requirements doc, design doc, code, etc. • Little or no iteration (going back to previous phase) • The order of phases/stages is generally “right”, but… • Following the waterfall precisely is not effective in real development practice.

21. Traditional ‘Waterfall’ Lifecycle Requirements analysis Design Code Test Maintenance

22. Activities in the Life Cycle • Requirements specification • Designer and customer try capture what the system is expected to provide can be expressed in natural language or more precise languages, such as a task analysis would provide • Architectural design • High-level description of how the system will provide the services required factor system into major components of the system and how they are interrelated needs to satisfy both functional and non-functional requirements • Detailed design • Refinement of architectural components and interrelations to identify modules to be implemented separately the refinement is governed by the non-functional requirements

23. The formality gap Real-worldrequirementsand constraints Verification and Validation • Verification • designing the product right •  Validation • designing the right product • The formality gap • validation will always rely to some extent on subjective means of proof • Management and contractual issues • design in commercial and legal contexts

24. Flaws of the Waterfall • Need iteration and feedback • Things change (especially requirements) • Change late requires change in earlier results • Often need to do something multiple times, in stages • As described, it’s very rigid • Not realistic to freeze results after each phase • The model does not emphasize important issues • Risk management • Prototyping • Quality

25. A Quality-based View • People who do testing and SW Quality often re-draw the waterfall to emphasize testing activities that are not explicit in the last diagram • Is this a model organization a group can “follow”? • No. It’s a big-picture view for understanding. • A company might have a detailed standard plan (their process) • It could reflect this.

26. A Lifecycle for RAD (Rapid Applications Development) Project set-up JAD workshops Iterative design and build Engineer and test final prototype Implementation review

27. Spiral Model (Barry Boehm) • Important features: • Risk analysis • Prototyping • Iterative framework allowing ideas to be checked and evaluated • Explicitly encourages alternatives to be considered • Good for large and complex projects but not simple ones

28. Spiral Lifecycle Model

29. HCI in the Software Process • Software engineering and the design process for interactive systems • Usability engineering • Iterative design and prototyping • Design rationale

30. The Software Lifecycle • Software engineering is the discipline for understanding the software design process, or life cycle • Designing for usability occurs at all stages of the life cycle, not as a single isolated activity

31. Requirementsspecification Architecturaldesign Detaileddesign Coding andunit testing Integrationand testing Operation andmaintenance The Life Cycle for Interactive Systems lots of feedback! cannot assume a linearsequence of activitiesas in the waterfall model

32. A Simple Interaction Design Model Identify needs/ establish requirements (Re)Design Evaluate Build an interactive version Final product Exemplifies a user-centered design approach

33. The Star Lifecycle Model • Suggested by Hartson and Hix (1989) • Important features: • Evaluation at the centre of activities • No particular ordering of activities. Development may start in any one • Derived from empirical studies of interface designers

34. The Star Model (Hartson and Hix, 1989) Implementation task/functional analysis Requirements specification Prototyping Evaluation Conceptual/ formal design

35. Usability Engineering Lifecycle Model • Reported by Deborah Mayhew • Important features: • Holistic view of usability engineering • Provides links to software engineering approaches, e.g. OOSE • Stages of identifying requirements, designing, evaluating, prototyping • Can be scaled down for small projects • Uses a style guide to capture a set of usability goals

36. Other Process Models • The Unified Process • A widely-adopted process model in industry • Originally developed by Rational (now part of IBM) • More complicated model that what we’ve seen • Try looking for books on this with Google or at Amazon • Many light-weight or Agile Process Models • Best known example: Extreme Programminghttp://www.extremeprogramming.org • Look at the diagram. Compare to waterfall and spiral

37. Agile Process Models • Many developers and organization feel existing process models have been too “heavy weight” • Too many rules and documents. Inflexible. Not fun. • XP and many other agile methods try to be alternatives • XP says it’s: “a deliberate and disciplined approach to softwaredevelopment.” (So it is a process model.) • Claims to be good for risky projects with dynamic requirements, and when continuous customer involvement is crucial (and possible) • Emphasizes • Team development: pair-programming • Write tests before code (unit testing)

38. Final Thoughts on Process Models • Every organization does have a process • Might be chaos every time • But, should be defined, documented, planned and managed • Should be based on the nature of the projects the team is building • People have strong feelings on this subject about what works! • (IMHO) There is no “silver bullet” here. • I.e. no one thing that will solve all your problems all the time.

39. And here endeth today’s lesson