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Usability Engineering Lifecycles

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  1. Usability Engineering Lifecycles As Part of User-Centred Design

  2. What This Lecture Is About • The problem with software today • Usability engineering lifecycles • Next: early analysis activities

  3. Building a UI — What Do We Know? • Principles of UI development are neither obvious nor intuitive • Principles of UI development are not applied as often as they should be • Developing a UI is part of the larger problem of developing software • What are the big trends driving the field today? • The software crisis • Software chronic problem

  4. Special Challenges to UI Development • The communications explosion • The media explosion • The usability explosion

  5. The Communications Explosion • Essence of UI used to be one-user, standalone. Now moving more toward connectivity (e.g., WWW, CSCW, etc.) • Superhighway; Communications services; Expanding user pops

  6. The Media Explosion • Mice, pens, touch screens, video, speech, VR etc. • UI code is half the code • Gets more complicated, the more the media (e.g., multimedia)

  7. The Usability Explosion • Users want availability (open architecture) • Increased awareness of costs of poor UIs

  8. The SE S/W Dev. Life Cycle Plus UE • Waterfall model • Systematic, sequential approach to software development • Begins at system level and progresses through a series of phases

  9. Waterfall Model (picture) System Engineering Classic Lifecycle Model Requirements Analysis Design Coding Testing Maintenance

  10. Phases • Systems engineering and analysis • Software requirements analysis • Software design • Coding • Testing • Maintenance

  11. Integrating UE Processes Curtis & Hefley Figure 5 (p. 31)

  12. Issues for Waterfall Model • The waterfall model is the oldest and most widely-used paradigm for software engineering • Following any methodology imposes discipline on the software development process • It appears to be easy to specify a timetable and costing for s/w developed with the waterfall model

  13. Some Problems (1) • Real problems rarely follow the sequential flow that model suggests: • Iteration always occurs and • Creates problems in the application of the paradigm • Difficult for customer to state all requirements explicitly: • Life cycle has difficulty accommodating uncertainty that exist at beginning of many projects

  14. Some Problems (2) • Customer must have patience • Working version of the software will not be available until late in the time span

  15. Spiral Model • Common model for risky development • Iteration is built-in • It is ‘rapid’ but still rigid

  16. Spiral Model

  17. The ‘Let's Get Real’ Model • Hix & Hartson observed that UI developers worked in ‘alternating waves’ of top-down, bottom-up, inside-out, … • See Star Life Cycle figure • Fig. 4.2 in Hix & Hartson • Figs 6.13in Preece et al. (2002) • Figs. 2.8, 18.5 in Preece et al. (1994)

  18. Star Life Cycle

  19. The Star Life Cycle Is… • Not sequential • Activities can proceed in any order • Evaluation-centred • Each activity is evaluated • Interconnected • Through the evaluation in the middle

  20. Getting Started—specifics • SE/UI lifecycle divided into • Definitional activities (Called ‘early system analysis activities’) • Development/design activities

  21. Early System Analysis Activities • Documents concerned with • Detailing the UI from the user’s perspective • Goal • Produce detailed documents that spell out as specifically as possible what the UI for the product will be like • Details • See the ‘early analysis activities’ slides

  22. Review Curtis & Hefley Figure 5 (p. 31)