Usability Engineering Lifecycles

As Part of User-Centred Design

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What This Lecture Is About

1. The problem with software today2. Usability engineering lifecycles Next: early analysis activities

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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

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Special Challenges to UI Development

The communications explosionThe media explosionThe usability explosion

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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

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The Media Explosion

Mice, pens, touch screens, video, speech, VR etc.

UI code is half the codeGets more complicated, the more

the media (e.g., multimedia)

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The Usability Explosion

Users want availability (open architecture)

Increased awareness of costs of poor UIs

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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

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Waterfall Model (picture)

System Engineering

RequirementsAnalysis

Design

Coding

Testing

Maintenance

Classic Lifecycle Model

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Phases

Systems engineering and analysisSoftware requirements analysisSoftware designCodingTesting Maintenance

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Integrating UE Processes

Curtis & Hefley

Figure 5 (p. 31)

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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

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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

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Some Problems (2)

Customer must have patienceWorking version of the software will

not be available until late in the time span

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Spiral Model

Common model for risky development

Iteration is built-inIt is ‘rapid’ but still rigid

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Spiral Model

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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 & HartsonFigs 6.13 in Preece et al. (2002)Figs. 2.8, 18.5 in Preece et al. (1994)

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Star Life Cycle

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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

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Getting Started—specifics

SE/UI lifecycle divided into Definitional activities

(Called ‘early system analysis activities’)

Development/design activities

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Early System Analysis Activities

Documents concerned with Detailing the UI from the user’s

perspectiveGoal

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

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Review

Curtis & Hefley

Figure 5 (p. 31)