1. Usability Engineering Lifecycles
As Part of User-Centred Design
Major sources:
(Based on a PowerPoint Presentation obtained from Laura Leventhal at Bowling Green State Univ.)
Hix & Hartson: Chapters 4, 5
Developing User Interfaces Ensuring Usability Through Product & Process
by Deborah Hix and H. Rex Hartson
© 1993 by John Wiley & Sons, Inc.
Preece et al.:
Human-Computer Interaction
by Jenny Preece, Yvonne Rogers, Helen Sharp, David Benyon, Simon Holland, Tom Carey
© 1994 The Open University (Published by Addison-Wesley)
Mayhew:
The Usability Engineering Lifecycle: A Practitioner's Handbook for User Interface Design
©1999 by Morgan Kaufmann Publishers, Inc.
LCC QA76.9.U83M
ISBN
Continues on next slide

2. Usability Engineering Lifecycles
Notes (2 of 2)
Usability Engineering Lifecycles
Sources (cont.):
Denning & Dargan
A discipline of software architecture
By Peter J. Denning and Pamela A. Dargan
interactions v.I n.1 (Jan. 1994), pp. 55 – 65
<URL:
Curtis & Hefley
A wimp no more: the maturing of user interface engineering
By Bill Curtis and Bill Hefley
interactions v.I n.1 (Jan. 1994), pp. 22 – 34
<URL:

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

4. 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
Software explosion — forget crisis
Freefalling costs
Demand for increased functionality

5. Special Challenges to UI Development
The communications explosion
The media explosion
The usability explosion

6. 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

7. 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)

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

9. 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

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

11. Phases Systems engineering and analysis Software requirements analysis
Software design
Coding
Testing
Maintenance
Explain the phases
Show how they correspond to UI development
Use Figure 5 from Curtis & Hefley
Explaining the phases:
Systems engineering and analysis
Requirements gathering about the context of the software.
What other software, hardware, people, procedures etc., will the software interface with.
Software requirements analysis
Gathering requirements for the software itself.
Goals are to understand the nature of the program(s) to be built, the problem domain,
the required function, performance and (software) interfacing constraints.
The output of this phase is a software specification document.
Software design
Multistep processes that focusses on four distinct attributes of the program(s):
data structures,
software architectures,
procedural details, and
(software) interface characteristics.
The output of this phase is a software design document.
(Notes continue on next slide)

12. Phases Systems engineering and analysis Software requirements analysis
Software design
Code
Testing
Maintenance
Notes continued from previous slide
Code
Translate the design into machine-readable form.
The output of this phase is the code as well as the program documentation.
Testing
Once code is generated, begin testing.
Testing focuses on:
logical internals & code flows through the software, and
functional externals and how well the software meets the specifications.
The output from this phase is a testing report.
Maintenance
Software undergoes change after it is delivered or marketed.
Changes result from errors or because of external changes in the environment or because requirements change.
Maintenance uses a ‘mini’ form of the lifecycle for its changes.

13. Integrating UE Processes
Source: Curtis & Hefley, Figure 5, page 31.
Caption: Integrating User Interface Engineering Processes
Overhead slide is much clearer
Curtis & Hefley
Figure 5 (p. 31)

14. 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

15. 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

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

17. Spiral Model Common model for risky development Iteration is built-in
It is ‘rapid’ but still rigid
Barry Bane (long-A)
US Dept. of Defense
For real-time embedded systems
Risk analysis is what we would call task analysis/feasibility
Last ¼ is straight waterfall model
Permits revisiting of stages
Harder to evaluate costs, so
Use milestones for each iteration
Set maximum # of iterations
(Notes continue on next slide)

18. Spiral Model Continued from previous slide Image copied from
The Neume Notation Editor -- Spiral Model of Software Development
By Louis W. G. Barton
<URL: (19 June 2002)
Barton gives this credit for image:
Avelino J. Gonzalez and Douglas D. Dankel,
The Engineering of Knowledge-Based Systems, p. 299
(Englewood Cliffs, NJ: Prentice Hall, 1993).
Two other sources for similar images: Denning & Dargan or Oxford Dictionary of Computing
1) Denning & Dargan
See citation in note accompanying first slide
2) Oxford Dictionary of Computing:
3rd ed. (1991)
Figure (from IEEE Computer, May 1988, p. 62) on page 433
ISBN X

19. 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. 2.8, 18.5 in Preece et al.
Hix and Hartson (1993)
Figure 4.2 (page 102)
Preece et al.
Figure 2.8 (page 49)
Figure 18.5 (page 381)
Try not to mention extreme programming, please!
Inside-out programming: (p. 100 H&H)
‘the major work being the development of a good impedance match between what is at hand at the bottom and what is expected at the top’
Some description of ‘impedance’ on pp. 10 – 11
What is possible with the available tools, sometimes existing s/w base or tools limit what can be done
Extremely rare for any s/w to start de novo — it almost always builds on existing system or toolkit

20. Star Life Cycle Redrawn from Fig. 18.5 (p. 381) in Preece et al.
Definition of prototyping (for now): developing a working model

21. The Star Life Cycle Is… Not sequential Evaluation-centred
Activities can proceed in any order
Evaluation-centred
Each activity is evaluated
Interconnected
Through the evaluation in the middle
Primary activity that unites all phases is usability evaluation
How will we proceed?
Our approach is somewhat star-like
We do task analysis only once but we may do other steps more than once
Not a sequential model
Activities can proceed in any order
All phases are interconnected
Centred on user evaluation

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

23. 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
Show Curtis & Hefley Figure 5?

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