usability techniques for web-based services

CHI2000 1 Lindenberg, NeerincxPemberton, Van Dijk

Usability Techniques for Web-based Services

Diversity and Technology


Universal Accessibility

Design for All


General PrinciplesVanderheiden (1997)

• Use: equitable, flexible, simple and intuitive.

• Perceptible information and error tolerance.

• Low physical effort and appropriate size and space for approach.


Guidelines for ElderlyCzaja (1997)

• Contrast, screen glare, object size

• Minimal info, consistent location, group

• Highlight, color discrimination, key label

• Clear icons, practice

• Minimal demands on memory

• Consistency, simplicity (e.g. online help)


Web Content Guidelines (W3C)http://www.w3.org/TR/WAI-WEBCONTENT

• Auditory/visual alternatives/not color alone

• Markup and style sheets

• Natural language, tables, pages

• User control, access of embedded UIs

• Device independence, interim solutions

• W3C technologies, context information

• Clear navigation and simple documents


Conclusions

• Guidelines are available

• A coherent, complete, well-founded and practical set is lacking

• Techniques for application of the guidelines are scarce

=> Cognitive engineering framework


Cognitive Engineering (1)

empiricalsummative

analysis

designempiricalformative

analyticalformative

AssessmentSpecification

implemen-tation

flow of spec/assess task/processflow of iteration


practicaltheory

effectiveness,efficiency and

satisfaction

objectivesWeb-service

users, goals,info/ supportneeds and use context

specification

Cognitive Engineering (2)

assessment

data/info

task or process


Practical Cognitive Theory

Factors that affect Web-navigation:

• Spatial ability for mental modeling

• Memory capacity for task-set switching

• Situation awareness during interaction


Theoretical and Empirical BasedUser Requirements

for Elderly


Web-Navigation Performance

0

20

40

60

80

100

young elderly

% c

orre

ct in

fo a

cqui

sitio

n


Spatial Ability

0

5

10

15

20

25

30

35

young elderly

# co

rrec

t ch

oice

sMentalrotation

task

=> spatial representation


Memory Capacity

=> scheduler and goal creation

memorytask

0

10

20

30

40

50

60

70

young elderly

task

com

ple

tion

tim

e (s

)


News

ProductsIntroduction

FacilitiesDepartments

PeopleProjects

Request for information

Situation Awareness

=> multi-media, context and goal refinement

0

1

2

3

4

5

6

young elderly

corr

ect c

ateg

oris

atio

ns

categorisetask


Transform User Requirements into Navigation Support

for Elderly


Analysis

• Map user requirements on current support functions

• Prioritize according to “Web-service objectives”

• Estimate implementation costs

=> synthesize support concepts


Design and Implementation

Three support functions:

• categorizing landmarks

• history map

• navigation assistant


Evaluation

Three usability measures:

• effectiveness

• efficiency

• satisfaction


Example Satisfaction Results

1

2

3

4

5

None Landmarks Hist. map Assistant Combined

subj

ectiv

e us

abili

ty r

atin

g

youngelderly


Conclusions

• Individualization of Web-interfaces is needed to realize “Universal Accessibility”

• Design for all results in adaptive interfaces (no “boring uniformity”)

• Elderly users need more navigation support

usability techniques for web-based services

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