Adaptive web accessibility metrics

Adaptive Web Accessibility Metrics

Markel Vigo1 and Giorgio Brajnik2

1 Laboratory of Human Mobility and Technology

2 University of Udine

BCS HCI Workshop: The socio technological issues of adaptive interfaces and user ‐profiling for accessibility

September 6, Dundee (Scotland)

1. Motivation for Adaptive Accessibility Metrics

Adaptive Web Accessibility Metrics Vigo & Brajnik, 2010

• We’d like to know the answer to this question:“To what extent is accessible a web page…

- for a determined user with their own abilities - using a determined Assistive Technology and user agent - operating a specific device - and carrying out a determined task”

• …equals to measuring accessibility in use or contextual accessibility

• Traditional web accessibility metrics aim at measuring accessibility wrt to conformance

• There are some scenarios that could benefit- As a way to measure interface adaptations- Adaptive hypermedia techniques- Accessibility observatories and QA

1. Motivation for Adaptive Accessibility Metrics


•Why adaptive accessibility scores?- Do conformance scores capture the accessibility perceived by users?

- Traditional metrics are based on general purpose guidelines

- Assuming metrics are adequate and valid many error-rates are introduced

- Trusting in guidelines is risky

- Guidelines do not capture all users’ needs and interaction context• We need accessibility scores that capture the interaction context

• Metrics are tied to evaluation process

• Adaptive evaluation would produce user-tailored scores

• Better if scores are automatically obtained

2. Challenges and Engineering solutions


• Select only those guidelines that impact on a determined user group

Challenge 1: how to capture interaction context data (non intrusively)

• Not enough

• Context is key for adaptive evaluations

• Detecting installed Assistive Technology and user agents is a step forward

• Evaluation tools need a user profile as an input



• Weight barriers for a specific user context

Challenge 2: quantify severity of violated accessibility barriers

• Application scenarios require real-time scores

• How to quantify barriers automatically?

• Make use of infrastructures such as Accessibility Commons

• Accessibility metadata stored beforehand

• Triples: <accessibility problem, context, severity>



• Not to tie the metric to a determined guideline set

Challenge 3: reasoning over guidelines

• No matter which guideline set is used the metric should adapt to it

• Guidelines have to be specified in a common language so that evaluation tools can understand them interoperability • Metrics require parameters such as number of applied guidelines, severities, etc inference• Interoperability + inference = ontologies?

Adaptive Web Accessibility Metrics

Markel Vigo1 and Giorgio Brajnik2

1 Laboratory of Human Mobility and Technology

2 University of Udine

BCS HCI Workshop: The socio technological issues of adaptive interfaces and user ‐profiling for accessibility

September 6, Dundee (Scotland)

Adaptive web accessibility metrics

Technology

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