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What is the relationship between usability and accessibility, and what should it be?

Dey AlexanderUsability Specialist, Web Resources and Development

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Lots of talk about it

• Some people are concerned about the relationship between usability and accessibility

– Online survey 2003 by Usability News – British HCI Group

– 56% (of 117 respondents) agreed “there is a conflict between usability and accessibility”.

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More talk of potential conflict

Peter-Paul Koch

“The delicate balance between accessibility and usability needs more thought. At the moment I don't see any answers, only a few questions, one possible rule, and a potential danger. The rule is "Accessibility should not restrict usability”.

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Common questions

• Are usability and accessibility compatible design approaches?

• Does accessibility improve

usability for other users?

• Does usability improve accessibility?

• How does the relationship between accessibility and usability affect practitioners?

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Some starting points for our discussion

• What is it?– What is accessibility?

– What is usability?

– How are they defined?

• How is it done?– What do practitioners in each field do?

– What methods/techniques do they use?

• Common expressions of the relationship• Return to our original questions

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Definition of usability – from the guru

Jakob Nielsen

Usability is the measure of the quality of the user experience when interacting with something - whether a website, a traditional software application, or any other device the user can operate in some way or another.

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Definition of usability – practitioner’s view

Whitney Quesenbery

The 5 Es of usability• Effective• Efficient• Engaging• Error tolerant• Easy to learn

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Formal definition of usability

ISO 9421

Usability is a measure of the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in a particular environment.

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Definition of accessibility – from the guru

Tim Berners-LeeFounder of the web

The power of the web is in its universality. Access by everyone regardless of disability is an essential aspect.

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Definition of accessibility – practitioner’s view

Jim Thatcher

Basically, technology is accessible if it can be used as effectively by people with disabilities as by those without.

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Formal definition of accessibility… sort of

These guidelines explain how to make Web content accessible to people with disabilities…

The primary goal of these guidelines is to promote accessibility. However, following them will also make Web content more available to all users, whatever user agent they are using (e.g., desktop browser, voice browser, mobile phone, automobile-based personal computer, etc.) or constraints they may be operating under (e.g., noisy surroundings, under- or over-illuminated rooms, in a hands-free environment, etc.).

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Two key differences

Users Design goals

Usability Varies each time

Improve user experience, ease of use

Accessibility

Always the same

Remove barriers to access, equitable use

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Design philosophy radically different?

• Universal vs particular– One size does not fit all

– One size does fit all

• But are they really like chalk and cheese?

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Notions of universality in usability

• Usability heuristics developed by Nielsen and Molich• Heuristics are broad guidelines or principles that are

indicators of usability in all user interfaces • Similar in breadth to universal design principles• Similar themes, despite different design domains

– Flexibility

– Error tolerance

– Simplicity

– Effort minimisation

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Example of similar themes

• Flexibility in use (UD)– The design accommodates a wide range of

individual preferences and abilities.

• Flexibility and efficiency of use (Heuristic)– Accelerators -- unseen by the novice user --

may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

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Universal design acknowledges difference

• Universal design is about flexible and inclusive design

• IMS AccessForAll specification– Makes it possible to identify resources that match

a user's stated preferences or needs

• Web4All project in Canada– Utilises smart card technology which allows

Internet uses to select, save and store their preferences

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Similarities

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Differences

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Usability methods and practices

• Competitor research• Web server log and search log analysis• Surveys, interviews, focus groups• Contextual inquiry, field studies• Task analysis• Design guidelines, standards, patterns• Card sorting• Prototyping, walkthroughs• Standards inspection, heuristic evaluation• User testing

}UCD

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Accessibility methods and practices

• Design guidelines (for web content)– WCAG 1.0 (2 in development)

– Section 508

• Conformance evaluation– Manual inspection

– Automated inspection

– User testing

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Comparison based on methods

• Number of methods differ• Methods are roughly

equivalent– Conformance evaluation and

standards inspection

– User testing differences

• But all usability methods could be used in designing for people with disabilities

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Compatible design approaches

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Differences in accessible design practice

• Strong reliance on design guidelines

• Absence of design research methods

• Lack of focus on user-centred design

– User involvement

– Design iteration

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Work by the ITTATC at Georgia Institute

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Differences in usability practices

• People with disabilities are invisible

• “There is no market for accessible design”

• Accessible design is seen as an optional extra

• No recognition of the business benefits of accessible design

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Common expressions of the relationship (1)

• One is a subset of the other

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Accessibility: technical and human interaction

Section 508

– (l) When pages utilize scripting languages to display content, or to create interface elements, the information provided by the script shall be identified with functional text that can be read by assistive technology.

– (o) A method shall be provided that permits users to skip repetitive navigation links."

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Accessibility: technical and human interaction

WCAG 1.0

– 3.2 Create documents that validate to published formal grammars.

– 14.1 Use the clearest and simplest language appropriate for a site's content.

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It’s not a neat fit

• Usability specialists deal with designing the user interface

• Technical design is the province of developers

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Common expressions of the relationship (2)

• Accessibility is a prerequisite, i.e. a necessary, but not sufficient condition for usability

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Again, it’s not a neat fit

• Accessible design guidelines also include guidelines that relate to user interface design

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What is the relationship?

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Are usability and accessibility compatible?

• Yes they are– Share some concern

for universal design

– Share some design and evaluation techniques

– Could (and should) share more practices

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Do design requirements conflict?

• Perhaps, but so do different sets of usability guidelines.

• Design guidelines are not the holy grail

• Design is about looking for solutions within a set of constraints

• Solutions require user research and testing

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Zeldman (on Clarke) on guidelines

Accessibility is not the memorisation of a set of rules, but, like other aspects of design and usability, it's something to think about. It's something filled with challenges. It's something that intelligent and reasonable people can disagree about. There's more than one right way to do something.

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Does accessibility improve usability?

• In many cases, yes• Examples:

– Providing site maps

– Clearly identifying the target of a link

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Does usability improve accessibility?

• In many cases, yes• Examples:

– Writing concisely and in plain English

– Clear and simple navigation

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Implications for practitioners

• Need to share specialised knowledge and expertise across the two fields

• Need to collaborate and learn each others’ methods and techniques

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Conclusions (1)

• Focusing on the possibility of guideline clashes is a red herring

• Design isn’t only about guidelines, nor which set of guidelines should trump the other

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Conclusions (2)

• Accessibility practitioners should embrace the practices of their usability counterparts by:

– Ensuring that the requirements for accessible design are made explicit in the requirements phase of projects

– Engaging in design research in addition to knowing how to apply accessible design guidelines

– Adopting user-centred methods

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Conclusions (3)

• Usability practitioners should embrace the practices of their accessibility counterparts by:

– Making clients aware of the growing market for accessible design

– Educating clients about the business benefits of accessible design

– Discharging their professional responsibility to advise clients of relevant legislation, in this case the requirements of anti-discrimination legislation

– Making disabled users visible by including them in their design practices.

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Want more?

• Relax, we’re out of time!– Paper and detailed references online at

http://deyalexander.com/presentations/usability-accessibility/