Skrýt videa s překladem do znakového jazyka
Zvětšit přes celou obrazovku
Česky English version of this page

Detail příspěvku

Measuring real accessibility - Pavlíček, Radek

Radek Pavlíček, Roman Kabelka
Masaryk University, Brno, Czech Republic


How to determine the real accessibility of websites? Is a web page with ten headings more accessible than another page with only four headings?

Accessibility is nowadays often a part of laws. Risk of ligitation, moral and political pressure force site owners, designers and developers to ensure that their sites are accessible. Very often they need “a proof” of accessibility and they face the tasks of deciding what is the most efficient and reliable way of evaluating accessibility.
Accessibility is strongly influenced by a lot of factors and it is very short-sighted to narrow accessibity down only to technical factors – quality of HTML code and CSS, its validity, etc. Other factors are for example
  • user disability (both health and technical),
  • user knowledge of using web itself,
  • used browser,
  • used assistive technology,
  • user knowledge of assistive technology,
  • user preferences and habitual practices.

Let’s see typical internetbanking. It is not fully compliant with any guidelines (eg. WCAG 2.0), but people with disabilites commonly use it – because they need it and they have power tools (browsers and assistive technologies) and enough knowledge to do it. Other typical examples are social networks such as Facebook or Google+.

All aspects mentioned above has to be taken in mind if you want to speak about accessibility. User-centered view and focus on user instead on technology and rules is much better and chime in with real aspects of accessibility. Users aren’t interested in compliance with guidelines. Their demand is simple – use the web and accomplish the task that they need.
Each webpage has its own main objective and this objective should be the key – if a person with disability is able to complete his or her task with tools which he or she has available, in way which he or she prefers, the website is accessible for him or her.
On the other hand, giving a definition and setting some rules and guidelines help webdevelopers to know what is best practice and learn the way leading to the true aim.
Accessibility metrics provide a valuable role in establishing the extent to which a web resource can be effectively used by people with specific access needs. Measuring accessibility should not be restricted to web pages; but rather the extent to which goals can be completed by disabled people relative to other members of the target audience. This can cover alternative equivalent routes, using alternative online resources if necessary or alternative access means (eg. screenreaders or screen magnifiers). This definition of course contains more subjective, experiential issues, that may modify the apparent impact of a specific accessibility barrier – but real life isn’t only black or white.
There are typically two approaches how to measure the web accessibility. “Conformance review” approach that rely on some checklist and “user testing” approach – some form of user testing by people who have different disabilities and/or who rely on different assistive technologies.
Conformance review is a typical way of evaluation of web sites accessibility. In general, this involves someone with expert knowledge checking whether the site as a whole, or more commonly a selection of pages, comply with a some guidelines (predetermined checklist of criteria) such as WCAG 2.0. This process is sometimes called “accessibility audit”.
User testing is usually carry out by a group of users with different disabilities, and different levels of skill in using the internet and their required assistive technology. These users undertake a series of typical website tasks. Their actions are observed (and sometimes recorded) by the evaluator with the aim of identifying the accessibility barriers that maybe encountered.
Both approaches have their strength and limitations, and neither can provide a reliable declaration about the accessibility of a site on its own.
At the very beginning of Blind Friendly Web project, we had relied only on guidelined approach to the accessibility. After some years, when we often had met limitations of this approach, we started to combine “guidelined” with “user-centered” approach. Now our typical web accessibility test contains results of both approaches. Accessibility expert evaluates web for conformance with some methodology/guidelines and group of 6 users with various visual impairment undertakes some (3 or 4) typical website tasks.
This combination brings more realistic view on web accessibility. Users evaluate the possibility to fullfil their needs and accessibility expert can find barriers, that users aren’t able to find – for example blind tester isn’t able to assesses sufficient contrast of text and background color.
Our testing model unfortunately has one weekness, that we would like to “fix” – ideal user group should cover all (or let’s say all major) group of users with disabilities – not only user with visual impairment. But on the other hand – it’s better to have one group of testers than none.
Our solution for now is following. Now accessibility expert in specific way “stands in for” disabilities, that aren’t cover in user testing, because guidelines are usually more general and cover needs of more than one group of disability users.
Based on our experience and despite the weekness mentioned above, the combination of “guidelined” and “user-centered” view is now the best solution how to measure real web accessibility.
Hudson, Roger. Measuring Accessibility [online]. DingoAccess. 2011 [cit. 1. 2. 2012]. Available in English at www.dingoaccess.com/accessibility/measuring-accessibility.
W3C. Website Accessibility Metrics. Online Symposium 5 December 2011. [cit. 1. 2. 2012]. Available in English at http://www.w3.org/WAI/RD/2011/metrics.
Pavlíček, Radek. Does user testing miss its goal? Poslepu.cz. 2009 [cit. 1. 2. 2012]. Available in Czech at http://poslepu.blogspot.com/2009/05/miji-uzivatelske-testovani-pristupnosti.html.

Pro plný text, prezentaci a videozáznam se prosím přihlašte.