Interrelationship between Accessibility and Usability
As mentioned my previous blog posting, Web Accessibility means that people with disabilities can use the Web - they can perceive, understand, navigate and interact with the Web. Usability on the other hand means that products – IT or otherwise – are easy to learn, easy to memorize, can be used without making errors and allow the users to accomplish tasks efficiently.
The ISO (International Organization for Standardization) defines Usability as the “extent to which a product can be used by specified users to achieve specified goals effectively, efficiently and with satisfaction in a specified context of use”.
If we go by this definition of usability, we can say that Accessibility is sort of special case of Usability –
· Accessibility stresses on including people with disabilities as “specified users”.
· Assistive technologies used by people with disabilities define and contributes to the “specified context of use” in accessibility design situations.
Because of this, it is possible to make accessibility goals part of the overall user-centered-design process and use the accessibility implementation techniques in addition to standard UCD techniques to develop usable and accessible web applications. But while it is true that there are significant overlaps, it is important to understand some important distinctions.
· Usability problems impact all users. They do not make distinction based on user ability. Disabled people do not feel extra severity of usability problem compared to able-bodied person just because they are disabled.
· Accessibility problems affect the ease of access to a web application by people with disabilities. When a disabled person is more at disadvantage relative to able-bodied person, the problem is clearly with accessibility.
The distinction is difficult to define when dealing with cognitive and language disabilities because many guidelines suggested for addressing these type of disabilities are actually as much applicable for design for general, able-bodied population.
There is also the point related to solving accessibility problems in a ‘usable way’. For example; specifying alt-texts is a necessary requirement for making use of images accessible. But if the alt-text is verbose or is written without keeping in mind the larger context of the web application, the accessibility guidelines may be satisfied but the solution is well short on the usability requirements.
Therefore, despite significant overlap, accessibility and usability problems must be identified as separate categories of issues and addressed accordingly. In specific situations like legal policy or compliance this distinction is very important. Having said this, it is important to keep in mind that the nuances of how usability and accessibility relate is of no consequence to most of web development which should aim at ensuring accessibility and usability for the largest user population.
Comments
Well said Chandan,
Accessibility and usability problems should be addressed separately.
Also concept of usable accessibility needs to be advocated than mere compliance to set of guidelines.
Posted by: Shrirang | December 10, 2008 11:44 AM
I agree with your opinion that Accessibility is sort of special case of Usability.
Do you know the online tools to check accessibility other than ATRC?
Posted by: dani | January 30, 2009 5:19 PM