Usability vs. Accessibility

Tags: Design
March 31, 2006 by Barbara

Usability refers to "ease of use". It is quantifiable on a number of scales. I frequently use "usability" to mean "quality of user experience", but that is a lazy shorthand.

Accessibility refers to the ability of different people to be able to use the application or web site. Can a blind user use the phone? (not a RAZR, she can't, probably not even to make a voice call). Can a hard of hearing user make a voice call? Can a vision impaired user use the web site with large font? Can a blind user use the site with a screen reader?

Accessibility is a bit more binary: can the blind user use the site? We can separately measure the usability of such access.

There are lots of tools and techniques for accessibility, and a lot of experts in the field, including Anitra Pavka.

What does this have to do with mobile? Quite a lot, actually.

First, mobile devices are in many ways like our differently abled users. The devices have differing capabilities, and the optimal design for each device depends in large part on the capabilities. Many accessibility experts, including both Anitra Pavka and Aaron Marcus already know this. These experts also know that accessibility and usability are not the same thing.

Unfortunately, mobile professionals do not understand the difference. Time and time again, "best practices" documents are published with an eye towards accessibility by all devices. These documents, in an effort to make application development as easy as possible, say how to make the application work on all devices.

The WAP Forum did this with their "General Content Authoring Guide" in 2000 that ignored all the usable aspects of the Openwave browser and some of the usable aspects of the Nokia browser. Sites were limited to links and a couple form elements only: no cache control, no navigation aids, nothing else.

The W3C did it again with the Mobile Web Best Practices document coming out of the mobile device working group. They have a token item saying "you should target devices", then the other 95% of the document is all about the least common denominator approach. (My style guide work has been included as a reference but it is clear that they did not bother with purchasing the document, which would have provided them with dozens more pages about specific techniques. They stuck with the free overview information. )

These approaches will ensure accessibility of information. They will not enable usability. Without device targeting with techniques like XSLT on the server, CSS on the device, using information about device interaction abilities not just technical abilities to target the design, you will end up with poor usability for all users, although they can actually access the information.

What would a desktop-only site look like without using various user targeting techniques such as CSS variants and alt text? For users using screen readers there would be a "skip navigation" link at the top of every screen. No graphic would contain text execpt perhaps the logo. For vision impaired users, all fonts would be very large. For color blind users high-contrast colors with a very limited color palette would be used, except where the information was redundant with the text. For hard-of-hearing users there would be no sounds. Flash would be very different. The experience would be limited for everybody.


«« Free Picture Mail from Sprint!  |  Fellow Travelers and Market Evolution »»

No Comments

No comments yet.

RSS feed for comments on this post.

Sorry, the comment form is closed at this time.