Accessibility: the benefits and challenges of Web 2.0

Mouse-less access

WCAG says that all functions and information should be available without using a pointing device such as a mouse. This is essential for blind users (who cannot point) but is also required by some users with muscular-skeletal impairments such as RSI or missing upper limbs. These users control the computer by a limited number of short-cut keys or switches; pointing is very difficult with these input devices.

Visualisation technology needs to be built so that all its functions can be accessed without a pointing device. For example simple controls such as zoom-in must be accessible via menus and short-cut keys. Further, any object in the visualisation, for example a process box in a business flow diagram, should be accessible via alternative techniques. Possible techniques include:

• A separate pane with a list of the objects that can be chosen.
• A say-what-you-see function, which enables a user to speak or type the name of the object and for it to be highlighted.
• A tab function that jumps from one object to the next.

Screen-readers

Finally, let me discuss visualisation and users who are blind and depend on screen-reader technology. How can the information that has been visualised be supplied in a form that a screen-reader can process it?

Dashboards basically visualise tables of information so the screen-reader should be presented with well marked-up tables, any information that is highlighted in the visualisation (e.g. a traffic light that has gone red) should be available in a separate section that can easily be navigated to, for example by having a section with a header of ‘highlights’.

Diagrams, such as business flow diagrams, should provide lists of the objects in the diagram and for each one, on request, further details. The details should include the type, name, description, position and a list of links to other objects. With this type of information the user will be able to navigate around the diagram and develop a mental image of the diagram or more precisely an understanding of the concept the diagram attempts to portray.

Maps and other spatial representations are the most difficult to support. The question that needs to be answered is what information would a blind person want from such technology. My understanding is that this would include:

• How do I get from A to B?
• What is the nearest station, coffee shop, bank to B?
• What countries border C?
• Which towns does River R flow through?

All of this information needs to be provided in a structured text format that the screen-reader can navigate like a document.

Technology

Most of the functionality I have described above has to be provided by the visualisation technology rather than by the webmasters. I will be reviewing suppliers of visualisation software during the summer.

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