In Section 5.1 you assessed the usability of Figure 11, the noticeboard in a public park. For a visually impaired person, that noticeboard might not be usable at all, as you may have commented. This raises the issue of accessibility. Accessibility relates to how well a service is adapted to the diverse abilities of all potential users. Disabled people and people with various kinds of impairment have an interest in accessibility, but accessibility is not exclusively concerned with their needs. For example, users of online services might be using mobile phones or PDAs (personal digital assistants) to access the services, or might have slow connection speeds. If people have difficulties using the services because of their equipment, then they have accessibility problems. Accessibility therefore overlaps to some degree with usability.
Activity 27 (Exploratory)
How might a web designer cater for users with slow connections?
One of the most useful ways of catering for users with slow connections is minimising the total size of files that are downloaded when web pages are accessed. Large files take a long time to download and therefore cause delay. The solution is usually to avoid large graphics files, sound files or video files. Sometimes a text-only version should be offered.
Generally designers want their sites to be usable and accessible by all users, in so far as that is feasible. In the UK, at the time of writing, there is also a legal dimension: disabled people have a strong legal case if they can show that failure to take account of their needs has disadvantaged them.
Some of the features required for good accessibility are easy to envisage. For instance, some users need to be able to adjust font sizes, screen resolution, and so on. Other users might find particular combinations of foreground and background colour make text hard to read. However, the accessibility implications of other features of interfaces are not so readily apparent. Some users, for instance, have a screen reader, which uses a synthesised voice to read on-screen text aloud. Other users have a speech-driven web browser, in which commands are spoken into a microphone. These are examples of adaptive technology or assistive technology, and the design of a website can considerably help or hinder their use. For example, many web pages have a panel on the left or at the top with links to other parts of the site. The sighted user can easily ignore these if they are of no interest. Screen readers, however, often begin by reading out these links. This can be useful on the first visit to a site, but on subsequent visits it can be frustrating for the user to have to endure the same recitation of links. A 'skip navigation' link or button right at the start of the page allows the user of a screen reader to skip this part of the page. In an accessible design, this 'skip navigation' facility can be invisible to a sighted user, but so placed that it is the first thing read by a screen reader.
For people who use a keyboard rather than a mouse, navigation is made easier if there are access keys. These are more-or-less standard keyboard shortcuts that can be incorporated into web pages. For instance, Alt 1 generally jumps to the homepage, Alt 4 jumps to a search facility. Alt 2 is generally a 'skip navigation' link, taking the user straight to the main content of a page.
Activity 28 (exploratory)
There are some optional accessibility features built into Windows, and you should spend a few minutes investigating them. If you go to the Control Panel (reached from the Start button, and possibly then via 'Settings'), you should see an icon labelled 'Accessibility Options'. These give you options relating mainly to your mouse and keyboard. If there is an option 'Configure Windows to work for your vision, hearing and mobility needs', note this will launch a 'wizard' that allows you to change your settings. If you are concerned that you might not be able to undo any changes, be sure not to select any modifications that are offered.
Depending on your version of Windows, you may find further accessibility tools if you go to the Windows Start button, choose 'Programs', select 'Accessories', and then select 'Accessibility'.
When I looked at these I was struck that the options available were quite modest: changes in text size in menus and dialogue boxes, the option to drive the cursor using the keypad rather than a mouse, and so on. I was interested to see that 'sticky keys' allows keys that sometimes have to be pressed simultaneously with other keys (mainly shift-, control- and alt-) to be pressed in sequence. I was very surprised that no single action can be used as a substitute for double-clicking.
Figures 12 and 13 show an example of an accessibility tool, developed in New Zealand. The Lomak ('light operated Mouse and Keyboard') replaces a standard computer keyboard and mouse. The user directs a light source at the keyboard to get standard keyboard and mouse functions. The light source can be worn on the head or be hand-held.
Further information on accessibility aids can be found by searching the Web with terms such as 'adaptive technology', 'accessibility aids' and 'accessibility software'.