|
|
|
|
Computer accessibility
|
| |
|
| |
In human-computer interaction, computer accessibility (also known as Accessible computing) refers to the accessibility of a computer system to all people, regardless of disability or severity of impairment. It is largely a software concern; when software, hardware, or a combination of hardware and software, is used to enable use of a computer by a person with a disability or impairment, this is known as Assistive Technology.
There are numerous types of impairment that impact computer use.
Discussion
Ask a question about 'Computer accessibility' Start a new discussion about 'Computer accessibility' Answer questions from other users |
Encyclopedia
In human-computer interaction, computer accessibility (also known as Accessible computing) refers to the accessibility of a computer system to all people, regardless of disability or severity of impairment. It is largely a software concern; when software, hardware, or a combination of hardware and software, is used to enable use of a computer by a person with a disability or impairment, this is known as Assistive Technology.
There are numerous types of impairment that impact computer use. These include:
These impairments can present themselves with variable severity; they may be acquired from disease, trauma or may be congenital or degenerative in nature.
Accessibility is often abbreviated to the numeronym a11y, where the number 11 refers to the number of letters omitted. This parallels the abbreviations of internationalization and localization as i18n and l10n respectively.
Special needs assessment
People wishing to overcome an impairment in order to be able to use a computer comfortably and productively may need a "special needs assessment" by an assistive technology consultant (such as an occupational therapist or clinical scientist) to help them identify and configure appropriate assistive hardware and software. In the UK this may be provided by an NHS specialist centre such as Access to Communication and Technology in Birmingham http://www.actwmids.nhs.uk/
Where a disabled person is unable to leave their own home, it may be possible to assess them remotely using remote desktop software and a webcam. The assessor logs on to the client's computer via a broadband Internet connection. The assessor then remotely makes accessibility adjustments to the client's computer where necessary and is also able to observe how they use their computer.
Considerations for specific impairments
Cognitive impairments and illiteracy
The biggest challenge in computer accessibility is to make resources accessible to people with cognitive disabilities - particularly those with poor communication skills - and those without reading skills.
Their further development relies on public domain icons being available. Many people with a learning disability learn and rely on proprietary symbols. They thus become tied to particular products. The copyright owners are generally unwilling to release them on the web.
Other examples include Web accessibility a set of guidelines and two accessible web portals designed for people developing reading skills are peepo.com — try typing a letter with your keyboard for more — and peepo.co.uk with enhanced graphics, unique style controls and improved interactivity (requires an SVG supported browser).
Visual impairment
Another significant challenge in computer accessibility is to make software usable by people with visual impairment, since computer interfaces often solicit input visually and provide visual feedback in response. For individuals with mild to medium vision impairment, it is helpful to use large fonts, high DPI displays, high-contrast themes and icons supplemented with auditory feedback and screen magnifying software.
In the case of severe vision impairment such as blindness, screen reader software that provides feedback via text to speech or a refreshable braille display is a necessary accommodation for interaction with a computer.
About 8% of people, mostly males, suffer from some form of colour-blindness. In a well-designed user interface, colour should not be the only way of distinguishing between different pieces of information. However, the only colour combinations that matter are those that people with a deficiency might confuse, which generally means red and green and blue and green.
Motor and dexterity impairments
Some people may not be able to use a conventional input device, such as the mouse or the keyboard. Therefore it is important for software functions to be accessible using both devices; ideally, software uses a generic input API that permits the use even of highly specialized devices unheard of at the time of software development. Keyboard shortcuts and mouse gestures are ways to achieve this. More specialized solutions like on-screen software keyboards and alternate input devices like switches, joysticks and trackballs are also available. Speech recognition technology is also a compelling and suitable alternative to conventional keyboard and mouse input as it simply requires a commonly available audio headset.
The astrophysicist Stephen Hawking is a famous example of a person suffering from motor disability. He uses a switch, combined with special software, that allows him to control his wheelchair-mounted computer using his remaining small movement ability. This performs as a normal computer, allowing him to research and produce his written work, and as an Augmentative and Alternative Communication and environmental control device.
Hearing impairment
While sound user interfaces have a secondary role in common desktop computing, usually limited to system sounds as feedback, software producers take into account people who can't hear, either for personal disability, noisy environments, silence requirements or lack of sound hardware.
Such system sounds like beeps can be substituted or supplemented with visual notifications and captioned text (akin to closed captions).
Web accessibility
Enabling access to Web content for all users is the concern of the Web accessibility movement. Websites can be designed to be more accessible by their conformance to certain design principles.
Screen readers are of limited use when reading text from websites designed without consideration to accessibility; this can be due to the differences between spoken and written language and the complexity of text, but it is mainly due to poor page design practices. The tendency to indicate semantic meaning using methods that are purely presentational (e.g. larger or smaller font sizes, using different font colors, or images or multimedia to provide information) restricts meaningful access to some users. Therefore designing sites in accordance with Web accessibility principles helps enable meaningful access for all users.
For example, web designers can ensure that navigation and content is as plain and simple as appropriate and long texts should provide summaries.
Computer Software Restrictive Elements
These restrictive elements make utilization of a computer difficult for accessibility users:
Collapsing Menus
Software that incorporates Collapsing Menus has a facility that makes fundamental menu options not appear when the package menus are activated.
Instead a downward facing arrow appears at the bottom of the menu.
In order to access the missing menu options, it is necessary to activate the downward facing arrow. The menu will now change to include the missing options, and it is necessary to navigate the menu again to obtain the missing option. The problem reoccurs each time the menu is activated.
Problems
Problems with software incorporating this feature are:
The system requires more work for people who have difficulty in using the mouse or keyboard.
The downward facing arrow is difficult to activate with the mouse or the touchscreen.
The problem is recursive.
Right Click
A mouse with two buttons is required. Depression of the second mouse button provides an alternative function to a normal mouse click.
Problems
Problems with software incorporating this feature are:
The interface is not compatible with touchscreen based systems because touchscreen devices generally do not generally provide alternative finger recognition or rightclick facilities.
Inclusion of a second mouse button causes confusion for left and right-handed users on shared computers.
Users unable to use a mouse cannot access the rightclick functionality.
Double Click
Double Click is a facility that requires depression of the mouse button in rapid succession to obtain an alternative function to a normal mouse click.
Problems
Problems with software incorporating this feature are:
The double click is difficult to achieve for some mouse and touchscreen users.
Middle Click
Middle Click is a facility that requires a three button mouse or emulation that requires pressing both mouse buttons simultaneously.
Problems
Problems with software incorporating this feature are:
The interface is not compatible with touchscreen based systems because touchscreens do not generally provide alternative finger recognition or middleclick facilities.
Users unable to use a mouse cannot access the middleclick functionality.
Drag
A drag event can be achieved by:
- Moving the mouse or pointing device with a button pressed
- A finger or pointer being moved whilst in continuous contact with a touchscreen or tablet device.
- A joystick being moved whilst the button is continually depressed
- The aiming device being moved whilst the trigger is continually depressed
Problems
One of the problems with software incorporating this feature is that some users find interfaces requiring drag movements are difficult to use, particularly for accessibility users, or users with limited dexterity.
Neighbouring Widgets
Neighbouring Widgets is system design flaw built into some graphical user interfaces caused by placement of widgets in close proximity to each other.
Problems
This causes a problem for users that lack precision targeting skills with the mouse pointing device, or users that produce mouse jolt when they attempt to click a mouse button.
No Keyboard Equivalents
This is a system design flaw, whereby some functionality provided by mouse navigation is not replicated by a keyboard equivalent.
Problems
The problem with software containing this flaw is that users with limited dexterity will not be able to make use of the required functionality.
Examples of this include the lack of a facilities in Microsoft Word to Switch Between Headers and Footers, or to resize boxes and tables using only the keyboard.
No Joystick Equivalents
Some windowing systems do not allow the joystick to be used to control the pointer or cursor. This flaw makes the system difficult to operate by users with limited dexterity, because they cannot utilize the joystick for basic system operation.
Focus stealing is a facility built into some graphical user interfaces and windowing management systems that allows an application that is not in focus to suddenly gain focus and steal user input intended for the previously focused application.
Pop Up Boxes
See also
External links
- emphasising accessibility
- - contains guides on accessibility options and information about specialist assistive hardware and software
-
- for Microsoft Office
- - provides information on Accessibility, Assistive Technology and Remote Assessment
- Consortium For E-learning Accessibility
-
-
Accessibility features of Operating Systems
Web browser accessibility features
Software platform accessibility features
Live forums
- [irc://irc.freenode.net/#accessibility Chat] with experts on internet accessibility
|
| |
|
|
