Terminology for Accessibility and Assistive Technology
Terminology for Accessibility and Assistive Technology
June 2007 http://www.becta.org.uk page 1 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
Contents
Introduction
A – Z listing
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P
| Q | R | S | T | U | V | W | X | Y | Z
June 2007 http://www.becta.org.uk page 2 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
Introduction
In promoting the accessibility of software and developing common standards, it is clearly important that developers, practitioners and users share a common terminology to describe the features and functionality of software.
This proposed common ‘language of accessibility’ was developed through consultation and is intended for use by developers, intermediaries and end-users. It lists accessibility techniques, options and parameters based on current use.
As with other forms of technology, assistive technology is constantly changing. If you have comments or additions to make to the terminology, please send them to [email protected].
A-Z listing
AAC
Augmentative and Alternative Communication. The practice and science of creating and using communication systems for people with impaired language skills or for those who have physical difficulties with writing or speaking.
acceleration
A setting for controlling the mouse pointer more accurately, while still being able to move large distances easily. The speed of the pointer is increased by a set factor - for example if the acceleration is set to 2, then moving the mouse 2 times faster increases the mouse speed by a factor of 4.
accelerator keys
Accelerator keys are single key presses that take you to items in a menu that has already been opened with a mouse click or keyboard shortcut.
acceptance
The registration by the system that a valid switch, button or key press has been made following filtering.
acceptance delay
The time a switch or key has to be held down before the system responds; also known as ‘hold down time’.
June 2007 http://www.becta.org.uk page 3 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
accessible
A system or service that allows users using a variety of control methods to gain access to, control and use it can be considered accessible; this may not imply that the access is efficient (or usable) for all users. analogue joystick
With this, the cursor/selection speed varies with deflection of the joystick. A games joystick is an analogue device. assistive technology
Any technology that can enable a user to perform a task which they have difficulty with because of a disability. auto restart
A setting for a scanning system to reset the current highlight back to the start position of the scan, rather than carrying on to the next item. autoscan
A scanning process where the timing of the scan is pre-set rather than under the direct control of the user.
Probably the most popular and most efficient system for users with good timing. Not frequently used for two switch users but possibly should be considered more frequently. Two switch autoscan can speed up access and can be a bridge to single switch usage. See also scanning, critical overscan. chord keyboard
A keyboard where a small number of keys are held down in different patterns simultaneously to produce characters, like playing a chord on a piano). communication aid
An assistive technology device that can augment a user's communication; many of these are electronic devices incorporating artificial or recorded voice output. continuous
The property of a device or system to be controlled in one or more dimensions without sudden steps or jumps.
June 2007 http://www.becta.org.uk page 4 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
contrast
The difference in hue or more usually luminance (brightness) between an object (usually text) and its background.
critical overscan
A form of autoscan where the scan initially moves very fast and then does a slow reverse scan to combine speed with accurate selection. It is a way of giving users with poorer control of timing faster access to larger grids with less effort; see also scanning, autoscan.
debounce
A way of removing unwanted switch signals caused by poor electrical contacts in the switch itself or a tremor of the user; also known as tremor delay. There is a subtle difference between debounce and post-acceptance delay.
dimension
The number of degrees of freedom of control that a device has.
directed scan
With this, the user controls the direction and then extent of the scan to arrive at an item, so it is a way for single-switch users to control their own movement over a large number of options at one level.
dwell select
The process of having items in a selection set or grid chosen by pointing at an item or cell for a set time. It can also be used by people who use a pointing device but cannot click; in this case, holding the pointer within a small area for a set time automatically causes a click.
element
A single user interface item that contains information or a control.
emulator
An assistive technology software or hardware device that can replace the standard keyboard, mouse or other device.
end user
The person who uses the technology to perform a task.
June 2007 http://www.becta.org.uk page 5 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
event
The signal that something has happened, such as switch down (pressed) or switch up (released).
eye gaze
Systems that translate movement of a person’s eye into screen pointer movement.
filter, filtering
A utility or hardware device that removes unwanted actions that may be caused by user errors or disabilities; common filters include tremor delay, post-acceptance delay.
filter keys
A utility that adds timed responses to keyboard input to remove errors caused by tremors or poor motor control.
font
This is the full description of the appearance of text which should include font size and typeface. It is commonly used incorrectly as an equivalent of typeface.
font colour
The colour of text on the screen.
font size
The size of text on the screen or print, measured in points. The minimum recommended print size is 12 point. The actual size on the screen will depend on the size of the screen as well.
Graphical User Interface (GUI)
A user interface controlled from visible objects on the screen consisting of windows, buttons and icons intended for access with a mouse.
grid
A rectilinear selection set of items arranged in rows and columns, for selection by the user; scanning may be carried out by simple scanning, row/column or column/row.
head pointers
Systems which interpret head movement and move the screen pointer appropriately.
hue
June 2007 http://www.becta.org.uk page 6 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
A measure of the colour in terms of its red, green and blue components.
icon
An image often containing a control or link.
interface
This has two uses:
The way a user interacts with a computer or other device (as in, for example, Graphical User Interface).
A hardware device that allows two devices to be connected together (as in a switch interface).
item
A single selectable element of user interface; the item that contains the text or command to be acted upon when selected.
joystick
Devices that can control computer screen pointers, games or wheelchairs by moving a stick from its rest position.
key
A single switch in an array (keyboard) sending a single character, or in the case of modifier key, changing the action of other keys; see also modifier keys.
keyboard
An array of switches which can be programmed to send characters, words or controls to a system.
keyboard emulator
A device or program that replaces or parallels the functionality of the keyboard with an alternative.
keyboard shortcut
A key or combination of keys which replaces the graphical/mouse access to a control; for example, control + P will print a document in Windows.
June 2007 http://www.becta.org.uk page 7 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
layered hierarchy
A way of arranging large numbers of items in groups and sub-groups so that they can be accessed more quickly or with less effort.
luminance
The brightness of an object or area on the screen.
membrane keyboard
A flat, featureless keyboard that can be programmed with letters, words and controls as a supplement to or replacement of, the standard keyboard.
modifier keys
A key such as the control, alt, shift, or command (clover) keys which modify the action of other keys when used in combination with them.
mouse emulator
A software or hardware device that can replace or supplement the standard mouse.
mouse keys
An accessibility option that allows the mouse pointer to be controlled from a numeric key pad or other keys.
mouse speed
The relation between the speed of mouse movement and the movement of the pointer on the screen.
on-screen keyboards
Virtual keyboards that appear on computer screens and have the same function of physical keyboards; some can be accessed with the screen pointer and others with switches, or both.
pointer
The on-screen indicator of the mouse action point or a device that can move that point.
pointing device
A device such as a mouse, joystick, trackball, head pointer or eye gaze that can move a pointer relatively on a screen.
June 2007 http://www.becta.org.uk page 8 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
port
A connection point for input and output to and from a computer or other electronic device.
post-acceptance delay
A specified time following an event such as a switch press in which all further events are ignored; see also debounce, tremor delay.
press
The ‘switch down’ event.
register
An event is registered when it has been accepted by a system.
release
The switch or key up event.
repeat delay
The time between a key press (for example) being accepted and the start of the repetition of the key action being repeated
repeat time
The time between key repeats following the repeat delay; this is a preferred term to repeat rate.
SAPI (Speech Application Programming Interface)
The Microsoft speech system that implements text-to-speech in software.
scan
The movement of the highlight from one item to the next; this will either happen at pre-set times or following a scan switch press being accepted.
scan reset
A setting where the highlight of a scanned selection set is returned to the initial item; this is commonly the top row, leftmost column or the top-left item.
June 2007 http://www.becta.org.uk page 9 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
scanning
The process of passing a highlight from one item or group of items to the next; commands or controls are then activated by selecting the current highlighted item with a switch. scanning method
The way in which a scan moves by the process of highlighting across a selection set so that choices can be made. selection set
A complete set of items and/or groups of items that are presented to the user for selection at any one time; some of the groups or items may be hidden until required. serial keys
A computer system utility that can receive information and commands from an external device such as a communication aid via a serial port. single-step scan
The most frequently used two-switch scanning method, this gives control to the user and takes away the pressure for the need to 'get it right'. slow keys
The Accessibility option for filtering out unwanted accidental key presses by delaying the keyboard response to key presses; see also filter keys, acceptance. speech recognition
A system where a user's speech is translated into text and commands; also known as voice recognition standard
An agreed set of rules or design criteria sticky keys
A modification of the keyboard that allows a sequential alternative to having to hold two keys at the same time, for example Control followed by P for print, rather than having to press these two keys at the same time. switch interface
A device for connecting switches to a computer port.
June 2007 http://www.becta.org.uk page 10 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
switched joystick
With this, the cursor/selection speed is constant when the stick is pressed in a limited number of directions – usually 4 or 8. The system being controlled can act continuously or with a single action each time the joystick is pressed. tablet computer
A computer that uses a touchscreen or pen rather than a standard keyboard and mouse. These are now widely used as communication aids. text-to-speech
The process of taking text and converting it to audible speech. toggle
A switch or other control that is activated (that is, pressed) once for on, then again for off. toggle keys
A modification of the keyboard that allows a modifier key to be held down and released by a sequential action. For example, the shift key can be held down by pressing it twice, capital letters entered and then released by hitting the shift key again. touchscreen
A way of directly moving the pointer and clicking by touching a screen. There are four main types:
Resistive: these can be operated with the flat of a finger
Capacitive: these need a sharp point to move the pointer, such as a finger nail
Active Pen: these need a compatible electronic pen to move the pointer
Infra-red: with these, infra-red beams covering the screen are interrupted by fingers, hands or other pointers, and no actual contact is needed. trackball
A mouse pointer controller that uses a ball to move the mouse pointer when the ball is rolled in a given direction. typeface
The shape of a set a letters, eg Arial, Times New Roman.
June 2007 http://www.becta.org.uk page 11 of 12 © Becta 2007 Becta | Terminology for Accessibility and Assistive Technology
usability
Linked with accessibility, this is a measure of the usefulness of the user interface for assistive technology users.
USB
The Universal Serial Bus. A port now fitted to all computers, both PC and Mac. user scan
Similar to autoscan, this gives more control to the user as the scan proceeds as long as a switch is help down. It can be useful for those whose release is more controlled than their press. valuator
A device such as a mouse, joystick, trackball, head pointer or eye gaze that can move a pointer relatively on a screen.
June 2007 http://www.becta.org.uk page 12 of 12 © Becta 2007