GPII.eu Common Terms

The table on this page describes so-called “common terms” defined for the Global Public Inclusive Infrastructure (GPII). “Common” means that these terms can apply across applications and devices, as opposed to “application-specific terms”, which apply to a specific application (or operating system). “Common” also implies that not all of these terms were defined specifically with the Web in mind. For example, cursorSize can be set on some operating systems but not by means of CSS styles.

Not all common terms are relevant to every type of GPII implementation. For example, several operating systems have built-in screen magnifiers and screen readers, and support various cursor sizes. Web browsers and web applications typically don't. As a consequence, common terms such as magnifierEnabled, screenReaderTTSEnabled and cursorSize can often be mapped to operating system settings, but not to features in browsers or web applications.

All “common terms” reside in the namespace http://terms.gpii.eu/common; in order to save space, this namespace is not mentioned in the table below. The expanded name of a term includes the namespace, for example http://terms.gpii.eu/common/highContrastEnabled.
(People who are familiar with GPII or the EU-funded project Cloud4all should be aware that the namespace differs from the “official” namespace http://registry.gpii.net/common. In addition, the gpii.eu namespace was changed from http://registry.gpii.eu/common to http://terms.gpii.eu/common in May 2019.)

Default values are purely informative since it would be inappropriate for GPII to tell applications what default value they should use. The default values mentioned in the table are based on what applications use most as a default value.

Table with selected “common terms” defined in GPII
Identifier Application type Data type Value range Default value Description
highContrastEnabled Screen enhancement Boolean true / false false Determines whether a high-contrast theme should be enabled.
highContrastTheme Screen enhancement String black-white, white-black, yellow-black, black-yellow, lime-black black-white The high-contrast theme. The chosen theme only becomes active when highContrastEnabled is set to True.
cursorSize Screen enhancement Float 0.0 .. 1.0 0.5 Cursor size. (Operating systems such Microsoft Windows and GNU/Linux deskstops such as GNOME support various cursor sizes. Browsers or web content cannot override this.)
mouseTrailing Screen enhancement String 0 .. 10 no default Length of the mouse trail. The maximum value for Windows 7 is probably 6.
linkAdaptation Screen enhancement String default, emphasizeLinks, hideLinks, disableLinks, removeLinks, annotateLinks default How links should be adapted. hideLinks: change their colour to that of normal text. disableLinks: disable link anchors, so they can no longer be traversed. removeLinks: remove link anchors. annotateLinks: augment the link with comments.
colourSaturation Screen enhancement Integer 1 .. 100 (minimum – maximum saturation) no default Determines the colour saturation on a screen (hardware).
sharpness Screen enhancement Integer 1 .. 100 (minimum – maximum saturation) no default Determines the sharpness on a screen (hardware).
contrast Screen enhancement Integer 1 .. 100 (minimum – maximum saturation) no default Determines the contrast on a screen (hardware).
magnifierEnabled Screen magnification Boolean true / false false Determines whether a screen magnifier should be turned on.
magnification Screen magnification Float 1.0 .. * 1 The magnification level. The value 1 means no magnification.
tracking Screen magnification array of Strings one or more of: mouse, caret, focus mouse How objects on the screen should be brought into the focus of the magnifier. mouse: follow the mouse cursor. caret: follow the edit cursor. focus: follow keyboard focus. These values can be combined.
magnifierPosition Screen magnification String FullScreen, Lens, LeftHalf, RightHalf, TopHalf, BottomHalf, Custom TopHalf Where the magnifier should be positioned on the screen.
invertColours Screen magnification Boolean true / false false Inverts the colours on the screen. This should not be confused with a light on dark contrast theme. While contrast themes enhance contrast, colour inversion is often used to get rid of an overwhelming white background.
showCrosshairs Screen magnification Boolean true / false false Determines whether the normal mouse pointer should be replaced by (or enhanced with) crosshairs to make the current mouse position easier to sea.
captionsEnabled Alternatives and augmentations for media or text Boolean true / false false Determines whether capions (or “subtitles for the Deaf or hard of hearing” should be turned on. Captions should not be confused with “normal” subtitles, which merely translate the spoken content of a video. Captions also describe important non-speech sounds.
subtitlesEnabled Alternatives and augmentations for media or text Boolean true / false false Determines whether subtitles should be turned on.
audioDescriptionEnabled Alternatives and augmentations for media or text Boolean true / false false Determines whether audio description should be turned on. (This is sometimes done by providing an alternative video that has audio description.)
signLanguageEnabled Alternatives and augmentations for media or text Boolean true / false false Determines whether sign language should be provided or turned on.
signLanguage Alternatives and augmentations for media or text String Language tags conforming to IETF BCP 47. no default Language tag identifying a sign language. Examples: ase: American Sign Language; asf: Australian Sign Language; bfi: British Sign Language; csl: Chinese Sign Language; fsl: French Sign Language; gsg: German Sign Language; rsl: Russian Sign Language; ssp: Spanish Sign Language.
signLanguageInterpreterType Alternatives and augmentations for media or text String human, avatar no default Determines whether (videos of) a human sign language interpreter or a sign language avatar should be used.
pictogramsEnabled Alternatives and augmentations for media or text Boolean true / false false Determins whether pictograms should be added to support people with a reading disability or a general learning disability (UK) / intellectual disability (ID) (USA).
pictogramsSymbolSet Alternatives and augmentations for media or text String ARASAAC, Bliss, Wahl no default Determines which symbol set should be used. See for example ARASAAC and Bliss.
simplifiedUiEnabled Cognitive support Boolean true / false false Determines whether the application should provide a simplified user inteface, especially for people with a general learning disability (UK) / intellectual disability (ID) (USA).
onScreenKeyboardEnabled Input Boolean true / false false Determines whether the on-screen keyboard should be activated. This is mainly for operating systems and applications that don't automatically activate an on-screen keyboard when text input is required.
voiceControlEnabled Input Boolean true / false false Determines whether speech recognition for input (including access to user interface elements) should be enabled.
fontSize Text formatting Float 0.1 .. * (in points) 12 Font size in points. Note that CSS can describe font-size using various types of values. See also, for example, CSS Font-Size: em vs. px vs. pt vs. percent.
lineHeight Text formatting (String) The values for line-height in CSS 2.1, except the value inherit. normal (the default value in CSS 2.1) See line-height in CSS 2.1. Note: CSS 3 is still under development. The latest version of the CSS specification is the CSS Snapshot 2017.
foregroundColour Text formatting (String) See the values for colour units in CSS 3. no default Determines the text colour.
backgroundColour Text formatting (String) See the values for colour units in CSS 3. no default Determines the background colour.
unvisitedLinkColour Navigation (String) See the values for colour units in CSS 3. no default Determines the colour of unvisited links.
visitedLinkColour Navigation (String) See the values for colour units in CSS 3. no default Determines the colour of visited links.
focusedLinkColour Navigation (String) See the values for colour units in CSS 3. no default Determines the colour of links when they receive focus. Note: In CSS 3, this corresponds with :focus.
displaySkiplinks Navigation String one of: always, onfocus, never no default Determines the visibility of skiplinks: always visible, only on keyboard focus (and possibly on hover), or never.
tableOfContents Navigation Boolean true / false false Determines whether a table of contents should be displayed, possibly generated from the heading structure in the document.
autoTabbingEnabled Forms and other input elements Boolean true / false false Determines whether keyboard focus should automatically move to the next input field in a set of related fields (e.g. when inputting a phone number requires a series of fields). For keyboard users, this can disrupt the normal behaviour model for interaction with forms. (Background: Jim Allan: Re: Auto-Tabbing - Is this ever allowed?, WAI Interest Group, 28 May 2015.)
autoFormFocusEnabled Forms and other input elements Boolean true / false false Determines whether keyboard focus should automatically jump to a form field (typically the first form field on a page) when a page is loaded in a browser. Since such behaviour skips page elements such as the site navigation and form filling instructions, it decreases the usability of a page for screen reader users and other keyboard users. (Background: Jim Allan: Re: Auto-Tabbing - Is this ever allowed?, WAI Interest Group, 28 May 2015.)
sessionTimeout Timeouts Integer 1 .. * (in seconds) no default Determines how many seconds a user can remain inactive before a session times out. People with certain specific disabilities need longer session timeouts. See for example Understanding SC 2.2.1 in Understanding WCAG 2.0.
screenLockTimeout Timeouts Integer 1 .. * (in seconds) no default
screenDimTimeout Timeouts Integer 1 .. * (in seconds) no default
selfVoicingEnabled Self-voicing applications Boolean true / false false Determines whether an application's self-voicing feature should be enabled.
language General settings String Language tags conforming to IETF BCP 47. no default The language of the application's user interface or the content.
speechRate Screen reader Integer 1 .. * (words per minute) 150 How fast the screen reader should speak; speed is defined in words per minute. Many screen readers don't express speech rate in words per minute, so the value for the common term will need to be converted. Note that some screen readers expect an integer and some versions crashed when give a floating point value.
trackingTTS Screen reader array of Strings one or more of: mouse, caret, focus focus How the screen reader should track what the user wants to be read. mouse: follow the mouse cursor. caret: follow the edit cursor. focus: follow keyboard focus. These values can be combined.
speakTutorialMessages Screen reader Boolean true / false false Determines whether the screen reader should read as object in the interface received focus, for example, how to interact with the currently focused object.
This common term is based on “Enable Tutorial Messages” in Orca. Note: Not to be confused with reporting tooltips or object descriptions.
keyEcho Screen reader Boolean true / false true Determines whether the screen reader should speak or “echo” each character typed by the user.
wordEcho Screen reader Boolean true / false false Determines whether the screen reader should speak or “echo” each word typed by the user. wordEcho and keyEcho are not mutually exclusive.
announceCapitals Screen reader Boolean true / false false Determines whether the screen reader should in some way announce that a letter is a capital. For example, NVDA can be set to say “cap” for capitals.
screenReaderBrailleOutput Screen reader Boolean true / false false Determines whether the screen reader's Braille output should be enabled. screenReaderBrailleOutput is not mutually exclusive with screenReaderTTSEnabled.
punctuationVerbosity Screen reader String One of the following values: none, some, most, all some Determines the level of detail the screen reader should use when encountering punctuation marks. none: no punctuation marks are read aloud. some: some punctuation marks are read aloud. most: most punctuation marks are read aloud. all: all punctuation marks are read aloud.
readingUnit Screen reader String One of the following values: word, line, sentence, paragraph sentence
auditoryOutLanguage Screen reader String Language tags conforming to IETF BCP 47. no default Determines the text-to-speech language used by the screen reader. (This should not prevent live switching to other languages based on language switches identified inside documents.)
screenReaderTTSEnabled Screen reader Boolean true / false false Determines whether synthetic speech should be enabled in the screen reader. screenReaderTTSEnabled is not mutually exclusive with screenReaderBrailleOutput.
pitch Screen reader Float 0.0 .. 1.0 0.5 Determines the pitch for the screen reader's synthetic speech.
volumeTTS Screen reader Float 0.0 .. 1.0 no default Determines the volume for the screen reader's synthetic speech.
hapticFeedback Touch screen (mobile device) String none / always none Enables vibration. (Note: iOS 7 supports at least 3 options: silent mode, vibrate mode and vibrate on particular interactions.)
screenOffTime Touch screen (mobile device) Integer 0 .. * (seconds) 30 The time in seconds before the screen is dimmed.
screenDimEnabled Touch screen (mobile device) Boolean true / false true
screenRotationEnabled Touch screen (mobile device) Boolean true / false true
screenDefaultRotation Touch screen (mobile device) Integer 0, 1, 2, 3 1 The numbers map to the following rotations: 0 = 0°; 1 = 90°; 2 = 180°; 3 = 270°;
screenLockTimeout Touch screen (mobile device) Integer 1 .. * (seconds) no default
screenDimTimeout Touch screen (mobile device) Integer 1 .. * (seconds) no default
alertsEnabled Touch screen (mobile device) Boolean true / false no default
Identifier Application type Data type Value range Default value Description

Notes related to implementation in JSON: