While some terms are defined in place, the following definitions are used throughout this document.
Operating systems and other platforms provide a set of interfaces that expose information about objects and events to assistive technologies. Assistive technologies use these interfaces to get information about and interact with those widgets. Examples of this are the Java Accessibility API [JAPI], Microsoft Active Accessibility [MSAA], the Mac OS X Accessibility Protocol [AXAPI], the Gnome Accessibility Toolkit (ATK) [ATK], and IAccessible2 [IA2].
The accessible name is the name of a user interface element. Each platform accessibility API provides the accessible name property. The value of the accessible name may be derived from a visible (e.g., the visible text on a button) or invisible (e.g., the text alternative that describes an icon) property of the user interface element.
A simple use for the accessible name property may be illustrated by an "OK" button. The text "OK" is the accessible name. When the button receives focus, assistive technologies may concatenate the platform's role description with the accessible name. For example, a screen reader may speak "push-button OK" or "OK button". The order of concatenation and specifics of the role description (e.g. "button", "push-button", "clickable button") are determined by platform accessibility APIs or assistive technologies.
Hardware and/or software that acts as a user agent, or along with a mainstream user agent, to meet the interface requirements of users with disabilities beyond those offered by the mainstream user agents.
Services provided by assistive technologies include alternative presentations (e.g., synthesized speech or magnified content), alternative input methods (e.g., speech recognition), additional navigation or orientation mechanisms, and content transformations.
Assistive technologies often communicate with mainstream user agents by using and monitoring accessibility APIs.
The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities, whereas assistive technologies usually target users with specific disabilities. The assistance provided by assistive technologies is more specific and appropriate to the needs of its target users.
Examples of assistive technologies that are important in the context of this document include the following:
In this specification, attribute is used as it is in markup languages. Attributes are structural features added to elements to provide information about the states and properties of the object represented by the element.
An set of instance objects that share similar characteristics.
In this specification, element is used as it is in markup languages. Elements are the structural elements in markup language that contains the data profile for objects.
A programmatic message used to communicate discrete changes in the state of an object to other objects in a computational system. User input to a web page is commonly mediated through abstract events that describe the interaction and can provide notice of changes to the state of a document object. In some programming languages, events are more commonly known as notifications.
Indicates that the element is not visible or perceivable to any user. An element is only considered hidden in the DOM if it or one of its ancestor elements has the aria-hidden attribute set to true.
Note: Authors are reminded that visibility:hidden and display:none apply to all CSS media types; therefore, use of either will hide the content from assistive technologies that access the DOM through a rendering engine. However, in order to support assistive technologies that access the DOM directly, or other authoring techniques to visibly hide content (for example, opacity or off-screen positioning), authors need to ensure the aria-hidden attribute is always updated accordingly when an element is shown or hidden.
Content provided for information purposes and not required for conformance. Content required for conformance is referred to as normative.
Accessible to a user using a keyboard or assistive technologies that mimic keyboard input, such as a sip and puff tube. References in this document relate to WCAG 2 Guideline 2.1; "Make all functionality available from a keyboard" [WCAG20].
A type of region on a page to which a user may want quick access. Content in such a region is different from that of other regions on the page and relevant to a specific user purpose, such as navigating, searching, perusing the primary content, etc.
Live regions are perceivable regions of a web page that are typically updated as a result of an external event when user focus may be elsewhere. These regions are not always updated as result of a user interaction. This practices has become common place with the growing use of Ajax. Examples of live regions are a chat log, stock ticker, or a sport scoring section that updates periodically to reflect game statistics. Since these asynchronous areas are expected to update outside the user's area of focus, assistive technologies such as screen readers have either been unaware of their existence or unable to process them for the user. WAI-ARIA has provided a collection of properties that allow the author to identify these live regions and how to process them: aria-live, aria-relevant, aria-atomic, and aria-busy. Pre-defined live region roles are listed in the Choosing Between Special Case Live Regions ([ARIA-PRACTICES], Section 5.3).
A state that is relevant to accessibility APIs but whose value is read and set by the user agent. The application author does not always manage these states, but needs to be aware that the user agent will. In some cases the application author does manage these states as well. Common managed states include focus and selection.
Required for conformance. By contrast, content identified as informative or "non-normative" is not required for conformance.
A "thing" in the perceptual user experience, represented in markup languages by one or more elements, and rendered by user agents. Objects are instances of classes, which define the general characteristics of similar objects. A single DOM element may or may not correspond with a single object in an accessibility API. An object in an accessibility API may encapsulate one or more DOM elements.
A description of the characteristics of classes and how they relate to each other.
Usable by users in ways they can control. References in this document relate to WCAG 2 Principle 2; content must be operable [WCAG20]. See Keyboard Accessible.
An 'owned element' is any DOM descendant of the element, any element specified as a child via aria-owns, or any DOM descendant of the owned child.
Presentable to users in ways they can sense. References in this document relate to WCAG 2 Principle 1; content must be perceivable [WCAG20].
Attributes that are essential to the nature of a given object, or that represent a data value associated with the object. Certain properties (for example, aria-multiline) are less likely to change than states or properties that represent a data value (for example, aria-valuenow); a change of a property may significantly impact the meaning or presentation of an object. See clarification of states versus properties.
A connection between two distinct, articulable things. Relationships may be of various types to indicate which object labels another, controls another, etc.
Main indicator of type. This semantic association allows tools to present and support interaction with the object in a manner that is consistent with user expectations about other objects of that type.
The meaning of something as understood by a human, defined in a way that computers can process a representation of an object, such as elements and attributes, and reliably represent the object in a way that various humans will achieve a mutually consistent understanding of the object.
A state is a dynamic property expressing characteristics of an object that may change in response to user action or automated processes. States do not affect the essential nature of the object, but represent data associated with the object or user interaction possibilities. See clarification of states versus properties.
A hierarchical definition of how the characteristics of various classes relate to each other, in which classes inherit the properties of superclasses in the hierarchy. A taxonomy can comprise part of the formal definition of an ontology.
Presentable to users in ways they can construct an appropriate meaning. References in this document relate to WCAG 2 Principle 3; Information and the operation of user interface must be understandable [WCAG20].
Any software that retrieves and renders web content for users, such as web browsers, media players, plug-ins, and other programs including assistive technologies.
A literal that solidifies the information expressed by a state, property, role, or text content.
Discrete user interface object with which the user can interact. Widgets range from simple objects that have one value or operation (e.g., check boxes and menu items), to complex objects that contain many managed sub-objects (e.g., trees and grids).