Graphics Accessibility API Mappings

W3C Editor's Draft

This version:
https://w3c.github.io/graphics-aam/
Latest published version:
https://www.w3.org/TR/graphics-aam-1.0/
Latest editor's draft:
https://w3c.github.io/graphics-aam/
Editors:
(Igalia, S.L.)
(W3C)
Former editors:
(IBM Corporation) (until September 2016)
(Knowbility) (until August 2017)
Authors:
(IBM Corporation)
(Knowbility)
(W3C)
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GitHub w3c/graphics-aam
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Abstract

The Graphics Accessibility API Mappings defines how user agents map the WAI-ARIA Graphics Module [GRAPHICS-ARIA-1.0] markup to platform accessibility APIs. It is intended for user agent developers responsible for accessibility in their user agent so that they can support the accessibility of graphics such as that created for [SVG] or [HTML52].

The implementation of this specification in user agents enables authors to produce more accessible graphics by conveying common graphics semantics to assistive technologies. It provides Accessibility API Mapping guidance for the roles defined in the WAI-ARIA Graphics Module [GRAPHICS-ARIA-1.0].

The Graphics Accessibility API Mappings is part of the WAI-ARIA suite described in the WAI-ARIA Overview.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This is an Editor's Draft of Graphics Accessibility API Mappings 1.0 by the SVG Accessibility Task Force, a joint task force of the Accessible Rich Internet Applications Working Group and the SVG Working Group. It provides guidance for mapping roles in WAI-ARIA Graphics Module [GRAPHICS-ARIA-1.0] to accessibility APIs, and complements SVG-specific mappings in the SVG Accessibility API Mappings [SVG-AAM-1.0]. It extends Core Accessibility Mappings 1.1 [CORE-AAM-1.1], and is part of a suite of similar technology-specific Accessibility API Mappings specifications.

Feedback on any aspect of the specification is accepted. For this publication, the SVG Accessibility Task Force particularly seeks feedback on the following questions:

To comment, file an issue in the W3C graphics-aam GitHub repository. If this is not feasible, send email to public-aria@w3.org (comment archive). In-progress updates to the document may be viewed in the publicly visible editors' draft.

This document was published by the Accessible Rich Internet Applications Working Group as an Editor's Draft.

GitHub Issues are preferred for discussion of this specification. Alternatively, you can send comments to our mailing list. Please send them to public-aria@w3.org (archives).

Publication as an Editor's Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 1 March 2019 W3C Process Document.

1. Introduction

This section is non-normative.

The Graphics Accessibility API Mappings specification provides role mappings for the roles in the WAI-ARIA Graphics Module [GRAPHICS-ARIA-1.0].

For web documents and applications, the essential semantic information is encapsulated within the Document Object Model (DOM). Assistive technologies obtain this information from the user agent, which maps elements and attributes to the platform Accessibility API.

The original suite of element semantics defined by WAI-ARIA 1.0 only considered graphics as individual embedded images, with no interactivity or meaningful semantic structure. It was therefore not sufficient for communicating complex graphics, such as labelled diagrams or data charts, or for interactive graphics. The WAI-ARIA Graphics Module defines a core set of three roles that can convey the structure of a graphic. This specification defines how user agents should expose those roles to the accessibility APIs currently in use, so that the semantic information is available to assistive technologies that use those APIs.

For an introduction to WAI-ARIA, see the WAI-ARIA Overview. It is part of a set of resources that define and support the WAI-ARIA specification, including the following documents:

2. Conformance

The main content of this specification is normative and defines requirements that impact conformance claims. Introductory material, appendices, sections marked as "non-normative" and their subsections, diagrams, examples, and notes are informative (non-normative). Non-normative material provides advisory information to help interpret the guidelines but does not create requirements that impact a conformance claim.

Normative sections provide requirements that user agents must follow for an implementation to conform to this specification. The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, RECOMMENDED, MAY, and OPTIONAL in this document are to be interpreted as described in Keywords for use in RFCs to indicate requirement levels [RFC2119]. RFC-2119 keywords are formatted in uppercase and contained in an element with class="rfc2119". When the keywords shown above are used, but do not share this format, they do not convey formal information in the RFC 2119 sense, and are merely explanatory, i.e., informative. As much as possible, such usages are avoided in this specification.

Normative sections provide requirements that authors, user agents and assistive technologies MUST follow for an implementation to conform to this specification.

Non-normative (informative) sections provide information useful to understanding the specification. Such sections may contain examples of recommended practice, but it is not required to follow such recommendations in order to conform to this specification.

3. Important Terms

While some terms are defined in place, the following definitions are used throughout this document.

Accessibility API

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 accessibility APIs are Microsoft Active Accessibility [MSAA], Microsoft User Interface Automation [UI-AUTOMATION], MSAA with UIA Express [UIA-EXPRESS], the Mac OS X Accessibility Protocol [AXAPI], the Linux/Unix Accessibility Toolkit [ATK] and Assistive Technology Service Provider Interface [AT-SPI], and IAccessible2 [IAccessible2].

Accessibility Subtree

An accessible object in the accessibility tree and its descendants in that tree. It does not include objects which have relationships other than parent-child in that tree. For example, it does not include objects linked via aria-flowto unless those objects are also descendants in the accessibility tree.

Accessibility Tree

Tree of accessible objects that represents the structure of the user interface (UI). Each node in the accessibility tree represents an element in the UI as exposed through the accessibility API; for example, a push button, a check box, or container.

Accessible Description

An accessible description provides additional information, related to an interface element, that complements the accessible name. The accessible description might or might not be visually perceivable.

Accessible Name

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. See related accessible description.

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.

Accessible object

A node in the accessibility tree of a platform accessibility API. Accessible objects expose various states, properties, and events for use by assistive technologies. In the context of markup languages (e.g., HTML and SVG) in general, and of WAI-ARIA in particular, markup elements and their attributes are represented as accessible objects.

Activation behavior

The action taken when an event, typically initiated by users through an input device, causes an element to fulfill a defined role. The role may be defined for that element by the host language, or by author-defined variables, or both. The role for any given element may be a generic action, or may be unique to that element. For example, the activation behavior of an HTML or SVG <a> element shall be to cause the user agent to traverse the link specified in the href attribute, with the further optional parameter of specifying the browsing context for the traversal (such as the current window or tab, a named window, or a new window); the activation behavior of an HTML <input> element with the type attribute value submit shall be to send the values of the form elements to an author-defined IRI by the author-defined HTTP method.

Assistive Technologies

Hardware and/or software that:

  • relies on services provided by a user agent to retrieve and render Web content
  • works with a user agent or web content itself through the use of APIs, and
  • provides services beyond those offered by the user agent to facilitate user interaction with web content by people with disabilities

This definition may differ from that used in other documents.

Examples of assistive technologies that are important in the context of this document include the following:

  • screen magnifiers, which are used to enlarge and improve the visual readability of rendered text and images;
  • screen readers, which are most-often used to convey information through synthesized speech or a refreshable Braille display;
  • text-to-speech software, which is used to convert text into synthetic speech;
  • speech recognition software, which is used to allow spoken control and dictation;
  • alternate input technologies (including head pointers, on-screen keyboards, single switches, and sip/puff devices), which are used to simulate the keyboard;
  • alternate pointing devices, which are used to simulate mouse pointing and clicking.
Attribute

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.

Class

A set of instance objects that share similar characteristics.

Deprecated

A deprecated role, state, or property is one which has been outdated by newer constructs or changed circumstances, and which may be removed in future versions of the WAI-ARIA specification. User agents are encouraged to continue to support items identified as deprecated for backward compatibility. For more information, see Deprecated Requirements in the Conformance section.

Desktop focus event

Event from/to the host operating system via the accessibility API, notifying of a change of input focus.

Element

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.

Event

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.

Expose

Translated to platform-specific accessibility APIs as defined in the Core Accessibility API Mappings.

Graphical Document

A document containing graphic representations with user-navigable parts. Charts, maps, diagrams, blueprints, and dashboards are examples of graphical documents. A graphical document is composed using any combination of symbols, images, text, and graphic primitives (shapes such as circles, points, lines, paths, rectangles, etc).

Hidden

Indicates that the element is not visible, perceivable, or interactive to any user. An element is considered hidden if it or any one of its ancestor elements is not rendered or is explicitly hidden.

Informative

Content provided for information purposes and not required for conformance. Content required for conformance is referred to as normative.

Keyboard Accessible

Accessible to the 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 2.1 Guideline 2.1: Make all functionality available from a keyboard [WCAG21].

Landmark

A type of region on a page to which the 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 Region

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 a result of a user interaction. Examples of live regions include 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 process them: aria-live, aria-relevant, aria-atomic, and aria-busy.

Primary Content Element

An implementing host language's primary content element, such as the body element in HTML.

Managed State

Accessibility API state that is controlled by the user agent, such as focus and selection. These are contrasted with "unmanaged states" that are typically controlled by the author. Nevertheless, authors can override some managed states, such as aria-posinset and aria-setsize. Many managed states have corresponding CSS pseudo-classes, such as :focus, and pseudo-elements, such as ::selection, that are also updated by the user agent.

Nemeth Braille

The Nemeth Braille Code for Mathematics is a braille code for encoding mathematical and scientific notation. See Nemeth Braille on Wikipedia.

Node

Basic type of object in the DOM tree or accessibility tree. DOM nodes are further specified as Element or Text nodes, among other types. The nodes of an accessibility tree are accessible objects.

Normative

Required for conformance. By contrast, content identified as informative or "non-normative" is not required for conformance.

Object

In the context of user interfaces, an item in the perceptual user experience, represented in markup languages by one or more elements, and rendered by user agents.

In the context of programming, the instantiation of one or more classes and interfaces which define the general characteristics of similar objects. An object in an accessibility API may represent one or more DOM objects. Accessibility APIs have defined interfaces that are distinct from DOM interfaces.
Ontology

A description of the characteristics of classes and how they relate to each other.

Operable

Usable by users in ways they can control. References in this document relate to WCAG 2.1 Principle 2: Content must be operable [WCAG21]. See Keyboard Accessible.

Owned Element

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.

Owning Element

An 'owning element' is any DOM ancestor of the element, or any element with an aria-owns attribute which references the ID of the element.

Perceivable

Presentable to users in ways they can sense. References in this document relate to WCAG 2.1 Principle 1: Content must be perceivable [WCAG21].

Property

Attributes that are essential to the nature of a given object, or that represent a data value associated with the object. A change of a property may significantly impact the meaning or presentation of an object. Certain properties (for example, aria-multiline) are less likely to change than states, but note that the frequency of change difference is not a rule. A few properties, such as aria-activedescendant, aria-valuenow, and aria-valuetext are expected to change often. See clarification of states versus properties.

Relationship

A connection between two distinct things. Relationships may be of various types to indicate which object labels another, controls another, etc.

Role

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.

Root WAI-ARIA node

The primary element containing non-metadata content. In many languages, this is the document element but in HTML, it is the <body>.

Semantics

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.

State

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.

Sub-document

Any document created from a <frame>, <iframe> or similar mechanism. A sub-document may contain a document, an application or any widget such as a calendar pulled in from another server. In the accessibility tree there are two accessible objects for this situation—one represents the <frame>/<iframe> element in the parent document, which parents a single accessible object child representing the spawned document contents.

Target Element

An element specified in a WAI-ARIA relation. For example, in <div aria-controls=”elem1”>, where “elem1” is the ID for the target element.

Taxonomy

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.

Text node

Type of DOM node that represents the textual content of an attribute or an element. A Text node has no child nodes.

Tooltip attribute

Any host language attribute that would result in a user agent generating a tooltip such as in response to a mouse hover in desktop user agents.

Understandable

Presentable to users in ways they can construct an appropriate meaning. References in this document relate to WCAG 2.1 Principle 3: Information and the operation of user interface must be understandable [WCAG21].

User Agent

Any software that retrieves, renders and facilitates end user interaction with Web content. This definition may differ from that used in other documents.

Valid IDREF

A reference to a target element in the same document that has a matching ID

Widget

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).

4. Mapping WAI-ARIA to Accessibility APIs

4.1 General rules for exposing WAI-ARIA semantics

This section MUST conform to General rules for exposing WAI-ARIA semantics in [CORE-AAM-1.1].

5. Conflicts between native markup semantics and WAI-ARIA

User agents MUST conform to Conflicts between native markup semantics and WAI-ARIA in [CORE-AAM-1.1].

6. Exposing attributes that do not directly map to accessibility API properties

User agents MUST conform to Exposing attributes that do not directly map to accessibility API properties in [CORE-AAM-1.1].

7. Role mapping

Platform accessibility APIs traditionally have had a finite set of predefined roles that are expected by assistive technologies on that platform and only one or two roles may be exposed. In contrast, WAI-ARIA allows multiple roles to be specified as an ordered set of space-separated valid role tokens. The additional roles are fallback roles similar to the concept of specifying multiple fonts in case the first choice font type is not supported.

7.1 General Rules

User agents MUST conform to the Role Mapping General Rules accessibility API computational requirements in [CORE-AAM-1.1].

7.2 Role Mapping Table

This section defines how roles in graphics map to platform accessibility APIs based on their native host language semantics and when WAI-ARIA roles are applied. This section refers directly to the Core Accessibility API Mappings specification.

A. Change Log

The full commit history to Graphics Accessibility API Mappings 1.0 is available.

A.1 Substantive changes since the First Public Working Draft

B. Acknowledgments

This section is non-normative.

The following people contributed to the development of this document.

B.1 Participants active in the SVG accessibility task force at the time of publication

B.2 Participants active in the ARIA WG at the time of publication

B.3 Enabling funders

This publication has been funded in part with U.S. Federal funds from the Department of Education, National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR), initially under contract number ED-OSE-10-C-0067 and currently under contract number HHSP23301500054C. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

C. References

C.1 Normative references

[CORE-AAM-1.1]
Core Accessibility API Mappings 1.1. Joanmarie Diggs; Joseph Scheuhammer; Richard Schwerdtfeger; Michael Cooper; Andi Snow-Weaver; Aaron Leventhal. W3C. 14 December 2017. W3C Recommendation. URL: https://www.w3.org/TR/core-aam-1.1/
[GRAPHICS-ARIA-1.0]
WAI-ARIA Graphics Module. Amelia Bellamy-Royds; Joanmarie Diggs; Michael Cooper. W3C. 2 October 2018. W3C Recommendation. URL: https://www.w3.org/TR/graphics-aria-1.0/
[RFC2119]
Key words for use in RFCs to Indicate Requirement Levels. S. Bradner. IETF. March 1997. Best Current Practice. URL: https://tools.ietf.org/html/rfc2119

C.2 Informative references

[ACCNAME-AAM-1.1]
Accessible Name and Description Computation 1.1. Joanmarie Diggs; Bryan Garaventa; Michael Cooper. W3C. 18 December 2018. W3C Recommendation. URL: https://www.w3.org/TR/accname-1.1/
[AT-SPI]
Assistive Technology Service Provider Interface. The GNOME Project. URL: https://developer.gnome.org/libatspi/stable/
[ATK]
ATK - Accessibility Toolkit. The GNOME Project. URL: https://developer.gnome.org/atk/stable/
[AXAPI]
The NSAccessibility Protocol for macOS. Apple, Inc. URL: https://developer.apple.com/documentation/appkit/nsaccessibility
[HTML52]
HTML 5.2. Steve Faulkner; Arron Eicholz; Travis Leithead; Alex Danilo; Sangwhan Moon. W3C. 14 December 2017. W3C Recommendation. URL: https://www.w3.org/TR/html52/
[IAccessible2]
IAccessible2. Linux Foundation. URL: https://www.linuxfoundation.org/collaborate/workgroups/accessibility/iaccessible2
[MSAA]
Microsoft Active Accessibility (MSAA). Microsoft Corporation. URL: https://docs.microsoft.com/en-us/windows/win32/winauto/microsoft-active-accessibility
[SVG]
Scalable Vector Graphics (SVG) 1.0 Specification. Jon Ferraiolo. W3C. 4 September 2001. W3C Recommendation. URL: https://www.w3.org/TR/SVG/
[SVG-AAM-1.0]
SVG Accessibility API Mappings. Amelia Bellamy-Royds; Ian Pouncey. W3C. 10 May 2018. W3C Working Draft. URL: https://www.w3.org/TR/svg-aam-1.0/
[UI-AUTOMATION]
UI Automation. Microsoft Corporation. URL: https://docs.microsoft.com/en-us/windows/win32/winauto/ui-automation-specification
[UIA-EXPRESS]
The IAccessibleEx Interface. Microsoft Corporation. URL: https://docs.microsoft.com/en-us/windows/win32/winauto/iaccessibleex
[WAI-ARIA-1.0]
Accessible Rich Internet Applications (WAI-ARIA) 1.0. James Craig; Michael Cooper et al. W3C. 20 March 2014. W3C Recommendation. URL: https://www.w3.org/TR/wai-aria/
[WAI-ARIA-1.1]
Accessible Rich Internet Applications (WAI-ARIA) 1.1. Joanmarie Diggs; Shane McCarron; Michael Cooper; Richard Schwerdtfeger; James Craig. W3C. 14 December 2017. W3C Recommendation. URL: https://www.w3.org/TR/wai-aria-1.1/
[WAI-ARIA-PRACTICES-1.1]
WAI-ARIA Authoring Practices 1.1. Matthew King; JaEun Ku; James Nurthen; Zoë Bijl; Michael Cooper; Joseph Scheuhammer; Lisa Pappas; Richard Schwerdtfeger. W3C. 14 August 2019. W3C Note. URL: https://www.w3.org/TR/wai-aria-practices-1.1/
[WCAG21]
Web Content Accessibility Guidelines (WCAG) 2.1. Andrew Kirkpatrick; Joshue O Connor; Alastair Campbell; Michael Cooper. W3C. 5 June 2018. W3C Recommendation. URL: https://www.w3.org/TR/WCAG21/