Graphics Accessibility API Mappings

W3C Recommendation

This version:
https://www.w3.org/TR/2018/REC-graphics-aam-1.0-20181002/
Latest published version:
https://www.w3.org/TR/graphics-aam-1.0/
Latest editor's draft:
https://w3c.github.io/graphics-aam/
Implementation report:
https://w3c.github.io/test-results/graphics-aam/
Previous version:
https://www.w3.org/TR/2018/PR-graphics-aam-1.0-20180626/
Editors:
(Igalia, S.L.)
(W3C)
Former editors:
(IBM Corporation) (until September 2016)
(Knowbility) (until August 2017)
Authors:
(IBM Corporation)
(Knowbility)
(W3C)

Please check the errata for any errors or issues reported since publication.

See also translations.


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 the Graphics-AAM 1.0 W3C Recommendation by the Accessible Rich Internet Applications Working Group. The Working Group created a Graphics-ARIA 1.0 Implementation Report to demonstrate that the specification is implementable. A history of changes to Graphics-AAM 1.0 is available in the appendix.

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). Comments received on the Graphics-AAM 1.0 Recommendation cannot result in changes to this version of the specification, but may be addressed in errata or future versions of Graphics-ARIA. The Working Group may not make formal responses to comments but future work undertaken by the Working Group may address comments received on this document. 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 a Recommendation.

Comments regarding this document are welcome. Please send them to public-aria@w3.org (archives).

Please see the Working Group's implementation report.

This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

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 February 2018 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].

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.

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.

Informative

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

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.
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.

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.

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.

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.

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.

Table describing mapping of WAI-ARIA roles to accessibility APIs.
WAI-ARIA Role MSAA + IAccessible2 Role + Other IAccessible2 Features UIA Control Type + Other Features ATK/AT-SPI Role AXAPI
graphics-document

ROLE_SYSTEM_DOCUMENT + STATE_SYSTEM_READONLY

IAccessible2: Object attribute xml-roles:graphics-document.

Control Type: 'Document'.

Expose ROLE_DOCUMENT_FRAME and object attribute xml-roles:graphics-document.

AXRole: AXGroup
AXSubrole: AXDocument
AXRoleDescription: 'document'
graphics-object ROLE_SYSTEM_GROUPING +

IAccessible2: Object attribute xml-roles:graphics-object.

Control Type: 'Group'.

Expose ROLE_PANEL and object attribute xml-roles:graphics-object.

AXRole: AXGroup
AXSubrole: <nil>
AXRoleDescription: 'group'
graphics-symbol ROLE_SYSTEM_GRAPHIC

IAccessible2: Object attribute xml-roles:graphics-symbol.

Control Type: 'Image'.

Expose ROLE_IMAGE and object attribute xml-roles:graphics-symbol.

AXRole: AXImage
AXSubrole: <nil>
AXRoleDescription: 'image'

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. 26 June 2018. W3C Proposed 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 and API Mappings 1.1. Joseph Scheuhammer; James Craig; Andi Snow-Weaver; Aaron Leventhal. W3C. 17 March 2016. W3C Working Draft. URL: https://www.w3.org/TR/accname-aam-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) 2.0. Microsoft Corporation. URL: https://msdn.microsoft.com/en-us/library/ms697707.aspx
[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://msdn.microsoft.com/en-us/library/ee684009%28v=vs.85%29.aspx
[UIA-EXPRESS]
The IAccessibleEx Interface. Microsoft Corporation. URL: https://msdn.microsoft.com/en-us/library/windows/desktop/dd561898%28v=vs.85%29.aspx
[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; James Nurthen; Zoë Bijl; Michael Cooper; Joseph Scheuhammer; Lisa Pappas; Richard Schwerdtfeger. W3C. 26 July 2018. 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/