[contents]  

W3C

Techniques for User Agent Accessibility Guidelines 1.0

W3C Working Draft 23 October 2000

This version:
http://www.w3.org/TR/2000/WD-UAAG10-TECHS-20001023
(plain text, gzip PostScript, gzip PDF, gzip tar file of HTML, zip archive of HTML)
Latest version:
http://www.w3.org/TR/UAAG10-TECHS
Previous version:
http://www.w3.org/TR/2000/WD-UAAG10-TECHS-20000310
Editors:
Ian Jacobs, W3C
Jon Gunderson, University of Illinois at Urbana-Champaign
Eric Hansen, Educational Testing Service
Authors and Contributors:
Refer to acknowledgements.

Copyright ©1999 - 2000 W3C® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply.

Abstract

This document provides techniques for satisfying the checkpoints defined in "Techniques for User Agent Accessibility Guidelines 1.0" [UAAG10]. These techniques cover the accessibility of user interfaces, content rendering, application programming interfaces (APIs), and languages such as the Hypertext Markup Language (HTML), Cascading Style Sheets (CSS) and the Synchronized Multimedia Integration Language (SMIL).

Status of this document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.

This is the 23 October 2000 Working Draft of Techniques for User Agent Accessibility Guidelines 1.0, for review by W3C Members and other interested parties. It is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". This is work in progress and does not imply endorsement by, or the consensus of, either W3C or participants in the WAI User Agent (UA) Working Group.

While Techniques for User Agent Accessibility Guidelines 1.0 strives to be a stable document (as a W3C Recommendation), the current document is expected to evolve as technologies change and content developers discover more effective techniques for designing accessible Web sites and pages.

Please send comments about this document, including suggestions for additional techniques, to the public mailing list w3c-wai-ua@w3.org; public archives are available.

This document is part of a series of accessibility documents published by the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C). WAI Accessibility Guidelines are produced as part of the WAI Technical Activity. The goals of the User Agent Accessibility Guidelines Working Group are described in the charter.

A list of current W3C Recommendations and other technical documents can be found at the W3C Web site.

Table of contents

Note: With a user agent that implements HTML 4 [HTML4] access keys, readers may navigate directly to the table of contents via the "c" character. Users may have to use additional keyboard strokes depending on their operating environment.

Related resources

"Techniques for User Agent Accessibility Guidelines 1.0" and the "User Agent Accessibility Guidelines 1.0" [UAAG10] are part of a series of accessibility guidelines published by the Web Accessibility Initiative (WAI). These documents explain the responsibilities of user agent developers in making the Web accessibility to users with disabilities. The series also includes the "Web Content Accessibility Guidelines 1.0" [WCAG10] (and techniques [WCAG10-TECHS] and evaluation and repair techniques [AERT]), which explain the responsibilities of authors, and the "Authoring Tool Accessibility Guidelines 1.0" [ATAG10] (and techniques [ATAG10-TECHS]), which explain the responsibilities of authoring tool developers.

1 Introduction

This document suggests some techniques for satisfying the requirements of the "Techniques for User Agent Accessibility Guidelines 1.0" [UAAG10]. The techniques listed in this document are not required for conformance to the Guidelines. These techniques are not necessarily the only way of satisfying the checkpoint, nor are they a definitive set of requirements for satisfying a checkpoint.

2 The user agent accessibility guidelines

This section lists each checkpoint of "Techniques for User Agent Accessibility Guidelines 1.0" [UAAG10] along with some possible techniques for satisfying it. Each checkpoint definition includes a link to the checkpoint definition in "Techniques for User Agent Accessibility Guidelines 1.0". Each checkpoint definition is followed by a list of techniques, information about related resources, and references to the accessibility topics in section 3. The accessibility topics of section 3 apply to more than one checkpoint.

Note: Most of the techniques in this document are designed for mainstream (graphical) browsers and multimedia players. However, some of them also make sense for assistive technologies and other user agents. In particular, techniques about communication between user agents will benefit assistive technologies. Refer, for example, to the appendix on loading assistive technologies for access to the document object model.

Priorities

Each checkpoint in this document is assigned a priority that indicates its importance for users with disabilities.

[Priority 1]
This checkpoint must be satisfied by user agents, otherwise one or more groups of users with disabilities will find it impossible to access the Web. Satisfying this checkpoint is a basic requirement for enabling some people to access the Web.
[Priority 2]
This checkpoint should be satisfied by user agents, otherwise one or more groups of users with disabilities will find it difficult to access the Web. Satisfying this checkpoint will remove significant barriers to Web access for some people.
[Priority 3]
This checkpoint may be satisfied by user agents to make it easier for one or more groups of users with disabilities to access information. Satisfying this checkpoint will improve access to the Web for some people.

Note: This information about checkpoint priorities is included for convenience only. For detailed information about conformance to "Techniques for User Agent Accessibility Guidelines 1.0" [UAAG10], please refer to that document.

Guideline 1. Support input and output device-independence.

Checkpoints for communication with other software:

1.1 Ensure that every functionality available through the user interface is also available through every input API that is implemented by the user agent. This checkpoint does not require developers to reimplement the input methods associated with the keyboard, pointing device, voice, and other input APIs. [Priority 1] (Checkpoint 1.1)
Note: This checkpoint does not require developers to implement all operating system input APIs, only to make the software accessible through those they do implement. Developers are not required to reimplement input methods of APIs, e.g., text input through a mouse API or pointer motion through a keyboard API.

Techniques:

Ensure that the user can do the following with all supported input devices:

Ensure that people with disabilities are involved in the design and testing of the software.

1.2 Use the standard input and output APIs of the operating system. Do not bypass the standard output APIs when rendering information. [Priority 1] (Checkpoint 1.2)
Note: For example, do not bypass (for reasons of speed, efficiency, etc.) standard APIs to manipulate the memory associated with rendered content, since assistive technologies may monitor rendering through the APIs. When available, developers should use APIs at a higher level of abstraction than the standard device APIs for the operating system. If these higher level APIs do not use the standard device APIs properly, developers should also use the standard device APIs.

Techniques:

1.3 Implement the operating system's standard API for the keyboard and ensure that every functionality available through the user interface is available through this API. [Priority 1] (Checkpoint 1.3)
Note: This checkpoint is an important special case of checkpoint 1.1. Refer also to checkpoint 9.8.

Techniques:

Checkpoints for user interface accessibility:

1.4 Ensure that the user can interact with all active elements in a device-independent manner. [Priority 1] (Checkpoint 1.4)
Note: For example, users without a pointing device (such as some users who are blind or have physical disabilities) must be able to activate form controls and links (including the links in a client-side image map). This checkpoint is an important special case of checkpoint 1.1.

Techniques:

1.5 Ensure that every message (e.g., prompt, alert, notification, etc.) that is a non-text element and is part of the user agent user interface has a text equivalent. [Priority 1] (Checkpoint 1.5)
Note: For example, if the user is alerted of an event by an audio cue, a visually-rendered text equivalent in the status bar would satisfy this checkpoint. Per checkpoint 5.4, a text equivalent for each such message must be available through a standard API. Refer also to checkpoint 5.5.

Techniques:

Guideline 2. Ensure user access to all content.

Checkpoints for content accessibility:

2.1 Make all content available through the user interface. [Priority 1] (Checkpoint 2.1)
Note: Users must have access to the entire document object through the user interface, including recognized equivalents, attributes, style sheets, etc. This checkpoint does not require that all content be available in every viewport. A document source view is an important part of a solution for providing access to content, but is not a sufficient solution on its own for all content. Refer to guideline 5 for more information about programmatic access to content.

Techniques:

2.2 For a presentation that requires user input within a specified time interval, allow the user to configure the user agent to pause the presentation automatically and await user input before proceeding. [Priority 1] (Checkpoint 2.2)
Note: In this configuration, the user agent may have to pause the presentation more than once, depending on the number of times input is requested.

Techniques:

2.3 Provide easy access to each equivalent and each equivalency target through at least one of the following mechanisms: (1) allowing configuration to render the equivalent instead of the equivalency target; (2) allowing configuration to render the equivalent in addition to the equivalency target; (3) allowing the user to select the equivalency target and then inspect its equivalents; (4) providing a direct link to the equivalent in content, just before or after the equivalency target in document order. [Priority 1] (Checkpoint 2.3)
Note: For example, if an image in an HTML document has text equivalents, provide access to them (1) by replacing the image with the rendered equivalents, (2) by rendering the equivalents near the image, (3) by allowing the user to select the image and then inspect its equivalents, or (4) by allowing the user to follow readily available links to the equivalents.

Techniques:

How the user selects preferred natural language for captions in Real Player

This image shows how users select a natural language preference in the Real Player. This setting, in conjunction with language markup in the presentation, determines what content is rendered.

2.4 Allow the user to specify that text transcripts, collated text transcripts, captions, and auditory descriptions be rendered at the same time as the associated audio and visual tracks. Respect author-specified synchronization cues during rendering. [Priority 1] (Checkpoint 2.4)

Techniques:

2.5 For non-text content that has no recognized text equivalent, allow configuration to generate repair text. If the non-text content is included by URI reference, base the repair text on the URI reference and content type of the Web resource. Otherwise, base the repair text on the name of the element that includes the non-text content. [Priority 2] (Checkpoint 2.5)
Note: For information on URI references, refer to "Uniform Resource Identifiers (URI): Generic Syntax" ([RFC2396], section 4). Some markup languages (such as HTML 4 [HTML4] and SMIL 1.0 [SMIL] require the author to provide text equivalents for some content. When they don't, the user agent is required by this document to generate repair text. Refer also to checkpoint 2.6.

Techniques:

2.6 Allow configuration so that when the author has specified an empty text equivalent for non-text content, the user agent generates no repair text or generates repair text as required by checkpoint 2.5. [Priority 3] (Checkpoint 2.6)
Note: An empty text equivalent (e.g., alt="") is considered to be a valid text equivalent in some authoring scenarios. For instance, when some non-text content has no other function than pure decoration, or an image is part of a "mosaic" of several images and doesn't make sense out of the mosaic. Please refer to the Web Content Accessibility Guidelines 1.0 [WCAG10] for more information about text equivalents. Refer also to checkpoint 2.5.

Techniques:

2.7 Allow the user to configure the user agent not to render content marked up in a recognized but unsupported natural language. Indicate to the user in context that author-supplied content has not been rendered. [Priority 3] (Checkpoint 2.7)
Note: For example, use a text substitute or a graphical icon to indicate that content in a particular language has not been rendered. If a graphical icon is used, make the text substitute its text equivalent.

Techniques:

Guideline 3. Allow the user to configure the user agent not to render some content that may reduce accessibility.

In addition to the techniques below, refer also to the section on user control of style.

Checkpoints for content accessibility:

3.1 Allow the user to configure the user agent not to render background images. In this configuration, provide an option to alert the user when a background image is available but has not been rendered. [Priority 1] (Checkpoint 3.1)
Note: This checkpoint only requires control of background images for "two-layered renderings", i.e., one rendered background image with all other content rendered "above it". When background images are not rendered, user agents should render a solid background color (refer to checkpoint 4.4 and checkpoint 4.3). In this configuration, the user agent is not required to retrieve background images from the Web.

Techniques:

3.2 Allow the user to configure the user agent not to render audio, video, or animated images except on explicit request from the user. In this configuration, provide an option to render a substitute placeholder in context for each unrendered source of audio, video, or animated image. When placeholders are rendered, allow the user to activate each placeholder individually and replace it with the original author-supplied content. [Priority 1] (Checkpoint 3.2)
Note: This checkpoint requires configuration for content rendered without any user interaction (including content rendered on load or as the result of a script) as well as content rendered as the result of user interaction that is not an explicit request (e.g., when the user activates a link). Activation of a placeholder is considered an explicit user request to render the original content. When configured not to render content except on explicit user request, user agents may render the content "invisibly" or "silently" (i.e., in a manner that doesn't appear through the viewport). In this configuration, the user agent is not required to retrieve the audio, video, or animated image from the Web until requested by the user. Refer also checkpoint 4.6, checkpoint 4.10 and checkpoint 4.11.

Techniques:

3.3 Allow the user to configure the user agent to render animated or blinking text as motionless text. [Priority 1] (Checkpoint 3.3)

Techniques:

3.4 Allow the user to configure the user agent to render blinking images as motionless images. [Priority 1] (Checkpoint 3.4)

Techniques:

3.5 Allow the user to configure the user agent not to execute scripts or applets. In this configuration, provide an option to alert the user when scripts or applets are available. [Priority 1] (Checkpoint 3.5)

Techniques:

3.6 Allow configuration so that an author-specified "client-side redirect" (i.e., one initiated by the user agent, not the server) does not change content except on explicit user request. Allow the user to access the new content manually (e.g., by following a link). [Priority 2] (Checkpoint 3.6)

Techniques:

3.7 Allow configuration so that author-specified content refreshes do not change content except on explicit user request. Allow the user to request the new content manually (e.g., by activating a button or following a link). Continue to alert the user, according to schedule specified by the author, that a manual request will refresh the content. [Priority 2] (Checkpoint 3.7)

Techniques:

3.8 Allow the user to configure the user agent not to render images. [Priority 2] (Checkpoint 3.8)

Techniques:

Guideline 4. Ensure user control of styles.

In addition to the techniques below, refer also to the section on user control of style.

Checkpoints for fonts and colors (content accessibility):

4.1 Allow the user to configure and control the reference size of rendered text with an option to override author-specified and user agent default sizes of rendered text. Make available the range of system font sizes. [Priority 1] (Checkpoint 4.1)
Note: The reference size of rendered text corresponds to the default value of the CSS2 'font-size' property, which is 'medium' (refer to CSS2 [CSS2], section 15.2.4). The default reference size of rendered text may vary among user agents. User agents may offer different mechanisms to allow the user to control the size of rendered text, for example by allowing the user to change the font size or by allowing the user to zoom or magnify content (refer, for example to the Scalable Vector Graphics specification [SVG]).

Techniques:

4.2 Allow the user to configure the font family of all text, with an option to override author-specified, and user agent default, font families. Allow the user to select from among the range of system font families. [Priority 1] (Checkpoint 4.2)
Note: For example, allow the user to specify that all text must be rendered in a particular sans-serif font family.

Techniques:

4.3 Allow the user to configure the foreground color of all text, with an option to override author-specified, and user agent default, foreground colors. Allow the user to select from among the range of system colors. [Priority 1] (Checkpoint 4.3)

Techniques:

4.4 Allow the user to configure the background color of all text, with an option to override author-specified and user agent default background colors. Allow the user to select from among the range of system colors. [Priority 1] (Checkpoint 4.4)

Techniques:

Checkpoints for multimedia presentations, audio-only presentations, and visual-only presentations (content accessibility):

4.5 Allow the user to slow the presentation rate of audio, video and animations that are not recognized as style. For a visual track, provide at least one setting between 40% and 60% of the original speed. For a prerecorded audio track including audio-only presentations, provide at least one setting between 75% - 80% of the original speed. When the user agent allows the user to slow the visual track of a synchronized multimedia presentation to between 100% and 80% of its original speed, synchronize the visual and audio tracks. Below 80%, the user agent is not required to render the audio track. [Priority 1] (Checkpoint 4.5)
Refer also to checkpoint 2.4.

Techniques:

4.6 Allow the user to stop, pause, resume, fast advance, and fast reverse audio, video, and animations that last three or more seconds at their default playback rate and that are not recognized as style. [Priority 1] (Checkpoint 4.6)
Note: This checkpoint applies to content that is rendered automatically or on request from the user. Enable control of each independent source recognized as distinct. Respect synchronization cues per checkpoint 2.4. Refer also to checkpoint 3.2.

Techniques:

4.7 For graphical viewports, allow the user to position text transcripts, collated text transcripts, and captions in the viewport. Allow the user to choose from among the same range of positions available to the author (e.g., the range of positions allowed by the markup or style language). [Priority 1] (Checkpoint 4.7)

Techniques:

4.8 Allow the user to slow the presentation rate of audio, video and animations not covered by checkpoint 4.5. The same speed percentage requirements of checkpoint 4.5 apply. [Priority 2] (Checkpoint 4.8)
Note: User agents automatically satisfy this checkpoint if they satisfy checkpoint 4.5 for every audio, video, and animation.

Techniques:

Refer to the techniques of checkpoint 4.5.
4.9 Allow the user to stop, pause, resume, fast advance, and fast reverse audio, video, and animations not covered by checkpoint 4.6. [Priority 2] (Checkpoint 4.9)
Note: User agents automatically satisfy this checkpoint if they satisfy checkpoint 4.6 for every audio, video, and animation.

Techniques:

Refer to the techniques of checkpoint 4.6.

Checkpoints for audio volume control (content accessibility):

4.10 Allow the user to configure and control the global audio volume. The user must be able to choose zero volume (i.e., silent). [Priority 1] (Checkpoint 4.10)
Note: User agents should allow global control of volume through available system-level controls.

Techniques:

4.11 Allow the user to control independently the volumes of distinct audio sources synchronized to play simultaneously. [Priority 1] (Checkpoint 4.11)
Note: Refer also to checkpoint 4.13.

Techniques:

Checkpoints for synthesized speech (content accessibility):

Refer also to techniques for synthesized speech.

4.12 Allow the user to configure and control synthesized speech playback rate according to the full range offered by the speech synthesizer. The lower bound for this range must be at most 120 words per minute. The upper bound for this range must be at least 400 words per minute. The user must be able to increase or decrease the playback rate in increments of 5% of the current playback rate. [Priority 1] (Checkpoint 4.12)

Techniques:

4.13 Allow the user to control the synthesized speech volume independently of other sources of audio. [Priority 1] (Checkpoint 4.13)
Note: Refer also to checkpoint 4.11.

Techniques:

4.14 Allow the user to configure synthesized voice gender, pitch, pitch range, stress, richness, and control of spelling, punctuation, and number processing according to the full range of values offered by the speech synthesizer. [Priority 2] (Checkpoint 4.14)
Note: This list of voice characteristic properties is based on the list in section 19.8 of Cascading Style Sheets Level 2 [CSS2]. Ranges of values for these properties may vary among speech synthesizers.

Techniques:

Checkpoints for user interface accessibility:

4.15 For user agents that support style sheets, allow the user to select from (and apply) available author and user style sheets or to ignore them. [Priority 1] (Checkpoint 4.15)
Note: By definition, the user agent's default style sheet is always present, but may be overridden by author or user styles.

Techniques:

4.16 Allow the user to configure how the selection is highlighted (e.g., foreground and background color, voice pitch, etc.). For graphical viewports, offer at least three rendering options, including colors and fonts. Allow the user to select from among the range of system colors and fonts. [Priority 1] (Checkpoint 4.16)
Note: For information for control of speech output and using those parameters for highlighting, refer to checkpoint 4.14.

Techniques:

4.17 Allow the user to configure how the content focus is highlighted (e.g., foreground and background color, voice pitch, etc.). For graphical viewports, offer at least three rendering options, including colors and fonts. For graphical viewports, allow the user to select from among the range of system colors and fonts. The default focus highlight mechanism must be different from the default selection highlight mechanism. [Priority 1] (Checkpoint 4.17)
Note: For information for control of speech output and using those parameters for highlighting, refer to checkpoint 4.14.

Techniques:

4.18 Allow the user to configure whether the current focus moves automatically to a viewport that opens without an explicit request from the user. [Priority 2] (Checkpoint 4.18)

Techniques:

4.19 Ensure that when a viewport's selection or content focus changes, it is in the viewport after the change. [Priority 2] (Checkpoint 4.19)
Note: For example, if users navigating links move to a portion of the document outside a graphical viewport, the viewport should scroll to include the new location of the focus. Or, for users of audio viewports, allow configuration to render the selection or focus immediately after the change.

Techniques:

4.20 Allow the user to configure the user agent to only open viewports on explicit user request. In this configuration, instead of opening a viewport automatically, alert the user and allow the user to open it manually. Allow the user to close viewports. [Priority 2] (Checkpoint 4.20)
Note: User creation of a new viewport (e.g., empty or with a new resource loaded) through the user agent's user interface constitutes an explicit user request. Refer also to checkpoint 4.18 and checkpoint 5.5.

Techniques:

4.21 For graphical user interfaces, allow the user to configure the user agent so that the viewport with the current focus remains "on top" of all other viewports. In this configuration, when a viewport opens without explicit user request, alert the user. [Priority 2] (Checkpoint 4.21)

Techniques:

Guideline 5. Observe system conventions and standard interfaces.

Checkpoints for communication with other software:

5.1 Provide programmatic read access to HTML and XML content by conforming to the W3C Document Object Model (DOM) Level 2 Core and HTML Specifications and exporting the interfaces they define. [Priority 1] (Checkpoint 5.1)
Note: These specifications are defined the "Document Object Model (DOM) Level 2 Core Specification" [DOM2CORE] and the "Document Object Model (DOM) Level 2 HTML Specification" [DOM2HTML]. Please refer to those specifications for information about which versions of HTML and XML the specifications cover and for the definition of a "read-only" DOM. For content other than HTML and XML, refer to checkpoint 5.3.

Techniques:

5.2 If the user can modify HTML and XML content through the user interface, provide the same functionality programmatically by conforming to the W3C Document Object Model (DOM) Level 2 Core and HTML Specifications and exporting the interfaces they define. [Priority 1] (Checkpoint 5.2)
Note: For example, if the user interface allows users to complete HTML forms, this must also be possible through the DOM APIs. These specifications are defined the "Document Object Model (DOM) Level 2 Core Specification" [DOM2CORE] and the "Document Object Model (DOM) Level 2 HTML Specification" [DOM2HTML]. Please refer to those documents for information about which versions of HTML and XML the specifications cover. For markup languages other than HTML and XML, refer to checkpoint 5.3.

Techniques:

Allowing assistive technologies write access through the DOM allows them to:

The ability to write to the DOM can improve performance for the assistive technology. For example, if an assistive technology has already traversed a portion of the document object and knows that a section (e.g., a style element) could not be rendered, it can mark this section "to be skipped".

Another benefit is to add information necessary for audio rendering but that would not be stored directly in the DOM during parsing. Consider an ordered list. The Internet Explorer 5.5 [IE-WIN] document object model for HTML tells you that list elements are part of an ordered list but does not tell you each list element's number. The assistive technology can add the list element number to each list entry in its attribute list, for audio rendering. Furthermore, the assistive technology component that added the numeric information can mark that section as having been traversed and updated to prevent having to recompute and store the numeric information on the next pass through by the user.

Refer also to techniques for checkpoint 5.1.

5.3 For markup languages other than HTML and XML, provide programmatic access to content using standard APIs (e.g., platform-independent APIs and standard APIs for the operating system). [Priority 1] (Checkpoint 5.3)
Note: This checkpoint addresses content not covered by checkpoints checkpoint 5.1 and checkpoint 5.2.

Techniques:

5.4 Provide programmatic read and write access to user agent user interface controls using standard APIs (e.g., platform-independent APIs such as the W3C DOM; standard APIs defined for a specific operating system; and conventions for programming languages, plug-ins, virtual machine environments, etc.) [Priority 1] (Checkpoint 5.4)
Note: For example, provide access to information about the user agent's current input configuration so that assistive technologies can trigger functionalities through keyboard events, mouse events, etc.

Techniques:

5.5 Using standard APIs, provide programmatic alert of changes to content and user interface controls (including selection, content focus, and user interface focus). [Priority 1] (Checkpoint 5.5)
Note: Use the standard APIs required by guideline 5.

Techniques:

5.6 Ensure that programmatic exchanges proceed in a timely manner. [Priority 2] (Checkpoint 5.6)
Note: For example, the programmatic exchange of information required by other checkpoints in this document must be efficient enough to prevent information loss, a risk when changes to content or user interface occur more quickly than the communication of those changes. The techniques for this checkpoint explain how developers can reduce communication delays, e.g., to ensure that assistive technologies have timely access to the document object model and other information needed for accessibility.

Techniques:

5.7 For user agents that implement Cascading Style Sheets (CSS), provide programmatic access to CSS style sheets by conforming to the W3C Document Object Model (DOM) Level 2 Style Specification and exporting the interfaces it defines. [Priority 3] (Checkpoint 5.7)
Note: As of the publication of this document, Cascading Style Sheets (CSS) are defined by CSS Level 1 [CSS1] and CSS Level 2 [CSS2]. The DOM style specification is defined by "Document Object Model (DOM) Level 2 Style Specification" [DOM2STYLE]. Please refer to that specification for information about which versions of CSS the DOM style specification covers.

Techniques:

Checkpoints for user interface accessibility:

5.8 Follow operating system conventions that benefit accessibility. In particular, follow conventions for user interface design, keyboard configuration, product installation, and documentation. [Priority 2] (Checkpoint 5.8)
Note: Operating system conventions that benefit accessibility are those described in this document and in platform-specific accessibility guidelines. Some of these conventions (e.g., sticky keys, mouse keys, show sounds, etc.) are discussed in the Techniques document [UAAG10-TECHS]. Refer also to checkpoint 9.2.

Techniques:

Guideline 6. Implement specifications that promote accessibility.

Checkpoints for content accessibility:

6.1 Implement the accessibility features of all implemented specifications (markup languages, style sheet languages, metadata languages, graphics formats, etc.). The accessibility features of a specification are those identified as such and those that satisfy all of the requirements of the "Web Content Accessibility Guidelines 1.0" [WCAG10]. [Priority 1] (Checkpoint 6.1)

Techniques:

6.2 Use and conform to W3C Recommendations when they are available and appropriate for a task. [Priority 2] (Checkpoint 6.2)
Note: For instance, for markup, conform to HTML 4 [HTML4], XHTML 1.0 [XHTML10], or XML 1.0 [XML]. For style sheets, conform to CSS ([CSS1], [CSS2]). For mathematics, conform to MathML [MATHML]. For synchronized multimedia, implement SMIL 1.0 [SMIL]. For information about programmatic access to HTML and XML content, refer to guideline 5. User agents may conform to other specifications in addition to those required by this checkpoint. For reasons of backward compatibility, user agents should continue to implement deprecated features of specifications. Information about deprecated language features is generally part of the language's specification.

Techniques:

Guideline 7. Provide navigation mechanisms.

Checkpoints for user interface accessibility:

7.1 Allow the user to navigate among all viewports (including frames). [Priority 1] (Checkpoint 7.1)
Note: For example, when all frames of a frameset are displayed side-by-side, allow the user to navigate among them with the keyboard. Or, when frames are accessed or viewed one at a time (e.g., by a text browser or speech synthesizer), provide a list of links to other frames. Navigation among all viewports implies at least allowing the user to cycle through all viewports. Navigating into a viewport makes it the current viewport.

Techniques:

7.2 Associate a point of regard with each state in a viewport's browsing history and when the user returns to a state in the history, restore the associated point of regard. [Priority 1] (Checkpoint 7.2)
Note: For example, when the user navigates from one viewport to another (per checkpoint 7.1) and back, restore the point of regard.

Techniques:

7.3 Allow the user to navigate all active elements. If the author has not specified a navigation order, allow at least forward sequential navigation of elements, in document order. [Priority 1] (Checkpoint 7.3)
Note: Navigation may include non-active elements in addition to active elements. This checkpoint is an important special case of checkpoint 7.6.

Techniques:

Sequential navigation techniques

JAWS for Windows Links List view

This image shows how JAWS for Windows [JFW] allows users to navigate to links in a document and activate them independently. Users may also configure the user agent to navigate visited links, unvisited links, or both. Users may also change the sequential navigation order, sorting links alphabetically or leaving them in the logical tabbing order. The focus in the links view follows the focus in the main view.

Direct navigation techniques

7.4 Allow the user to choose to navigate only active elements. If the author has not specified a navigation order, allow at least forward and reverse sequential navigation of active elements, in document order. [Priority 2] (Checkpoint 7.4)

Techniques:

7.5 Allow the user to search forward through text content that has been rendered. The search must encompass all text within the viewport, both inside and outside the point of regard. Allow the user to start a search from any selected or focused location in content. When there is a match, allow the user to search for the next instance of the text from the location of the match. When there is a match, move the point of regard so that the matched text is in the viewport. Alert the user when there is no match. Provide a case-insensitive search option when applicable to the natural language of text. [Priority 2] (Checkpoint 7.5)
Note: The default search starting point should be the beginning of content. Use operating system conventions for indicating the result of a search (e.g., selection or content focus).

Techniques:

7.6 Allow the user to navigate efficiently to and among important structural elements identified by the author. Allow forward and backward sequential navigation to important structural elements. [Priority 2] (Checkpoint 7.6)
Note: This specification intentionally does not identify the set of "important elements" that must be navigable; refer to the Techniques document [UAAG10-TECHS] for information about identifying important elements. Structured navigation of headings, tables, forms, lists, etc., is most effective in conjunction with a configurable view (refer to configuration requirements of checkpoint 8.4 and checkpoint 7.7). User agents should follow operating system conventions for indicating navigation progress (e.g., selection or content focus).

Techniques:

User agents should construct the navigation view with the goal of breaking content into sensible pieces according to the author's design. In most cases, user agents should not break down content into individual elements for navigation; element-by-element navigation of the document object does not meet the goal of facilitating navigation to important pieces of content.

Instead, user agents are expected to construct the navigation view from author-supplied markup. For those languages with known conventions for identifying important components, user agents should construct the navigation tree from those components, allowing users to navigate up and down the document tree, and forward and backward among siblings. As the same time, allow users to shrink and expand portions of the document tree. For instance, if a subtree consists of a long series of links, this will pose problems for users with serial access to content. At any level in the document tree (for forward and backward navigation of siblings), limit the number of siblings to between five and ten. Break longer lists down into structured pieces so that users can access content efficiently, decide whether they want to explore it in detail, or skip it an move on.

Tables and forms illustrate the utility of a recursive navigation mechanism. The user should be able to navigate to tables, then change "scope" and navigate within the cells of that table. Nested tables (a table within the cell of another table) fit nicely within this scheme. However, the headers of an nested table may provide important context for the cells of the same row(s) or column(s) containing the nested table. The same ideas apply to forms: users should be able to navigate to a form, then among the controls within that form.

User agents should allow users to:

  1. Navigate to a piece of content that the author has identified as important according to the markup language specification and conventional usage. In HTML, for example, this includes headings, forms, tables, navigation mechanisms, and lists.
  2. Navigate past that piece of content (i.e., avoid the details of that component).
  3. Navigate into that piece of content (i.e., chose to view the details of that component).
  4. Change the navigation view as they go, expanding and contracting portions of content that they wish to examine or ignore. This will speed up navigation and promote orientation at the same time.
7.7 Allow the user to configure and control the set of important elements required by checkpoint 7.6 and checkpoint 8.4. Allow the user to include and exclude element types in the set of elements. [Priority 3] (Checkpoint 7.7)
Note: For example, allow the user to navigate only paragraphs, or only headings and paragraphs, etc. Refer also to checkpoint 5.4.

Techniques:

Guideline 8. Orient the user.

Checkpoints for content accessibility:

8.1 Make available to the user the author-specified purpose of each table and the author-specified relationships among the table cells and headers. [Priority 1] (Checkpoint 8.1)
Note: Depending on the table, some techniques may be more efficient than others for conveying data relationships. For many tables, user agents rendering in two dimensions may satisfy this checkpoint by rendering a table as a grid and by ensuring that users can find headers associated with cells. However, for large tables or small viewports, allowing the user to query cells for information about related headers may improve access. Refer also to checkpoint 5.3. This checkpoint is an important special case of checkpoint 2.1.

Techniques:

Internet Explorer context menu item to display table cell header information

This image shows how Internet Explorer [IE-WIN] provides cell header information through the context menu.

8.2 Render recently visited links in a distinct style and allow the user to configure this style. For graphical viewports, offer at least three rendering options, including colors and fonts. Allow the user to select from among the range of system colors and fonts. [Priority 2] (Checkpoint 8.2)
Note: Do not use color as the only distinguishing factor between visited and unvisited links as some users may not perceive colors and some devices may not render them. This checkpoint is an important special case of checkpoint 8.5.

Techniques:

The Opera dialog box for configuring the rendering of links

This image shows how Opera [OPERA] allows the user to configure link rendering, including the identification of visited links.

8.3 Render in a distinct style those links that have been marked up to indicate that following them will involve a fee and allow the user to configure this style. For graphical viewports, offer at least three rendering options, including colors and fonts. Allow the user to select from among the range of system colors and fonts. [Priority 2] (Checkpoint 8.3)
Note: This checkpoint is an important special case of checkpoint 8.5.

Techniques:

8.4 Make available to the user an "outline" view of content, composed of labels for important structural elements (e.g., heading text, table titles, form titles, etc.). For discussion about what constitutes the set of important structural elements, please refer to checkpoint 7.6. [Priority 2] (Checkpoint 8.4)
Note: This checkpoint is meant to allow the user to simplify the view of content by hiding some content selectively. For example, for each frame in a frameset, provide a table of contents composed of headings (e.g., the H1 - H6 elements in HTML) where each entry in the table of contents links to the heading in the document. This checkpoint does not require that the outline view be navigable, but this is recommended; refer to checkpoint 7.6. For those elements that do not have associated text titles or labels, the user agent should generate a brief text label (e.g., from content, the element type, etc.). Refer also to checkpoint 7.7.

Techniques:

Amaya table of contents view

This image shows the table of contents view provided by Amaya [AMAYA]. This view is coordinated with the main view so that users may navigate in one viewport and the focus follows in the other. An entry in the table of contents with a target icon means that the heading in the document has an associated anchor.

8.5 To help the user decide whether to traverse a link, make available the following information about it: link content, link title, whether the link is internal to the local resource, whether the user has traversed the link recently, whether traversing it may involve a fee, and information about the type, size, and natural language of linked Web resources. The user agent is not required to compute or make available information that requires retrieval of linked Web resources. [Priority 3] (Checkpoint 8.5)

Techniques:

Checkpoints for user interface accessibility:

8.6 Implement selection, content focus, and user interface focus mechanisms. Implement them according to system conventions (per checkpoint 5.8). [Priority 1] (Checkpoint 8.6)
Note: This checkpoints refers to the logical selection and focus; rendering requirements are addressed by checkpoint 8.7, checkpoint 4.17, and checkpoint 4.16. Refer also to checkpoint 7.1.

Techniques:

8.7 Provide a mechanism for highlighting the current viewport, selection, and content focus. [Priority 1] (Checkpoint 8.7)
Note: This includes highlighting and identifying frames. This checkpoint is an important special case of checkpoint 1.1. Refer also to checkpoints checkpoint 4.16, checkpoint 5.8, and checkpoint 8.5.

Techniques:

Example of a solid line border used to indicate the content focus in Opera 3.60

This image shows how Opera [OPERA] uses a solid line border to indicate content focus.

Example of system highlight colors used to indicate the content focus by the accessible browser project

This image shows how the Accessible Web Browser [AWB] uses the system highlight colors to indicate content focus.

8.8 Provide a mechanism for highlighting and identifying active elements. [Priority 2] (Checkpoint 8.8)
Note: On most systems, the focus is used to identify and highlight active elements.

Techniques:

8.9 Allow configuration so the user is prompted to confirm any form submission not caused by explicit user request to activate a form submit control. [Priority 2] (Checkpoint 8.9)
Note: For example, do not submit a form automatically when a menu option is selected, when all fields of a form have been filled out, or when a mouseover event occurs. The user agent may satisfy this checkpoint by prompting the user to confirm all form submissions.

Techniques:

8.10 Indicate the relative position of the viewport in rendered content (e.g., the proportion of an audio or video clip that has been played, the proportion of a Web page that has been viewed, etc.). [Priority 3] (Checkpoint 8.10)
Note: The user agent may calculate the relative position according to content focus position, selection position, or viewport position, depending on how the user has been browsing. The user agent may indicate the proportion of content viewed in a number of ways, including as a percentage, as a relative size in bytes, etc. For two-dimensional renderings, relative position includes both vertical and horizontal positions.

Techniques:

Guideline 9. Allow configuration and customization.

Checkpoints for user interface accessibility:

9.1 Provide information to the user about current user preferences for input configurations (e.g., keyboard or voice bindings). [Priority 1] (Checkpoint 9.1)

Techniques:

9.2 Avoid default input configurations that interfere with operating system accessibility conventions. [Priority 1] (Checkpoint 9.2)
Note: In particular, default configurations should not interfere with operating conventions for keyboard accessibility. Information about operating system accessibility conventions is available in the Techniques document [UAAG10-TECHS]. Refer also to checkpoint 5.8.

Techniques:

9.3 Provide information to the user about current author-specified input configurations (e.g., keyboard bindings specified in HTML documents with the "accesskey" attribute). [Priority 2] (Checkpoint 9.3)

Techniques:

9.4 Allow the user to change the default input configuration as follows: Allow the user to override any binding that is part of the user agent default input configuration (checkpoint 9.8). The user agent is not required to allow the user to override standard bindings for the operating system (e.g., for access to help). For any binding in the default keyboard configuration, allow the user to override it with a binding of a single key alone or with modifier keys. [Priority 2] (Checkpoint 9.4)
Note: This checkpoint applies to all supported input methods: keyboard, voice, graphical user interface, etc. The override requirement only applies to bindings for the same input method (i.e., the user must be able to override a keyboard binding with another keyboard binding). Refer also to checkpoint 9.5, checkpoint 9.9, checkpoint 9.8, and checkpoint 10.3.

Techniques:

9.5 Allow the user to assign a single-key binding to at least a majority of the functionalities available in the default keyboard configuration (refer to checkpoint 9.8). [Priority 2] (Checkpoint 9.5)
Note: In some modes of interaction (e.g., when the user is entering text), the number of available single keys will be significantly reduced. The number of available single keys will also be determined by the keyboard device capabilities. This checkpoint is an important special case of checkpoint 9.4. Refer also to checkpoint 1.3, checkpoint 9.9, checkpoint 9.8, and checkpoint 10.3.

Techniques:

9.6 Follow operating system conventions to indicate the input configuration. [Priority 2] (Checkpoint 9.6)
Note: For example, on some operating systems, developers may specify which command sequence will activate a functionality so that the standard user interface components display that binding. For example, if a functionality is available from a menu, the letter of the activating key will be underlined in the menu. This checkpoint is an important special case of checkpoint 5.8.

Techniques:

9.7 For the configuration requirements of this document, allow the user to save user preferences in at least one user profile. Allow users to select from among available profiles or no profile (i.e., the user agent default settings). [Priority 2] (Checkpoint 9.7)
Note: The configuration requirements of the checkpoints in this document involve user preferences for styles, presentation rates, input configurations, navigation, viewport behavior, and user agent alerts.

Techniques:

9.8 Ensure that the default input configuration includes bindings for the following functionalities required by other checkpoints in this document: move focus to next active element; move focus to previous active element; activate focused link; search for text; search again for same text; next history state (forward); previous history state (back); increase size of rendered text; decrease size of rendered text; increase global volume; decrease global volume; (each of) stop, pause, resume, fast advance, and fast reverse selected audio, video, and animation. If the user agent supports the following functionalities, the default input configuration must also include bindings for them: enter URI for new resource; add to favorites (i.e., bookmarked resources); view favorites; stop loading resource; reload resource; refresh rendering; forward one viewport; back one viewport; next line; previous line. [Priority 2] (Checkpoint 9.8)

Techniques:

9.9 For graphical user interfaces, allow the user to configure the position of controls on tool bars of the user agent user interface, to select or remove controls for the user interface from a predefined set, and to restore the default user interface. [Priority 3] (Checkpoint 9.9)
Note: This checkpoint is an important special case of checkpoint 9.4.

Techniques:

Guideline 10. Provide accessible product documentation and help.

Checkpoints for accessible documentation:

10.1 Ensure that at least one version of the product documentation conforms to at least Level Double-A of the Web Content Accessibility Guidelines 1.0 [WCAG10]. [Priority 1] (Checkpoint 10.1)

Techniques:

10.2 Document all user agent features that promote accessibility. [Priority 1] (Checkpoint 10.2)
Note: For example, review the documentation or help system to ensure that it includes information about the accessibility requirements of WAI Guidelines.

Techniques:

10.3 Document the default input configuration (e.g., default keyboard bindings). [Priority 1] (Checkpoint 10.3)

Techniques:

The following table shows how one might document keyboard bindings. It shows the default keyboard configuration for versions of Netscape Navigator [NAVIGATOR] running on the Macintosh, Unix, and Windows operating systems. If a function exists in the browser but does not have a binding, its corresponding cell is marked with an asterisk. If the function does not exist, it is left blank. Note: This table lists some, but not all, functionalities and keyboard bindings of Navigator. It is meant to illustrate, not serve as definitive documentation for Netscape Navigator.

Some entries contain links to special notes. The number in parentheses following the link is the number of the relevant note.

Note: To make this table accessible, a linear version of Navigator Keyboard Bindings is available.

Navigator Keyboard Bindings
Function Macintosh (v 4.61) Unix (v 4.51) Windows (v 4.7)
Move within a document
Scroll to next page Page Down Page Down Page Down
Scroll to previous page Page Up Page Up Page Up
Scroll to top * * Control-Home
Scroll to bottom * * Control-End
Move between documents
Open a new document Command+L Alt+O Control+O
Stop loading a document Command+. Esc Esc
Refresh a document Command+R Alt+R Control+R
Load previous document Command+[
or
Command+Left Arrow		 Alt+Left Arrow Alt+Left Arrow
Load next document Command+]
or
Command+Right Arrow		 Alt+Right Arrow Alt+Right Arrow
Navigate elements within a document
Move focus to next frame * * *
Move focus to previous frame * * *
Move focus to next active element (1) Tab Tab Tab
Move focus to previous active element (1) Shift+Tab Shift+Tab Shift+Tab
Find word in page Command+F Alt+F Control+F
Act on HTML elements
Select a link * * Enter
Toggle a check box * * Shift or Enter
Activate radio button * * Shift
Move focus to next item in an option box * * Down Arrow or Right Arrow
Move focus to previous item in an option box * * Up Arrow or Left Arrow
Select item in an option box * * Enter
Press a button (2) Return, Space Enter, Space Enter, Space
Navigate menus
Activate menu * * Alt+ the underlined letter in the menu title
Deactivate menu * Esc Esc
Move focus to next menu item * * (3) Down Arrow
Move focus to previous menu item * * (3) Up Arrow
Select menu item * underlined letter in the menu item Enter
Move focus to submenu * * (3) Right Arrow
Move focus to main menu * * (3) Left Arrow
Navigate bookmarks
View bookmarks menu * (4) * Alt+C+B
Move focus to next item in bookmarks menu Down Arrow (4) * Down Arrow
Move focus to previous item in bookmarks menu Up Arrow (4) * Up Arrow
Select item in bookmarks menu Return (4) * Enter
Add bookmark Command+D Alt+K Control+D
Edit bookmarks Command+B Alt+B Control+B
Delete current bookmark (5) Delete Alt+D Delete
Navigate history list
View history list Command+H Alt+H Control+H
Move focus to next item in history list * * Down Arrow
Move focus to previous item in history list * * Up Arrow
Move focus to first item in history list * * Left Arrow
Select item in history list * * Enter (6)
Close history list Command+W Alt+W Control+W
Define view
Increase font size (7) Shift+Command+] Alt+] Control+]
Decrease font size (7) Shift+Command+[ Alt+[ Control+[
Change font color * * *
Change background color * * *
Turn off author-defined style sheets * * *
Turn on user-defined style sheets (8) ? ? ?
Apply next user-defined style sheet ? ? ?
Apply previous user-defined style sheet ? ? ?
Other functionalities
Access to documentation * * *

Notes.

  1. In Windows, active elements of the user interface include links, text entry boxes, buttons, checkboxes, radio buttons, etc. In Unix and Macintosh, Tab cycles through text entry boxes only.
  2. In Windows, this works for any button, since any button can gain the user interface focus using keyboard commands. In Unix and Macintosh, this only applies to the "Submit" button following a text entry.
  3. In Unix, the menus cannot be opened with binding keys. However, once a menu is opened it stays opened until it is explicitly closed, which means that the menus can still be used with shortcut keys to some extent. Sometimes left and right arrows move between menus and up and down arrows move within menus, but this does not seem to work consistently, even within a single session.
  4. In Macintosh, you cannot explicitly view the bookmarks menu. However, if you choose "Edit Bookmarks", which does have a keyboard binding, you can then navigate through the bookmarks and open bookmarked documents in the current window.
  5. To delete a bookmark you must first choose "Edit Bookmarks" and then move the focus to the bookmark you want to delete.
  6. In Windows, when you open a link from the history menu using Enter, the document opens in a new window.
  7. All three systems have menu items (and corresponding shortcut keys) meant to allow the user to change the font size. However, the menu items are consistently inactive in both Macintosh and Unix. The user seems to be able to actually change the font sizes only in Windows.
  8. It is important to allow users to set their own Cascading Style Sheets. Although Navigator does currently allow the user to override the author's choice of foreground color, background color, font, and font size, it does not allow some of the advanced capabilities that make CSS so powerful. For example, a blind user may want to save a series of style sheets which show only headings, only links, etc., and then view the same page using some or all of these style sheets in order to orient himself to the organization of the page before reading the page.
10.4 In a dedicated section of the documentation, describe all features of the user agent that promote accessibility. [Priority 2] (Checkpoint 10.4)
Note: This is a more specific requirement than checkpoint 10.2.

Techniques:

10.5 In each software release, document all changes that affect accessibility. [Priority 2] (Checkpoint 10.5)
Note: Features that affect accessibility are listed in this document and in platform-specific accessibility guidelines.

Techniques:

3 Accessibility topics

This section presents general accessibility techniques that may apply to more than one checkpoint.

3.1 Access to content

User agents must ensure that users have access to content, either rendered through the user interface or made available to assistive technologies through an API. While providing serial access to a stream of content would satisfy this requirement, this would be analogous to offering recorded music on a cassette: other technologies exist (e.g., CD-ROMs) that allow direct access to music. It is just as important for user agents to allow users to access Web content efficiently, whether the content is being rendered as a two-dimensional graphical layout, an audio stream, or a line-by-line braille stream. Providing efficient access to content involves:

These topics are addressed below.

3.1.1 Preserve and provide structure

When used properly, markup languages structure content in ways that allow user agents to communicate that structure across different renderings. A table describes relationships among cells and headers. Graphically, user agents generally render tables as a two-dimensional grid. However, serial renderings (e.g., speech and braille) must also make those relationships apparent, otherwise users may not understand the purpose of the table and the relationships among its cells (refer to the section on table techniques). User agents must render content in ways that allow users to understand the underlying document structure, which may consist of headings, lists, tables, synchronized multimedia, link relationships, etc. Providing alternative renderings (e.g., an outline view) will also help users understand document structure.

Note: Even though the structure of a language like HTML is defined by a Document Type Definition (DTD), user agents may convey structure according to a "more intelligent" document model when that model is well-known. For instance, in the HTML DTD, heading elements (H1 - H6) do not nest, but presenting the document as nested headings may convey the document's structure more effectively than as a flat list of headers.

3.1.2 Allow access to selected content

The guidelines emphasize the importance of navigation as a way to provide efficient access to content. Navigation allows users to access content more efficiently and when used in conjunction with selection and focus mechanisms, allows users to query content for metadata. For instance, blind users often navigate a document by skipping from link to link, deciding whether to follow each link based on metadata about the link. User agents can help them decide whether to follow a link by allowing them to query each focused link for the link text, title information, information about whether the link has been visited, whether the link involves a fee, etc. While much of this information may be rendered, the information must also be available to assistive technologies.

For example, the Amaya browser/editor [AMAYA] makes available all attributes and their values to the user through a context menu. The user selects an element (e.g., with the mouse) and opens an attribute menu that shows which attributes are available for the element and which are set. The user may read or write values to attributes (since Amaya is an editor). Information about attributes is also available through Amaya's structured view, which renders the document tree as structured text.

The selection may be widened (moved to the nearest node one level up the document tree) by pressing the Escape key; this is a form of structured navigation based on the underlying document object model.

Users may want to select content based on structure alone (as offered by Amaya) but also based on how the content has been rendered. For instance, most user agents allow users to select ranges of rendered text that may cross "element boundaries".

3.1.3 Access to equivalents

Authors provide equivalents to content so that users may understand the function of a page or part of a page even though they may not be able to make use of a particular content type. For example, authors must provide text equivalents for non-text content (e.g., images, video, audio-only presentations, etc.) because text may be rendered as speech or braille and may be used by users with visual or hearing or both disabilities. User agents must ensure that these equivalents are available to users, either through the user interface or through an API.

How authors specify equivalents depends on the markup language used. For information about equivalents for SMIL [SMIL] content, refer to "Accessibility Features of SMIL" [SMIL-ACCESS]. In HTML 4 [HTML4], authors specify equivalents as follows:

Techniques for providing access to equivalents include the following:

3.1.4 Context

Authors and user agents provide context to users through content, structure, navigation mechanisms, and query mechanisms. Titles, dimensions, dates, relationships, the number of elements, and other metadata all help orient the user, particularly when available as text. For instance, user agents can help orient users by allowing them to request that document headings and lists be numbered. Refer also to the section on table techniques, which explains how users agents can offer table navigation and the ability to query a table cell for information about the cell's row and column position, associated header information, etc.

3.2 User control of style

To ensure accessibility, users must be able to configure the style of rendered content and the user interface. Author-specified styles, while important, may make content inaccessible to some users. User agents must allow users to increase the size of rendered text (e.g., with a zoom mechanism or font size control), to change colors and color combinations, to slow down multimedia presentations, etc.

To give authors design flexibility and allow users to control important aspects of content style, user agents should implement CSS ([CSS1], [CSS2]) and allow users to create and apply user style sheets. CSS includes mechanisms for tailoring rendering for a particular output medium, including audio, braille, screen, and print.

3.3 Link techniques

User agents make links accessible by providing navigation to links, helping users decide whether to follow them, and allowing interaction in a device-independent manner. Link techniques include the following:

JAWS for Windows HTML Options menu, which allows configuration of a number of link rendering options

As shown in the following image, JAWS for Windows [JFW] offers a view for configuring a number of rendering features, notably some concerning link types, text link verbosity, image map link verbosity, graphical link verbosity, and internal links.

3.4 List techniques

User agents can make lists accessible by ensuring that list structure – and in particular, embedded list structure – is available through navigation and rendering.

3.5 Table techniques

The HTML TABLE element was designed represent relationships among data ("data" tables). Even when authored well and used according to specification, tables may pose problems for users with disabilities for a number of reasons:

For these situations, user agents may assist these users by providing table navigation mechanisms and supplying context that is present in a two-dimensional rendering (e.g., the cells surrounding a given cell).

To complicate matters, many authors use tables to lay out Web content ("layout" tables). Not only are table structures used to lay out objects on the screen, table elements such as TH (table header) in HTML are used to font styling rather than to indicate a true table header. These practices make it difficult for assistive technologies to rely on markup to convey document structure. Consequently, assistive technologies often must resort to interpreting the rendered content, even though the rendered content has "lost" information encoded in the markup. For instance, when an assistive technology "reads" a table from its graphical rendering, the contents of multiline cells may become intermingled. For example, consider the following table:

This is the top left cell    This is the top right cell 
of the table.                of the table.

This is the bottom left      This is the bottom right 
cell of the table.           cell of the table.

Screen readers that read rendered content line by line would read the table cells incorrectly as "This is the top left cell This is the top right cell". So that assistive technologies are not required to gather incomplete information from renderings, these guidelines require that user agents provide access to document source through an API (refer to checkpoint 5.3).

The following sections discuss techniques for providing improved access to tables.

3.5.1 Table metadata

Users of screen readers or other serial access devices cannot gather information "at a glance" about a two-dimensional table. User agents can make tables more accessible by providing the user with table metadata such as the following:

When navigating, quick access to table metadata will allow users to decide whether to navigate within the table or skip over it. Other techniques:

3.5.2 Linear rendering of tables

A linear rendering of tables -- cells presented one at a time, row by row or column by column -- may be useful, but generally only for simple tables. For more complex tables, user agents need to convey more information about relationships among cells and their headers. A linear rendering of a table can be considered an equivalent for a multi-dimensional table.

Note: The following techniques apply to columns as well as rows. The elements listed in this section are HTML 4.01 table elements ([HTML4], section 11).

3.5.3 Cell rendering

The most important aspect of rendering a table cell is that the cell's contents be rendered faithfully and be identifiable as the contents of a single cell. However, user agents may provide additional information to help orient the user:

3.5.4 Cell header algorithm

Properly constructed data tables distinguish header cells from data cells. How headers are associated with table cells depends on the markup language. The following algorithm is based on the HTML 4.01 algorithm to calculate header information ([HTML4], section 11.4.3). For the sake of brevity, it assumes a left-to-right ordering, but will work for right-to-left tables as well (refer to the "dir" attribute of HTML 4 [HTML4], section 8.2). For a given cell:

3.5.5 Cell header repair strategies

Not all data tables include proper header markup, which the user agent may be able to detect. Some repair strategies for finding header information include the following:

Other repair issues to consider:

3.5.6 Table navigation

To permit efficient access to tables, user agents should allow users to navigate to tables and within tables, to select individual cells, and to query them for information about the cell and the table as a whole.

3.6 Image map techniques

One way to make an image map accessible is to render the links it contains as text links. This allows assistive technologies to render the links a speech or braille, and benefits users with slow access to the Web and users of small Web devices that do not support images but can support hypertext. User agents may allow users to toggle back and forth between a graphical mode for image maps and a text mode.

To construct a text version of an image map in HTML:

Furthermore, user agents that render a text image map instead of an image may preface the text image map with inline metadata such as:

Allow users to suppress, shrink, and expand text versions of image maps so that they may quickly navigate to an image map (which may be, for example, a navigation tool bar) and decide whether to "expand" it and follow the links of the map. The metadata listed above will allow users to decide whether to expand the map. Ensure that the user can expand and shrink the map and navigate its links using the keyboard and other input devices.

3.7 Frame techniques

Frames were originally designed so that authors could divide up graphic real estate and allow the pieces to change independently (e.g., selecting an entry in a table of contents in one frame changes the contents of a second frame). While frames are not inherently inaccessible, they raise some accessibility issues:

To name a frame in HTML, use the following algorithm:

  1. Use the "title" attribute on FRAME, or if not present,
  2. Use the "name" attribute on FRAME, or if not present,
  3. Use title information of the referenced frame source (e.g., the TITLE element of the source HTML document), or
  4. Use title information of the referenced long description (e.g., what "longdesc" refers to in HTML), or
  5. Use frame context (e.g., "Frame 2.1.3" to indicate the path to this frame in nested framesets).

To make frames accessible, user agents should do the following:

Consider renderings of the following document:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
<HTML lang="en">
<HEAD>
  <META http-equiv="Content-Type" 
           content="text/html; charset=iso-8859-1">
  <TITLE>Time Value of Money</TITLE>
</HEAD>

<FRAMESET COLS="*, 388">
  <FRAMESET ROWS="51, *">
    <FRAME src="sizebtn" marginheight="5" marginwidth="1" 
       name="Size buttons" title="Size buttons">
    <FRAME src="outlinec" marginheight="4" marginwidth="4" 
       name="Presentation Outline" 
           title="Presentation Outline">
  </FRAMESET>

  <FRAMESET ROWS="51, 280, *">
    <FRAME src="navbtn" marginheight="5" marginwidth="1" 
       name="Navigation buttons" 
       title="Navigation buttons">
    <FRAME src="slide001" marginheight="0" marginwidth="0" 
      name="Slide Image" title="Slide Image">
    <FRAME src="note001" name="Notes" title="Notes">
  </FRAMESET>
<NOFRAMES> 
<P>List of Presentation Slides</P>
<OL>
<LI><A HREF="slide001">Time Value of Money</A>
<LI><A HREF="slide002">Topic Overview</A>
<LI><A HREF="slide003">Terms and Short Hand</A>
<LI><A HREF="slide004">Future Value of a Single CF</A>
<LI><A HREF="slide005">Example 1: FV example:The
NBA’s new Larry Bird exception</A>
<LI><A HREF="slide006">FV Example: NBA’s Larry
Bird Exception (cont.)</A>
<LI><A HREF="slide007">SuperStar’s Contract
Breakdown</A>
<LI><A HREF="slide008">Present Value of a Single
Cash Flow</A>
<LI><A HREF="slide009">Example 2: Paying Jr, and
A-Rod</A>
<LI><A HREF="slide010">Example 3: Finding Rate of
Return or Interest Rate</A>
<LI><A HREF="slide011">Annuities</A>
<LI><A HREF="slide012">FV of Annuities</A>
<LI><A HREF="slide013">PV of Annuities</A>
<LI><A HREF="slide014">Example 4: Invest Early in
an IRA</A>
<LI><A HREF="slide015">Example 4 Solution</A>
<LI><A HREF="slide016">Example 5: Lotto Fever
</A>
<LI><A HREF="slide017">Uneven Cash Flows: Example
6:Fun with the CF function</A>
<LI><A HREF="slide018">Example 6 CF worksheet inputs</A>
<LI><A HREF="slide019">CF inputs continued</A>
<LI><A HREF="slide020">Non-Annual Interest
Compounding</A>
<LI><A HREF="slide021">Example 7: What rate are
you really paying?</A>
<LI><A HREF="slide022">Nominal to EAR Calculator</A>
<LI><A HREF="slide023">Continuous Interest Compounding</A>
<LI><A HREF="slide024">FV and PV with non-annual
interest compounding</A>
<LI><A HREF="slide025">Non-annual annuities</A>
<LI><A HREF="slide026">Example 8: Finding Monthly
Mortgage Payment</A>
<LI><A HREF="slide027">solution to Example 8</A>
</OL>
</NOFRAMES>
</FRAMESET>
</HTML>

The following examples show how some user agents handle this frameset.

Example frameset with five frame panes rendered in Microsoft Internet Explorer 5.0

Rendering of a frameset by Internet Explorer [IE-WIN].

Rendering by Lynx [LYNX]:

                                        Time Value of Money

   FRAME: Size buttons
   FRAME: Presentation Outline
   FRAME: Navigation buttons
   FRAME: Slide Image
   FRAME: Notes

   List of Presentation Slides
    1. Time Value of Money 
    2. Topic Overview 
    3. Terms and Short Hand 
    4. Future Value of a Single CF 
    5. Example 1: FV example:The NBA's new Larry Bird exception 
    6. FV Example: NBA's Larry Bird Exception (cont.) 
    7. SuperStar's Contract Breakdown 
    8. Present Value of a Single Cash Flow 
    9. Example 2: Paying Jr, and A-Rod 
   10. Example 3: Finding Rate of Return or Interest Rate 
   11. Annuities 
   12. FV of Annuities 
   13. PV of Annuities 
   14. Example 4: Invest Early in an IRA 
   15. Example 4 Solution 
   16. Example 5: Lotto Fever 
   17. Uneven Cash Flows: Example 6:Fun with the CF function 
   18. Example 6 CF worksheet inputs 
   19. CF inputs continued 
   20. Non-Annual Interest Compounding 
   21. Example 7: What rate are you really paying? 
   22. Nominal to EAR Calculator 
   23. Continuous Interest Compounding 
   24. FV and PV with non-annual interest compounding 
   25. Non-annual annuities 
   26. Example 8: Finding Monthly Mortgage Payment 
   27. solution to Example 8

Example frameset with five links for each of the frame elements in IBM home page reader

Rendering of a frameset by Home Page Reader [HPR].

User agents may also indicate the number of frames in a document and which frame is the current frame via the menu bar or popup menus. Users can configure the user agent to include a FRAMES menu item in their menu bar. The menu bar makes the information highly visible to all users and is very accessible to assistive technologies.

A pull down menu indicating the number of frames in a document, the labels associated with each frame, and a check mark to indicate the current frame

In this image of the Accessible Web Browser [AWB], the menu bar indicates the number of frames and uses a check mark next to the name of the current frame.

3.8 Form techniques

To make forms accessible, user agents need to ensure that users may interact with them in a device-independent manner, that users can navigate to the various form controls, and that information about the form and its controls is available on demand.

3.8.1 Form navigation techniques

3.8.2 Form orientation techniques

Provide the following information about forms on demand:

3.8.3 Form control orientation techniques

Provide the following information about the controls in a form on demand (e.g., for the control with focus):

3.8.4 Form submission techniques

Some users do not want forms to be submitted without their consent. The following techniques address user control of form submissions:

3.9 Generated content techniques

User agents may help orient users by generating additional content that "announces" a context change. This may be done through CSS 2 [CSS2] style sheets using a combination of selectors (including the ':before' and ':after' pseudo-elements described in section 12.1) and the 'content' property (section 12.2).

For instance, the user might choose to hear "language:German" when the natural language changes to German and "language:default" when it changes back. This may be implemented in CSS 2 with the ':before' and ':after' pseudo-elements ([CSS2], section 5.12.3)

For example, with the following definition in the stylesheet:

    [lang|=es]:before { content: "start Spanish "; }
    [lang|=es]:after  { content: " end Spanish"; }

the following HTML example:

<P lang="es" class="Spanish">
 <A href="foo_esp.html" 
    hreflang="es">Esta pagina en español</A></P>

might be spoken "start Spanish _Esta pagina en espanol_ end Spanish". Refer also to information on matching attributes and attribute values useful for language matching in CSS 2 ([CSS2], section 5.8.1).

The following example uses style sheets to distinguish visited from unvisited links with color and a text prefix.

The phrase "Visited link:" is inserted before every visited link:

    A:link           { color: red }     /* For unvisited links */
    A:visited        { color: green }   /* For visited links */
    A:visited:before { content: "Visited link: "; }

To hide content, use the CSS 'display' or 'visibility' properties ([CSS2], sections 9.2.5 and 11.2, respectively). The 'display' property suppresses rendering of an entire subtree. The 'visibility' property causes the user agent to generate a rendering structure, but display it invisibly (which means it takes up space, but cannot be seen).

The following XSLT style sheet (excerpted from the XSLT Recommendation [XSLT], Section 7.7) shows how to one might number H4 elements in HTML with a three-part label.

Example.

<xsl:template match="H4">
   <fo:block>
     <xsl:number level="any" from="H1" count="H2"/>
     <xsl:text>.</xsl:text>
     <xsl:number level="any" from="H2" count="H3"/>
     <xsl:text>.</xsl:text>
     <xsl:number level="any" from="H3" count="H4"/>
     <xsl:text> </xsl:text>
     <xsl:apply-templates/>
   </fo:block>
  </xsl:template>

End example.

3.10 Content repair techniques

When generating repair content, user agent developers should consider the following issues:

Refer also the section on table cell header repair strategies. Refer also to the W3C document "Techniques For Accessibility Evaluation And Repair Tools" [AERT].

3.11 Script and applet techniques

User agents must make dynamic content accessible to users who may be disoriented by changes in content, who may have a physical disability that prevents them from interacting with a document within a time interval specified by the author, or whose user agent does not support scripts or applets. Not only must user agents make available equivalents to dynamic content, they must allow users to turn off scripts, to stop animations, adjust timing parameters, etc.

3.11.1 Script techniques

Certain elements of a markup language may have associated event handlers that are triggered when certain events occur. User agents must be able to identify those elements with event handlers statically associated (i.e., associated in the document source, not in a script). In HTML 4 ([HTML4], section 18.2.3), intrinsic events are specified by the attributes beginning with the prefix "on": "onblur", "onchange", "onclick", "ondblclick", "onkeydown", "onkeypress", "onkeyup", "onload", "onmousedown", "onmousemove", "onmouseout", "onmouseover", "onmouseup", "onreset", "onselect", "onsubmit", and "onunload".

Techniques for providing access to scripts include the following:

3.11.2 Applet techniques

When a user agent loads an applet, it should support the Java system conventions for loading an assistive technology (refer to the appendix on loading assistive technologies for DOM access). If the user is accessing the applet through an assistive technology, the assistive technology should alert the user when the applet receives content focus as this will likely result in the launch of an associated plug-in or browser-specific Java Virtual Machine. The user agent then needs to turn control of the applet over to the assistive technology. User agents must make equivalents available to the assistive technology. Applets generally include an application frame that provides title information.

3.12 Input configuration techniques

Many people benefit from direct access to important user agent functionalities (e.g., via a single key stroke or short voice command): users with poor physical control (who might mistakenly repeat a key stroke), users who fatigue easily (for whom key combinations involve significant effort), users who cannot remember key combinations, and any user who wants to operate the user agent efficiently.

User agents that allow users to modify default input configurations must account for configuration information from several sources: user agent defaults, user preferences, author-specified configurations, and operating system conventions. In HTML, the author may specify keyboard bindings with the "accesskey" attribute ([HTML4], section 17.11.2). Users generally specify their preferences through the user interface but may also do so programmatically or through a profile. The user agent may also consider user preferences set at the operating system level.

To the user, the most important information is the final configuration once all sources have been cascaded (combined) and all conflicts resolved. Knowing the default configuration is also important; checkpoint 10.3 requires that the default configuration be documented. The user may also want to know how the current configuration differs from the default configuration and what configuration in the current viewport comes from the author. This information may also be useful to technical support personnel who may be assisting users.

3.12.1 Resolution of input configuration conflicts

In general, user preferences should override other configurations, however this may not always be desirable. For example, users should be prevented from configuring the user agent in a way that would interfere with important functionalities such as quitting the user agent or reconfiguring it.

Some possible options user agents may make available to the user to resolve conflicts include:

3.12.2 Invocation through the input configuration

Users may want to use a keyboard or voice binding to shift focus without actually triggering the associated functionality (refer to parallel behavior described for navigation of active elements in the section on sequential navigation techniques). First-time users may want to access additional information before deciding whether to activate a control. More experienced users or those familiar with a page may want to select and activate in one step. Therefore, the user agent may provide the user with the following options:

  1. On invocation of the input binding, move focus to the associated active element, but do not activate it.
  2. On invocation of the input binding, move focus to the associated active element and prompt the user with information that will allow the user to decide whether to activate the element (e.g., link title or text). Allow the user to suppress future prompts for this particular input binding.
  3. On invocation of the input binding, move focus to the associated active element and activate it.

3.13 Speech techniques

The following techniques apply to user agents that render content as synthesized speech. For information about speech recognition and accessibility, refer to "Speak to Write" [SPEAK2WRITE]. For more information about voice browser technology developed at W3C, refer to "Voice Browsers: An introduction and glossary for the requirements drafts" [VOICEBROWSER].

3.14 Techniques for reducing dependency on spatial interactions

Some interactions with content may require spatial information, often provided by users without disabilities through a pointing device such as a mouse. User agents should should not require users to "move through space" to interact with content (or "time", for that matter; refer to checkpoint 2.2). Thus, for users without a pointing device, the user agent's first approximation of access, say through the keyboard, would be to simulate the mouse with keystrokes. However, such a technique usually requires a significant amount of visual feedback as well as physical dexterity, both of which may not be possible for users with some disabilities. A better alternative is to allow users to enter coordinates where a click should occur. While this is "direct access" to the coordinate, this requires extensive knowledge of the geometry in question. A still better alternative is to allow the user to interact with "objects" in content at a more abstract level than geometry. For example, most HTML authors can use "client-side" image maps rather than "server-side" since what is important is not the actual coordinates but rather that the user has selected one region instead of another. The user agent should convey information about the regions, using descriptions provided by the author. Instead of having users select a state of the United States by its precise longitude and latitude, it is just as possible to allow them to select state by name.

4 Appendix: Accessibility features of some operating systems

Several operating systems now include built-in accessibility features designed to assist individuals with varying abilities. Despite operating systems differences, the built-in accessibility features use a similar naming convention and offer similar functionalities, within the limits imposed by each operating system (or particular hardware platform). The following is a list of built-in accessibility features from several platforms:

StickyKeys
StickyKeys allows users who have difficulties with pressing several keys simultaneously to press and release sequentially each key of the configuration.
MouseKeys
These allow users to move the mouse cursor and activate the mouse button(s) from the keyboard.
RepeatKeys
RepeatKeys allows users to set how fast a key repeats ("repeat rate") when the key is held pressed. It also allows users to control how quickly the key starts to repeat after the key has been pressed ("delay until repeat"). Users can also turn off key repeating.
SlowKeys
SlowKeys instructs the computer not to accept a key as pressed until it has been pressed and held down for more than a user-configurable length of time.
BounceKeys
BounceKeys prevents extra characters from being typed if the user bounces (e.g., due to a tremor) on the same key when pressing or releasing it.
ToggleKeys
ToggleKeys provides an audible indication for the status of keys that have a toggled state (keys that maintain status after being released). The most common toggling keys include Caps Lock, Num Lock, and Scroll Lock.
SoundSentry
SoundSentry monitors the operating system and applications for sounds in order to provide a graphical indication when a sound is being played. Older versions of SoundSentry may have flashed the entire display screen for example, while newer versions of SoundSentry provide the user with a selection of options, such as flashing the active window or flashing the active window caption bar.

The next three built-in accessibility features are not as commonly available as the above group of features, but are included here for definition, completeness, and future compatibility.

ShowSounds
ShowSounds are user settings or software switches that cause audio to be presented using both audio and graphics. Applications may use these switches as the basis of user preferences.
HighContrast
HighContrast sets fonts and colors designed to make the screen easier to read.
TimeOut
TimeOut turns off built-in accessibility features automatically if the computer remains idle for a user-configurable length of time. This is useful for computers in public settings such as a library. TimeOut might also be referred to as "reset" or "automatic reset".

The next accessibility feature listed here is not considered to be a built-in accessibility feature (since it only provides an alternate input channel) and is presented here only for definition, completeness, and future compatibility.

SerialKeys
SerialKeys allows a user to perform all keyboard and mouse functions from an external assistive device (such as communication aid) communicating with the computer via a serial character stream (e.g., serial port, infra-red port, etc.) rather than or in conjunction with, the keyboard, mouse, and other standard input devices/methods.

Microsoft Windows 95, Windows 98, and Window NT 4.0

To find out about built-in accessibility features on Windows platforms, ask the system via the "SystemParametersInfo" function. Please refer to "Software accessibility guidelines for Windows applications" [MS-ENABLE] for more information.

For information about Microsoft keyboard configurations (Internet Explorer, Windows 95, Windows 98, and more), refer to documentation on keyboard assistance for Internet Explorer and MS Windows [MS-KEYBOARD].

The following accessibility features can be adjusted from the Accessibility Options Control Panel:

Additional accessibility features available in Windows 98:

Magnifier
Magnifier is a windowed, screen enlargement and enhancement program used by people with low vision to magnify an area of the graphical display (e.g., by tracking the text cursor, current focus, etc.). Magnifier can also invert the colors used by the system within the magnification window.
Accessibility Wizard
The Accessibility Wizard is a setup tool to assist users with the configuration of system accessibility features.

Apple Macintosh operating system

The following accessibility features can be adjusted from the Easy Access Control panel. Note: The Apple naming convention for accessibility features is to put spaces between the terms (e.g., "Sticky Keys" instead of "StickyKeys").

The following accessibility features can be adjusted from the Keyboard Control Panel.

The following accessibility feature can be adjusted from the Sound or Monitors and Sound Control Panel (depending on system version).

Additional accessibility features available for the Macintosh OS:

CloseView
CloseView is a full screen, screen enlargement and enhancement program used by people with low vision to magnify the information on the graphical display, and it can also change the colors used by the system.
SerialKeys
SerialKeys is available as freeware from Apple and several other Web sites.

AccessX, X Keyboard Extension (XKB), and the X Window System

The following accessibility features can be adjusted from the AccessX graphical user interface X client on some DEC, SUN, and SGI operating systems. Other systems supporting XKB may require the user to manipulate the features via a command line parameter(s).

Note: AccessX became a supported part of the X Window System X Server with the release of the X Keyboard Extension in version X11R6.1

DOS (Disk Operating System)

The following accessibility features are available from a freeware program called AccessDOS, which is available from several Internet Web sites including IBM, Microsoft, and the Trace Center, for either PC-DOS or MS-DOS versions 3.3 or higher.

5 Appendix: Loading assistive technologies for access to the document object model

Many of the checkpoints in the guidelines require a "host" user agent to communicate information about content and the user interface to assistive technologies. This appendix explains how developers can ensure the timely exchange of this information (refer to checkpoint 5.6). The techniques described here include:

  1. Loading the entire assistive technology in the address space of the host user agent;
  2. Loading part of the assistive technology in the address space of the host user agent (e.g., piece of stub code, a dynamically linked library (DLL), a browser helper object, etc.);
  3. Out-of-process access to the document object model.

The first two techniques are similar, differing in the amount of, or capability of, the assistive technology loaded in the same process or address space as the host user agent. These techniques are likely to provide faster access to the document object model since they will not be subject to inter-process communication overhead.

Note: This appendix does not address specialized user agents (e.g., pwWebSpeak [PWWEBSPEAK]).

Loading assistive technologies for direct navigation of the document object model

First, the host user agent needs to know which assistive technology to load. One technique for this is to store a reference to an assistive technology in a system registry file or, in the case of Java, a properties file. Registry files are common among many operating system platforms:

Here is an example entry for Java:

    assistive_technologies=com.ibm.sns.svk.AccessEngine

In Microsoft Windows, a similar technique could be followed by storing the name of a Dynamic Link Library (DLL) for an assistive technology in a designated assistive technology key name/assistive technology pair.

Here is an example entry for Windows:

    HKEY_LOCAL_MACHINE\Software\Accessibility\DOM 
           "ScreenReader, VoiceNavigation"

Attaching the assistive technologies to the document object model

Once the assistive technology has been registered, any other user agent can determine whether it needs to be loaded and then load it. Once loaded, the assistive technology can monitor the document object model as needed.

On a non-Java platform, a technique to do this would be to create a separate thread with a reference to the document object model using a DLL. This new thread will load the DLL and call a specified DLL entry name with a pointer to the document object model interface. The assistive technology process will then run as long as required.

The assistive technology has the option to either:

In the future, it will be necessary to provide a more comprehensive reference to the application that not only provides direct navigation to its client area document object model, but also multiple document object models that it is processing and an event model for monitoring them.

Java's direct access

Java can facilitate timely access to accessibility components. In this example, an assistive technology running on a separate thread monitors user interface events such as focus changes. When focus changes, the assistive technology is alerted of which component object has focus. The assistive technology can communicate directly with all components in the application by walking the parent/child hierarchy and connecting to each component's methods and monitor events directly. In this case, an assistive technology has direct access to component specific methods as well as those provided for by the Java Accessibility API. There is no reason that a document object model interface to user agent components could not be provided via Java.

In Java 1.1.x, Sun's Java access utilities load an assistive by monitoring the Java awt.properties file for the presence of assistive technologies and loads them as shown in the following code example:

import java.awt.*;
import java.util.*;
      
String atNames = Toolkit.getProperty("AWT.assistive_technologies",null);
if (atNames != null) {
    StringTokenizer parser = new StringTokenizer(atNames," ,");
    String atName;
    while (parser.hasMoreTokens()) {
       atName = parser.nextToken();
       try {
          Class.forName(atName).newInstance();
       } 
       catch (ClassNotFoundException e) {
          throw new AWTError("Assistive Technology not found: " + atName);
       } 
       catch (InstantiationException e) {
          throw new AWTError("Could not instantiate Assistive" + 
                             " Technology: " + atName);
       } 
       catch (IllegalAccessException e) {
          throw new AWTError("Could not access Assistive" + 
                             " Technology: " + atName);
       } catch (Exception e) {
          throw new AWTError("Error trying to install Assistive" + 
                             " Technology: " + atName + " " + e);
       }
    }
}

In the above code example, the function Class.forName(atName).newInstance() creates a new instance of the assistive technology. The constructor for the assistive technology will then be responsible for monitoring application component objects by monitoring system events.

In the following code example, the constructor for the assistive technology, AccessEngine, adds a focus change listener using Java accessibility utilities. When the assistive technology is alerted that an object has received focus, it has direct access to that object. If the Object, o, has implemented a document object model interface, the assistive technology will have direct access to the document object model in the same process space as the application.

   import java.awt.*;
   import javax.accessibility.*;
   import com.sun.java.accessibility.util.*;
   import java.awt.event.FocusListener;

   class AccessEngine implements FocusListener {
      public AccessEngine() {
         //Add the AccessEngine as a focus change listener
         SwingEventMonitor.addFocusListener((FocusListener)this);
      }
      
      public void focusGained(FocusEvent theEvent) {
         // get the component object source
         Object o = theEvent.getSource();
         // check to see if this is a document object model component
         if (o instanceof DOM) {
            ...
         }
      }
      public void focusLost(FocusEvent theEvent) {
         // Do Nothing
      }
   }

In this example, the assistive technology has the option of running stand-alone or acting as a cache for a bridge that communicates with a main assistive technology running outside the Java virtual machine.

Loading part of the assistive technologies for direct access to the document object model

In order to attach to a running instance of Internet Explorer 4.0, you can use a Browser Helper Object ([BHO]), which is a DLL that will attach itself to every new instance of Internet Explorer 4.0 [IE-WIN] (only if you explicitly run iexplore.exe). You can use this feature to gain access to the object model of Internet Explorer and to monitor events. This can be tremendously helpful when many method calls need to be made to IE, as each call will be executed much more quickly than the out of process case.

There are some requirements when creating a Browser Helper Object:

Java access bridge

To provide native Microsoft Windows assistive technologies access to Java applications without creating a Java native solution, Sun Microsystems provides the "Java Access Bridge." This bridge is loaded as an assistive technology as described in the section on loading assistive technologies for direct navigation of the document object model. The bridge uses a Java Native Invocation (JNI) to Dynamic Link Library (DLL) communication and caching mechanism that allows a native assistive technology to gather and monitor accessibility information in the Java environment. In this environment, the assistive technology determines that a Java application or applet is running and communicates with the Java Access Bridge DLL to process accessibility information about the application/applet running in the Java Virtual Machine.

Loading assistive technologies for indirect access to the document object model

Access to application specific data across process boundaries or address space might be costly in terms of performance. However, there are other reasons to consider when accessing the document object model that might lead a developer to wish to access it from their own process or memory address space. One obvious protection this method provides is that, if the user agent fails, it does not disable the user's assistive technology as well. Another consideration would be legacy systems, where the user relies on their assistive technology for access to software other than the user agent, and thus would have their application loaded all the time.

There are several ways to gain access to the user agent's document object model. Most user agents support some kind of external interface, or act as a mini-server to other applications running on the desktop. Internet Explorer [IE-WIN] is a good example of this, as IE can behave as a component object model (COM) server to other applications. Mozilla [MOZILLA], the open source release of Navigator also supports cross platform COM (XPCOM).

The following example illustrates the use of COM to access the IE object model. This is an example of how to use COM to get a pointer to the WebBrowser2 module, which in turn enables access to an interface/pointer to the document object, or IE document object model for the content.

   /* first, get a pointer to the WebBrowser2 control */
   if (m_pIE == NULL) {
      hr = CoCreateInstance(CLSID_InternetExplorer, 
           NULL, CLSCTX_LOCAL_SERVER, IID_IWebBrowser2, 
           (void**)&m_pIE);

      /* next, get a interface/pointer to the document in view, 
         this is an interface to the document object model (DOM)*/

      void CHelpdbDlg::Digest_Document() {
         HRESULT hr;
         if (m_pIE != NULL) {
            IDispatch* pDisp;
            hr = m_pIE->QueryInterface(IID_IDispatch, (void**) &pDisp);
            if (SUCCEEDED(hr)) {
        
               IDispatch* lDisp;
               hr = m_pIE->get_Document(&lDisp);
               if (SUCCEEDED(hr)) {
           
                   IHTMLDocument2* pHTMLDocument2;
                   hr = lDisp->QueryInterface(IID_IHTMLDocument2,
                               (void**) &pHTMLDocument2);
                   if (SUCCEEDED(hr)) {
            
                   /* with this interface/pointer, IHTMLDocument2*,
                      you can then work on the document */
                      IHTMLElementCollection* pColl;
                      hr = pHTMLDocument2->get_all(&pColl);
                      if (SUCCEEDED(hr)) {
                    
                         LONG c_elem;
                         hr = pColl->get_length(&c_elem);
                         if (SUCCEEDED(hr)) {
                            FindElements(c_elem, pColl);
                         }
                         pColl->Release();
                      }
                      pHTMLDocument2->Release();
                   }
                   lDisp->Release();
               }
               pDisp->Release();
            }
         }
      }
   }

For a working example of this method, refer to HelpDB [HELPDB].

6 Glossary

Active element
An active element is an element with behaviors that may be activated (or "triggered") either through the user interface or through an API (e.g., by using scripts). Some element instances may be active at times but not at others (e.g., they may be "deactivated" through scripts, or they may only active for a period of time determined by the author). Which elements are active depends on the document language and whether the features are supported by the user agent. In HTML 4 [HTML4] documents, for example, active elements include links, image maps, form controls, element instances with a value for the "longdesc" attribute, and element instances with scripts (event handlers) explicitly associated with them (e.g., through the various "on" attributes). Most systems use the content focus to navigate active elements and identify which is to be activated. An active element's behavior may be triggered through any number of mechanisms, including the mouse, keyboard, an API, etc. The effect of activation depends on the element. For instance, when a link is activated, the user agent generally retrieves the linked Web resource. When a form control is activated, it may change state (e.g., check boxes) or may take user input (e.g., a text entry field). Refer also to the definition of event handler.
Alert
In this document, "to alert" means to make the user aware of some event, without requiring acknowledgement. For example, the user agent may alert the user that new content is available on the server by displaying a text message in the user agent's status bar. Refer to checkpoint 1.5 for requirements about alerts.
Application Programming Interface (API), standard input/output/device API
An application programming interface (API) defines how communication may take place between applications.

As part of encouraging interoperability, this document recommends using standard APIs where possible, although this document does not define in all cases how those APIs are standardized (i.e., whether they are defined by specifications such as W3C Recommendations, defined by an operating system vendor, de facto standards, etc.). Implementing APIs that are independent of a particular operating system (e.g., the W3C DOM Level 2 specifications) may reduce implementation costs for multi-platform user agents and promote the development of multi-platform assistive technologies. Implementing standard APIs defined for a particular operating system may reduce implementation costs for assistive technology developers who wish to interoperate with more than one piece of software running on that operating system.

A "device API" defines how communication may take place with an input or output device such as a keyboard, mouse, video card, etc. A "standard device API" is one that is considered standard for that particular device on a given operating or windowing system.

In this document, an "input/output API" defines how applications or devices communicate with a user agent. As used in this document, input and output APIs include, but are not limited to, device APIs (and in general, they define a more abstract communication interface than device APIs). A "standard input/output API" is one that is expected to be implemented by software running on a particular operating system. Standard input/output APIs may vary from system to system. For example, on desktop computers today, the standard input APIs are for the mouse and keyboard. For touch screen devices or mobile devices, standard input APIs may include stylus, buttons, voice, etc. The graphical display and sound card are considered standard ouput devices for a graphical desktop computer environment, and each has a standard API.

Assistive technology
In the context of this document, an assistive technology is a user agent that:
  1. relies on services (such as retrieving Web resources, parsing markup, etc.) provided by one or more other "host" user agents. Assistive technologies communicate data and messages with host user agents by using and monitoring APIs.
  2. provides services beyond those offered by the host user agents to meet the requirements of a users with disabilities. Additional services include alternative renderings (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, content transformations (e.g., to make tables more accessible), etc.

For example, screen reader software is an assistive technology because it relies on browsers or other software to enable Web access, particularly for people with visual and learning disabilities.

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

Beyond this document, assistive technologies consist of software or hardware that has been specifically designed to assist people with disabilities in carrying out daily activities, e.g., wheelchairs, reading machines, devices for grasping, text telephones, vibrating pagers, etc.
Attribute
This document uses the term "attribute" in the XML sense: an element may have a set of attribute specifications (refer to the XML 1.0 specification [XML] section 3).
Audio, Audio object
An audio object is output from an audio viewport.
Audio-only presentation
An audio-only presentation is a presentation consisting exclusively of one or more audio tracks presented concurrently or in series. Examples of an audio-only presentation include a musical performance, a radio-style news broadcast, and a book reading.
Audio track
An audio track is an audio object that is intended as a whole or partial presentation. An audio track can, but does not necessarily correspond to a single audio channel (left or right audio channel).
Auditory description
An auditory description is either a prerecorded human voice or a synthesized voice (recorded or generated dynamically) describing the key visual elements of a movie or animation. The auditory description is synchronized with the audio track of the presentation, usually during natural pauses in the audio track. Auditory descriptions include information about actions, body language, graphics, and scene changes.
Author styles
Authors styles are style property values that come from a document, its associated style sheets, or are generated by the server.
Captions
Captions (or sometimes "closed captions") are text transcripts that are synchronized with other audio or visual tracks. Captions convey information about spoken words and non-spoken sounds such as sound effects. They benefit people who are deaf or hard-of-hearing, and anyone who cannot hear the audio (e.g., someone in a noisy environment). Captions are generally rendered graphically above, below, or superimposed over video. Note: Other terms that include the word "caption" may have different meanings in this document. For instance, a "table caption" is a title for the table, often positioned graphically above or below the table. In this document, the intended meaning of "caption" will be clear from context.
Collated text transcript
A collated text transcript is a text equivalent of a movie or animation. More specifically, it is the combination of the text transcript of the audio track and the text equivalent of the visual track. For example, a collated text transcript typically includes segments of spoken dialogue interspersed with text descriptions of the key visual elements of a presentation (actions, body language, graphics, and scene changes). Refer also to the definitions of text transcript and auditory description. Collated text transcripts are essential for individuals who are deaf-blind.
Configure and Control
In the context of this document, both the terms "control" and "configure" share in common the idea of governance such as a user may exercise over interface layout, user agent behavior, rendering style, and other parameters required by this document. Generally, the difference in the terms centers on the idea of persistence. When a user makes a change by "controlling" a setting, that change usually does not persist beyond that user session. On the other hand, when a user "configures" a setting, that setting typically persists into later user sessions. Furthermore, the term "control" typically means that the change can be made easily (such as through a keyboard shortcut) and that the results of the change occur immediately, whereas the term "configure" typically means that making the change requires more time and effort (such as making the change via a series of menus leading to a dialog box, via style sheets or scripts, etc.) and that the results of the change may not take effect immediately (e.g., due to time spent reinitializing the system, initiating a new session, rebooting the system). In order to be able to configure and control the user agent, the user must be able to "read" as well as "write" values for these parameters. Configuration settings may be stored in a profile. The range and granularity of the changes that can be controlled or configured by the user may depend on system or hardware limitations.

Both configuration and control may apply at different "levels": across Web resources (i.e., at the user agent level, or inherited from the system), to the entirety of a Web resource, or to components of a Web resource (e.g., on a per-element basis). For example, users may configure the user agent to apply the same font family across Web resources, so that all text is displayed by default using that font family. Or, the user may wish to configure the rendering of a particular element type, which may be done through style sheets. Or, the user may wish to control the text size dynamically (zooming in and out) for a given document, without affecting the Web resource-level configuration. Or, the user may wish to control the text size dynamically for a given element, e.g., by navigating to the element and zooming in on it.

Note: In this document, the noun "control" means "user interface component" or "form component".

Content
In this specification, the term "content" is used in three ways:
  1. Content refers to the document object as a whole or in parts.
  2. Content refers to the content of an HTML or XML element, in the sense employed by the XML 1.0 specification ([XML], section 3.1): "The text between the start-tag and end-tag is called the element's content." Context should indicate that the term content is being used in this sense.
  3. Content is used in the context of the phrases non-text content and text content.
Device-independence
Device-independence refers to the ability to make use of software with any supported input or output device. User agents should follow operating system conventions and use standard system APIs for input and output.
Document Object, Document Object Model
In general usage, the term "document object" refers to the user agent's representation of data (e.g., a document). This data generally comes from the document source, but may also be generated (from style sheets, scripts, transformations, etc.), produced as a result of preferences set within the user agent, added as the result of a repair performed automatically by the user agent, etc. Some data that is part of the document object is routinely rendered (e.g., in HTML, what appears between the start and end tags of elements and the values of attributes such as "alt", "title", and "summary"). Other parts of the document object are generally processed by the user agent without user awareness, such as DTD-defined names of element types and attributes, and other attribute values such as "href", "id", etc. These guidelines require that users have access to both types of data through the user interface.

A "document object model" is the abstraction that governs the construction of the user agent's document object. The document object model employed by different user agents may vary in implementation and sometimes in scope. This specification requires that user agents implement the APIs defined in the "Document Object Model (DOM) Level 2 Specification" ([DOM2CORE], [DOM2HTML], [DOM2STYLE]) for access to HTML, XML, and CSS content. These DOM APIs allow authors to access and modify the content via a scripting language (e.g., JavaScript) in a consistent manner across different scripting languages. As a standard interface, the DOM APIs make it easier not just for authors, but for assistive technology developers to extract information and render it in ways most suited to the needs of particular users. The relevant W3C DOM Recommendations are listed in the references.

Document source, Document source view
In this document, the term "document source" refers to the data that the user agent receives as the direct result of a request for a Web resource (e.g., as the result of an HTTP/1.1 [RFC2616] "GET", as the result of opening a local resource, etc.). A "document source view" generally renders the document source as text written in the markup language(s) used to build it. The document source is generally a subset of the document object (e.g., since the document object may include repair content).
Documentation
Documentation refers to all information provided by the vendor about a product, including all product manuals, installation instructions, the help system, and tutorials.
Element
This document uses the term "element" both in the XML sense (an element is a syntactic construct as described in the XML 1.0 specification [XML], section 3) and more generally to mean a type of content (such as video or sound) or a logical construct (such as a header or list).
Equivalent (for content)
In the context of this document, an equivalency relationship between two pieces of content means that one piece -- the "equivalent" -- is able to serve essentially the same function for a person with a disability (at least insofar as is feasible, given the nature of the disability and the state of technology) as the other piece -- the "equivalency target" -- does for a person without any disability. For example, the text "The Full Moon" might convey the same information as an image of a full moon when presented to users. If the image is part of a link and understanding the image is crucial to guessing the link target, then the equivalent must also give users an idea of the link target. Thus, an equivalent is provided to fulfill the same function as the equivalency target.

Equivalents include text equivalents (e.g., text equivalents for images; text transcripts for audio tracks; collated text transcripts for multimedia presentations and animations) and non-text equivalents (e.g., a prerecorded auditory description of a visual track of a movie, or a sign language video rendition of a written text, etc.). Please refer to the definitions of text content and non-text content for more information.

Each markup language defines its own mechanisms for specifying equivalents. For instance, in HTML 4 [HTML4] or SMIL 1.0 [SMIL], authors may use the "alt" attribute to specify a text equivalent for some elements. In HTML 4, authors may provide equivalents (or portions of equivalents) in attribute values (e.g., the "summary" attribute for the TABLE element), in element content (e.g., OBJECT for external content it specifies, NOFRAMES for frame equivalents, and NOSCRIPT for script equivalents), and in prose. Please consult the Web Content Accessibility Guidelines 1.0 [WCAG10] and its associated Techniques document [WCAG10-TECHS] for more information about equivalents.
Events and scripting, event handler
User agents often perform a task when an event occurs that is due to user interaction (e.g., document loading, mouse motion or a key press), a request from the operating system, etc. Some markup languages allow authors to specify that a script, called an event handler, be executed when the event occurs. Note: The combination of HTML, style sheets, the Document Object Model (DOM) and scripting is commonly referred to as "Dynamic HTML" or DHTML. However, as there is no W3C specification that formally defines DHTML, this document only refers to event handlers and scripts.
Explicit user request
In several checkpoints in this document, the term "explicit user request" is used to mean any user interaction recognized with certainty to be for a specific purpose. For instance, when the user selects "New viewport" in the user agent's user interface, this is an explicit user request for a new viewport. On the other hand, it is not an explicit request when the user activates a link and that link has been marked up by the author to open a new viewport (since the user may not know that a new viewport will open). Nor is it an explicit user request even if the link text states "will open a new viewport". Some other examples of explicit user requests include "yes" responses to prompts from the user agent, configuration through the user agent's user interface, activation of known form submit controls, and link activation (which should not be assumed to mean more than "get this linked resource", even if the link text or title or role indicates more). Some examples of behaviors that happen without explicit user request include changes due to scripts. Note: Users make mistakes. For example, a user may submit a form inadvertently by activating a known form submit control. In this document, this type of mistake is still considered an explicit user request.
Focus, content focus, user interface focus, current focus
The notion of focus refers to two identifying mechanisms of user agents:
  1. The "content focus" designates an active element in a document. A viewport has at most one content focus.
  2. The "user interface focus" designates a control of the user interface that will respond to user input (e.g., a radio button, text box, menu, etc.).
In this document, the term "focus" by itself encompasses both types of focus. Where one is meant specifically in this document, it is identified.

When several viewports coexist, each may have a content and user interface focus. At all times, only one content focus or one user interface focus is active, called the current focus. The current focus responds to user input and may be toggled between content focus and user interface focus through the keyboard, pointing device, etc. Both the content and user interface focus may be highlighted. Refer also to the definition of point of regard.

Graphical
In this document, the term "graphical" refers to information (text, colors, graphics, images, animations, etc.) rendered for visual consumption.
Highlight
In this document, "to highlight" means to emphasize through the user interface. For example, user agents highlight which content is selected or focused and which viewport is the current viewport. Graphical highlight mechanisms include dotted boxes, underlining, and reverse video. Synthesized speech highlight mechanisms include alterations of voice pitch and volume.
Input configuration
An input configuration is the mapping of user agent functionalities to some user interface trigger mechanisms (e.g., menus, buttons, keyboard keys, voice commands, etc.). The default input configuration is the mapping the user finds after installation of the software; it must be part of the user agent documentation (per checkpoint 10.3]).
Multimedia Presentation
For the purposes of this document, a multimedia presentation is a presentation that is not a visual-only presentation, audio-only presentation, or tactile-only presentation. In a "classic" multimedia presentation (e.g., a movie that has sound track or an animation with accompanying audio), at least one visual track is closely synchronized with at least one audio track.
Natural language
Natural language is spoken, written, or signed human language such as French, Japanese, and American Sign Language. On the Web, the natural language of content may be specified by markup or HTTP headers. Some examples include the "lang" attribute in HTML 4 ([HTML4] section 8.1), the "xml:lang" attribute in XML 1.0 ([XML], section 2.12), the HTML 4 "hreflang" attribute for links in HTML 4 ([HTML4], section 12.1.5), the HTTP Content-Language header ([RFC2616], section 14.12) and the Accept-Language request header ([RFC2616], section 14.4).
Point of regard
The point of regard is a position in rendered content that the user is presumed to be viewing. The dimensions of the point of regard may vary. For example, it may be a point (e.g., a moment in an audio rendering or a cursor in a graphical rendering), or a range of text (e.g., focused text), or a two-dimensional area (e.g., content rendered through a two-dimensional graphical viewport). The point of regard is almost always within a viewport (though the dimensions of the point of regard could exceed those of the viewport). The point of regard may also refer to a particular moment in time for content that changes over time (e.g., an audio-only presentation). User agents may use the focus, selection, or other means to designate the point of regard. A user agent should not change the point of regard unexpectedly as this may disorient the user.
Presentation
In this document, the term presentation refers to a collection of information, consisting of one or more Web resources, intended to be rendered simultaneously, and identified by a single URI. In general, a presentation has an inherent time component (i.e., it's not just a static "Web page" (refer to the definition of "Web page" in "Web Characterization Terminology and Definitions Sheet" [WEBCHAR]).
Profile
A profile is a named and persistent representation of user preferences that may be used to configure a user agent. Preferences include input configurations, style preferences, etc. On systems with distinct user accounts, profiles enable users to reconfigure software quickly when they log on, and they may be shared by several users. Platform-independent profiles are useful for those who use the same user agent on different platforms.
Prompt
In this document, "to prompt" means to require input from the user. The user agent should allow users to configure how they wish to be prompted. For instance, for a user agent functionality X, configurations might include: always do X without prompting me, never do X without prompting me, don't ever do X but tell me when you could have done X but didn't, don't ever do X and don't tell me, etc.
Properties, values, and defaults
A user agent renders a document by applying formatting algorithms and style information to the document's elements. Formatting depends on a number of factors, including where the document is rendered: on screen, on paper, through speakers, on a braille display, on a mobile device, etc. Style information (e.g., fonts, colors, voice inflection, etc.) may come from the elements themselves (e.g., certain font and phrase elements in HTML), from style sheets, or from user agent settings. For the purposes of these guidelines, each formatting or style option is governed by a property and each property may take one value from a set of legal values. Generally in this document, the term "property" has the meaning defined in CSS 2 ([CSS2], section 3). A reference to "styles" in this document means a set of style-related properties.
The value given to a property by a user agent when it is installed is called the property's default value.
Recognize
A user agent is said to recognize a piece of information when the user agent developer has designed it to handle that information. A user agent recognizes those features of markup or style languages that it implements and the behavior of the user interface controls that it provides. User agents may not understand everything the author has encoded in content, such as the semantics of XML elements unknown to the user agent, whether the link text and link title accurately describe the linked resource, whether a sentence (that has not been specially marked up) is a text equivalent for an image, or whether a script is calculating a factorial. A user agent does not recognize everything that a script does, even though it may implement the scripting language. However, it will recognize some information encoded in scripts, such as code to open a viewport or retrieve a resource from the Web. The Techniques document [UAAG10-TECHS] lists some markup known to affect accessibility that should be recognized by user agents.
Rendered content
The rendered content is that part of content rendered in a given viewport (whether visual, auditory, or tactile).
Repair content, repair text
In this document, the term "repair content" refers to content generated by the user agent in order to correct an error condition or as the result of a user preference. "Repair text" means repair content consisting only of text. This document does not require user agents to include repair content in the document object.

Some error conditions that may lead to the generation of repair content include:

Some user preferences may change content, such as when the user has turned off support for images and a placeholder icon to appears in place of each image that has not been loaded.

For more information about repair techniques for Web content and software, refer to "Techniques For Accessibility Evaluation And Repair Tools" [AERT].

Selection, current selection
The selection generally identifies a range of content (e.g., text, images, etc.) in a document. The selection may be structured (based on the document tree) or unstructured (e.g., text-based). Content may be selected through user interaction, scripts, etc. The selection may be used for a variety of purposes: for cut and paste operations, to designate a specific element in a document, to identify what a screen reader should read, etc.

The selection may be set by the user (e.g., by a pointing device or the keyboard) or through an application programming interface (API). A viewport has at most one selection (though the selection may be rendered graphically as discontinuous text fragments). When several viewports coexist, each may have a selection, but only one is active, called the current selection.

On the screen, the selection may be highlighted using colors, fonts, graphics, magnification, etc. The selection may also be rendered as inflected speech, for example.

Support, implement, conform
In this document, the terms "support", "implement", and "conform" all refer to what a developer has designed a user agent to do, but they represent different degrees of specificity. A user agent "supports" general classes of objects, such as "images" or "Japanese". A user agent "implements" a specification (e.g., the PNG and SVG image format specifications, a particular scripting language, etc.) or an API (e.g., the DOM API) when it has been programmed to follow all or part of a specification. A user agent "conforms to" a specification when it implements the specification and satisfies its conformance criteria. This document includes some explicit conformance requirements (e.g., to a particular level of the "Web Content Accessibility Guidelines 1.0" [WCAG10]).
Synchronize
In this document, "to synchronize" refer to the time-coordination of two or more presentation components (e.g., in a multimedia presentation, a visual track with captions). For Web content developers, the requirement to synchronize means to provide the data that will permit sensible time-coordinated rendering by a user agent. For example, Web content developer can ensure that the segments of caption text are neither too long nor too short, and that they map to segments of the visual track that are appropriate in length. For user agent developers, the requirement to synchronize means to present the content in a sensible time-coordinated fashion under a wide range of circumstances including technology constraints (e.g., small text-only displays), user limitations (slow reading speeds, large font sizes, high need for review or repeat functions), and content that is sub-optimal in terms of accessibility.
Text content, non-text content, text element, non-text element, text equivalent, non-text equivalent
In this document, the term "text element" means content that, when rendered, is understandable in each of three modes to three reference groups:
  1. visually-displayed text, for users who are deaf and adept in reading visually-displayed text;
  2. synthesized speech, for users who are blind and adept in use of synthesized speech;
  3. braille, for users who are deaf-blind and adept at reading braille.

In these definitions, a text element is said to be "understandable" when it fulfills its communication function to representatives of the three reference groups. Furthermore, these definitions make assumptions such as the availability of appropriate hardware and software, that content represents a general mix of purposes (information, education, entertainment, commerce), that the individuals in the groups are able to understand the natural language of the content, that the individuals in the groups are not required to have specialized skills (e.g., computer science degree), etc.

A text element may contain markup for style (e.g., font size or color), structure (e.g., heading levels), and other semantics. However, the essential function of the text element should be retained even if style information happens to be lost in rendering. In this document, the term "text content" refers to content that is composed of one or more text elements. A "non-text element" is an element that fails to be understandable when rendered in any of three modes to their respective reference disability audiences. Thus, text elements have essential accessibility advantages often associated with text while non-text elements are those that lack one or more such advantages.

In this document, the term "non-text content" refers to content that is composed of one or more non-text elements. Per checkpoint 1.1 of "Web Content Accessibility Guidelines 1.0" [WCAG10], authors must provide a text equivalent for every author-supplied non-text element. Similarly, user agent developers must provide a text equivalent for every non-text element offered by the user agent to the user (refer to checkpoint 1.5).

Note that the terms "text element" and "non-text element" are defined by the characteristics of their output (e.g., rendering) rather than those of their input (e.g., information sources) or their internals (e.g., format). For example, in principle, a text element can be generated or encoded in any fashion as long as it has the proper output characteristics. In general, text elements are composed of text (i.e., a sequence of characters). Both text elements and non-text elements should be understood as "pre-rendering" content in contrast to the "post-rendering" content that they produce.

A "text equivalent" is a text element that, when rendered, serves essentially the same function as some other content (i.e., an equivalency target) does for a person without any disability. Similarly, a "non-text equivalent" is a non-text element that, when rendered, serves essentially the same function as the equivalency target does for a person without any disability. Please refer also to the definition of equivalent.

Text transcript
A text transcript is a text equivalent of audio information (e.g., an audio-only presentation or the audio track of a movie or animation). It provides text for both spoken words and non-spoken sounds such as sound effects. Text transcripts make audio information accessible to people who have hearing disabilities and to people who cannot play the audio. Text transcripts are usually pre-written but may be generated on the fly (e.g., by speech-to-text converters). Refer also to the definitions of captions and collated text transcripts.
Tactile object
A tactile object is output from a tactile viewport. Tactile objects include text (rendered as braille) and graphics (rendered as raised-line drawings).
Tactile-only presentation
A tactile-only presentation is a presentation consisting exclusively of one or more tactile tracks presented concurrently or in series.
Tactile track
A tactile track is a tactile object that is intended as a whole or partial presentation. This does not necessarily correspond to a single physical or logical track on the storage or delivery media.
User agent
In this document, the term "user agent" is used in two ways:
  1. Any software that retrieves and renders Web content for users. This may include Web browsers, media players, plug-ins, and other programs -- including assistive technologies -- that help in retrieving and rendering Web content.
  2. The subject of a conformance claim to "User Agent Accessibility Guidelines 1.0" [UAAG10]. This is the most common use of the term in this document and is the usage in the checkpoints.
Text
In this document, the term "text" used by itself refers to a sequence of characters from a markup language's document character set (e.g., Unicode or ISO 10646). Refer to the "Character Model for the World Wide Web " [CHARMOD] for more information about text and characters. Note: This document makes use of other terms that include the word "text" that have highly specialized meanings: collated text transcript, non-text content, text content, non-text element, text element, text equivalent, and text transcript.
User agent default styles
User agent default styles are style property values applied in the absence of any author or user styles. Some markup languages specify a default rendering for documents in that markup language. Other specifications may not specify default styles. For example, XML 1.0 [XML] does not specify default styles for XML documents. HTML 4 [HTML4] does not specify default styles for HTML documents, but the CSS 2 [CSS2] specification suggests a sample default style sheet for HTML 4 based on current practice.
User interface
For the purposes of this document, user interface includes both:
  1. the "user agent user interface", i.e., the controls and mechanisms offered by the user agent for user interaction, such as menus, buttons, keyboard access, etc.
  2. the "content user interface", i.e., the active elements that are part of content, such as form controls, links, applets, etc.
The document distinguishes them only where required for clarity.
User styles
User styles are style property values that come from user interface settings, user style sheets, or other user interactions.
Visual object
A visual object is output from a visual viewport. Visual objects include graphics, text, and visual portions of movies and animations.
Visual-only presentation
A visual-only presentation is a presentation consisting exclusively of one or more visual tracks presented concurrently or in series.
Visual track
A visual track is a visual object that is intended as a whole or partial presentation. A visual track does not necessarily correspond to a single physical or software object. A visual track can be text-based or graphic, static or animated.
Views, viewports, and current viewport
User agents may handle different types of content: markup language, sound, video, etc. The user views rendered content through a viewport, which may be a window, a frame, a piece of paper, a speaker, a virtual magnifying glass, etc. A viewport may contain another viewport (e.g., nested frames). Viewports do not include user interface controls such as prompts, menus, alerts, etc.

The viewport that contains both the current focus and the current selection is called the current viewport. The current viewport is generally highlighted when several viewports coexist. A user agent must provide mechanisms for accessing all content that can be presented by each viewport (e.g., scrolling mechanisms, advance and rewind, etc.).

User agents may render the same content in a variety of ways; each rendering is called a view. For instance, a user agent may allow users to view an entire document or just a list of the document's headers. These are two different views of the document.
Web resource
The term "Web resource" is used in this document in accordance with Web Characterization Terminology and Definitions Sheet [WEBCHAR] to mean anything that can be identified by a Uniform Resource Identifier (URI) as defined in RFC 2396 [RFC2396].

7 References

For the latest version of any W3C specification please consult the list of W3C Technical Reports at http://www.w3.org/TR. Some documents listed below may have been superseded since the publication of this document.

[AERT]
"Techniques For Accessibility Evaluation And Repair Tools", C. Ridpath, W. Chisholm, eds., 26 April 2000. This W3C Working Draft is http://www.w3.org/TR/2000/WD-AERT-20000426.
[ATAG10]
"Authoring Tool Accessibility Guidelines 1.0", J. Treviranus, C. McCathieNevile, I. Jacobs, and J. Richards, eds., 3 February 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-ATAG10-20000203.
[ATAG10-TECHS]
"Techniques for Authoring Tool Accessibility Guidelines 1.0", J. Treviranus, C. McCathieNevile,, I. Jacobs, and J. Richards, eds., 4 May 2000. This W3C Note is http://www.w3.org/TR/2000/NOTE-ATAG10-TECHS-20000504/.
[CHARMOD]
"Character Model for the World Wide Web", M. Dürst, 29 November 1999. This W3C Working Draft is http://www.w3.org/TR/1999/WD-charmod-19991129/
[CSS-ACCESS]
"Accessibility Features of CSS", I. Jacobs, J. Brewer, 4 August 1999. This W3C Note is http://www.w3.org/1999/08/NOTE-CSS-access-19990804.
[CSS1]
"CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds., 17 December 1996, revised 11 January 1999. This W3C Recommendation is http://www.w3.org/TR/1999/REC-CSS1-19990111.
[CSS2]
"CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C. Lilley, and I. Jacobs, eds., 12 May 1998. This W3C Recommendation is http://www.w3.org/TR/1998/REC-CSS2-19980512.
[DOM2CORE]
"Document Object Model (DOM) Level 2 Core Specification", M. Davis, A. Le Hors, P. Le Hégaret, J. Robie, L. Wood, eds., 27 September 2000. This W3C Proposed Recommendation is http://www.w3.org/TR/2000/PR-DOM-Level-2-Core-20000927.
[DOM2EVENTS]
Document Object Model (DOM) Level 2 Events Specification, V. Pixley, ed., 27 September 2000. This W3C Proposed Recommendation is http://www.w3.org/TR/2000/PR-DOM-Level-2-Events-20000927.
[DOM2HTML]
"Document Object Model (DOM) Level 2 HTML Specification", A. Le Hors, P. Le Hégaret, eds., 27 September 2000. This W3C Proposed Recommendation is http://www.w3.org/TR/2000/PR-DOM-Level-2-HTML-20000927
[DOM2RANGE]
Document Object Model (DOM) Level 2 Traversal and Range Specification, V. Apparao, M. Champion, J. Kesselman, J. Robie, P. Sharpe, eds., 27 September 2000. This W3C Proposed Recommendation is http://www.w3.org/TR/2000/PR-DOM-Level-2-Traversal-Range-20000927.
[DOM2STYLE]
"Document Object Model (DOM) Level 2 Style Specification", V. Apparao, P. Le Hégaret, C. Wilson, eds., 27 September 2000. This W3C Proposed Recommendation is http://www.w3.org/TR/2000/PR-DOM-Level-2-Style-20000927.
[HTML4]
"HTML 4.01 Recommendation", D. Raggett, A. Le Hors, and I. Jacobs, eds., 24 December 1999. This W3C Recommendation is http://www.w3.org/TR/1999/REC-html401-19991224.
[MATHML]
"Mathematical Markup Language", P. Ion and R. Miner, eds., 7 April 1998. This W3C Recommendation is http://www.w3.org/TR/1998/REC-MathML-19980407.
[MICROPAYMENT]
"Common Markup for micropayment per-fee-links", T. Michel, ed., 25 August 1999. This W3C Working Draft is http://www.w3.org/TR/1999/WD-Micropayment-Markup-19990825.
[PNG]
"PNG (Portable Network Graphics) Specification 1.0", T. Boutell, ed., 1 October 1996. This W3C Recommendation is http://www.w3.org/TR/REC-png.
[RFC2396]
"Uniform Resource Identifiers (URI): Generic Syntax", T. Berners-Lee, R. Fielding, L. Masinter, August 1998.
[RFC2616]
"Hypertext Transfer Protocol -- HTTP/1.1, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee, June 1999.
[SMIL]
"Synchronized Multimedia Integration Language (SMIL) 1.0 Specification", P. Hoschka, ed., 15 June 1998. This W3C Recommendation is http://www.w3.org/TR/1998/REC-smil-19980615.
[SMIL-ACCESS]
"Accessibility Features of SMIL", M-R. Koivunen, I. Jacobs, 21 September 1999. This W3C Note is http://www.w3.org/TR/1999/NOTE-SMIL-access-19990921.
[SVG]
"Scalable Vector Graphics (SVG) 1.0 Specification", J. Ferraiolo, ed., 2 August 2000. This W3C Candidate Recommendation is http://www.w3.org/TR/2000/CR-SVG-20000802/.
[SVG-ACCESS]
"Accessibility Features of SVG", C. McCathieNevile and M.-R. Koivunen, 7 August 2000. This W3C Note is http://www.w3.org/TR/2000/NOTE-SVG-access-20000807.
[UAAG10]
"Techniques for User Agent Accessibility Guidelines 1.0", J. Gunderson, I. Jacobs, eds. The latest draft of the guidelines is available at http://www.w3.org/TR/UAAG10-TECHS/.
[UAAG10-TECHS]
"Techniques for User Agent Accessibility Guidelines 1.0", J. Gunderson, I. Jacobs, eds. The latest draft of the techniques document is available at http://www.w3.org/TR/UAAG10-TECHS/.
[VOICEBROWSER]
"Voice Browsers: An introduction and glossary for the requirements drafts", M. Robin, J. Larson, 23 December 1999. This document is http://www.w3.org/TR/1999/WD-voice-intro-19991223. This document includes references to additional W3C specifications about voice browser technology.
[WCAG10]
"Web Content Accessibility Guidelines 1.0", W. Chisholm, G. Vanderheiden, and I. Jacobs, eds., 5 May 1999. This W3C Recommendation is http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505.
[WCAG10-TECHS]
"Techniques for Web Content Accessibility Guidelines 1.0", W. Chisholm, G. Vanderheiden, and I. Jacobs, eds. This W3C Note is http://www.w3.org/TR/1999/WAI-WEBCONTENT-TECHS-19990505.
[WEBCHAR]
"Web Characterization Terminology and Definitions Sheet", B. Lavoie, H. F. Nielsen, eds., 24 May 1999. This is a W3C Working Draft that defines some terms to establish a common understanding about key Web concepts. This W3C Working Draft is http://www.w3.org/1999/05/WCA-terms/01.
[XHTML10]
"XHTML[tm] 1.0: The Extensible HyperText Markup Language", S. Pemberton, et al., 26 January 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-xhtml1-20000126.
[XLINK]
"XML Linking Language (XLink) Version 1.0", S. DeRose, E. Maler, D. Orchard, B. Trafford, eds., 3 July 2000. This XML 1.0 Candidate Recommendation is http://www.w3.org/TR/2000/CR-xlink-20000703/.
[XML]
"Extensible Markup Language (XML) 1.0", T. Bray, J. Paoli, C.M. Sperberg-McQueen, eds., 10 February 1998. This W3C Recommendation is http://www.w3.org/TR/1998/REC-xml-19980210.
[XMLSTYLE]
"Associating Style Sheets with XML documents Version 1.0", J. Clark, ed., 29 June 1999. This W3C Recommendation is http://www.w3.org/1999/06/REC-xml-stylesheet-19990629/
[XSLT]
"XSL Transformations (XSLT) Version 1.0", J. Clark, 16 November 1999. This W3C Recommendation is http://www.w3.org/TR/1999/REC-xslt-19991116.

8 Resources

Note: W3C does not guarantee the stability of any of the following references outside of its control. These references are included for convenience. References to products are not endorsements of those products.

8.1 Operating system and programming guidelines

[APPLE-HI]
Refer to the following guidelines from Apple:
[BHO]
Browser Helper Objects: The Browser the Way You Want It, D. Esposito, January 1999. Refer also to http://support.microsoft.com/support/kb/articles/Q179/2/30.asp.
[ED-DEPT]
"Requirements for Accessible Software Design", US Department of Education, version 1.1 March 6, 1997.
[EITAAC]
"EITAAC Desktop Software standards", Electronic Information Technology Access Advisory (EITAAC) Committee.
[IBM-ACCESS]
"Software Accessibility", IBM Special Needs Systems.. Refer to the IBM guidelines for software accessibility, IBM guidelines for Java accessibility.
[ICCCM]
"The Inter-Client communication conventions manual". A protocol for communication between clients in the X Window system.
[ICE-RAP]
"An ICE Rendezvous Mechanism for X Window System Clients", W. Walker. A description of how to use the ICE and RAP protocols for X Window clients.
[JAVA-ACCESS]
"IBM Guidelines for Writing Accessible Applications Using 100% Pure Java", R. Schwerdtfeger, IBM Special Needs Systems.
[JAVA-CHECKLIST]
"Java Accessibility Guidelines and Checklist". IBM Special Needs Systems.
[JAVA-TUT]
"The Java Tutorial. Trail: Creating a GUI with JFC/Swing". An online tutorial that describes how to use the Swing Java Foundation Class to build an accessible user interface. Refer also to information on the Java Foundation Classes.
[JAVAAPI]
Information on Java Accessibility API can be found at Java Accessibility Utilities.
[MOTIF]
The OSF/Motif Style Guide.
[MS-ENABLE]
Software accessibility guidelines for Windows applications. Refer also to Built-in accessibility features.
[MS-KEYBOARD]
Information on keyboard assistance for Internet Explorer and MS Windows.
[MS-SOFTWARE]
"The Microsoft Windows Guidelines for Accessible Software Design". Note: This page summarizes the guidelines and includes links to the full guidelines in various formats (including plain text).
[MSAA]
Information on active accessibility can be found at the Microsoft Active Accessibility home page.
[NISO]
National Information Standards Organization. One activity pursued by this organization concerns Digital Talking Books. Refer to the "Digital Talking Book Features List" and "Digital Talking Book Standards Committee Document Navigation Features List" drafts for more information.
[NOTES-ACCESS]
"Lotus Notes Accessibility Guidelines" IBM Special Needs Systems.
[PHOTO-RDF]
"Describing and retrieving photos using RDF and HTTP", Y. Lafon and B. Bos. The 3 May 2000 version of the W3C Note is http://www.w3.org/TR/2000/NOTE-photo-rdf-20000503.
[SAMI]
Information on Synchronized Accessible Multimedia Interchange (SAMI) accessibility.
[SUN-DESIGN]
Articles, Talks, and Papers from Sun Microsystems about accessibility.
[SUN-HCI]
"Towards Accessible Human-Computer Interaction", Eric Bergman, Earl Johnson, Sun Microsytems 1995. A substantial paper, with a valuable print bibliography.
[TRACE-EZ]
"EZ ACCESS(tm) for electronic devices V 2.0 implementation guide", C. M. Law, G. C. Vanderheiden, 23 February 2000. This guide, developed by the Trace Research and Development Center, describes a simple set of interface enhancements that can be applied to electronic devices so that they can be used by people with disabilities, or anyone who experiences difficulty using a device in the standard method of operation.
[TRACE-REF]
"Application Software Design Guidelines" compiled by G. Vanderheiden. A thorough reference work.
[WHAT-IS]
"What is Accessible Software", James W. Thatcher, Ph.D., IBM, 1997. This paper, available at the IBM Accessibility Center, gives a short example-based introduction to the difference between software that is accessible, and software that can be used by some assistive technologies.
[XGUIDELINES]
Information on accessibility guidelines for Unix and X Window applications. The Open Group has various guides that explain the Motif and Common Desktop Environment (CDE) with topics like how users interact with Motif/CDE applications and how to customize these environments. Note: In X, the terms client and server are used differently from their use when discussing the Web.

8.2 User agents and other tools

A list of alternative Web browsers (assistive technologies and other user agents designed for accessibility) is maintained at the WAI Web site.

[ALTIFIER]
The Altifier Tool generates "alt" text intelligently.
[AMAYA]
Amaya is W3C's test-bed browser and editor.
[AWB]
The Accessible Web Browser senior project at the University of Illinois Champaign-Urbana.
[CSSVALIDATOR]
W3C's CSS Validator service.
[DIRECTDOM]
DirectDom technology, available from alphaWorks, allows a Java developer to manipulate the live Document Object Model of a browser or Scalable Vector Graphics plugin to build rich graphical user interfaces.
[G2]
The G2 player version 7 for Windows.
[HELPDB]
HelpDB is a test tool for Web table navigation.
[HPR]
Home Page Reader.
[IE-WIN]
Internet Explorer 5.0 for Windows 95, Windows 98, and Windows NT. Refer also to information on using COM with IE. Refer also to information about monitoring HTML events in the IE document object model.
[JFW]
JAWS for Windows.
[LYNX]
The Lynx Browser.
[MOZILLA]
The Mozilla browser.
[NAVIGATOR]
Netscape Navigator.
[OPERA]
The Opera Browser.
[PWWEBSPEAK]
pwWebSpeak.
[QUICKTIME]
The Quicktime player.
[TABLENAV]
A table navigation script from the Trace Research Center.
[VALIDATOR]
W3C's HTML/XML Validator service.
[WINDOWEYES]
Window-Eyes.
[WINVISION]
Winvision.

8.3 Accessibility resources

[BRAILLEFORMATS]
"Braille Formats: Principles of Print to Braille Transcription 1997" .
[NBA]
The National Braille Association.
[NBP]
The National Braille Press.
[RFBD]
Recording for the Blind and Dyslexic.
[SAPI]
Microsoft's Speech Application Programming Interface.
[SPEAK2WRITE]
Speak to Write is a site about using speech recognition to promote accessibility.

8.4 Standards resources

[ISO639]
"Codes for the representation of names of languages", ISO 639:1988. For more information, consult http://www.iso.ch/cate/d4766.html. Refer also to http://www.oasis-open.org/cover/iso639a.html.
[UNICODE]
The Unicode Consortium. "The Unicode Standard, Version 3.0", Reading, MA, Addison-Wesley Developers Press, 2000. ISBN 0-201-61633-5. Refer also to http://www.unicode.org/unicode/standard/versions/.

9 Acknowledgments

The active participants of the User Agent Accessibility Guidelines Working Group who authored this document were: James Allan, Denis Anson (College Misericordia), Kitch Barnicle, Harvey Bingham, Dick Brown (Microsoft), Al Gilman, Jon Gunderson (Chair of the Working Group, University of Illinois, Urbana-Champaign), Eric Hansen (Educational Testing Service), Ian Jacobs (Team Contact, W3C), Marja-Riitta Koivunen, Tim Lacy (Microsoft), Charles McCathieNevile (W3C), Mark Novak, David Poehlman, Mickey Quenzer (isSound), Gregory Rosmaita (Visually Impaired Computer Users Group of New York City), Madeleine Rothberg, and Rich Schwerdtfeger.

Many thanks to the following people who have contributed through review and past participation in the Working Group: Paul Adelson, Olivier Borius, Judy Brewer, Bryan Campbell, Kevin Carey, Tantek Çelik, Wendy Chisholm, David Clark, Chetz Colwell, Wilson Craig, Nir Dagan, Daniel Dardailler, B. K. Delong, Neal Ewers, Geoff Freed, John Gardner, Larry Goldberg, Glen Gordon, John Grotting, Markku Hakkinen, Earle Harrison, Chris Hasser, Kathy Hewitt, Philipp Hoschka, Masayasu Ishikawa, Phill Jenkins, Earl Johnson, Jan Kärrman (for help with html2ps), Leonard Kasday, George Kerscher, Peter Korn, Josh Krieger, Catherine Laws, Greg Lowney, Susan Lesch, Scott Luebking, William Loughborough, Napoleon Maou, Peter Meijer, Karen Moses, Masafumi Nakane, Charles Oppermann, Mike Paciello, David Pawson, Michael Pederson, Helen Petrie, Michael Pieper, Jan Richards, Hans Riesebos, Joe Roeder, Lakespur L. Roca, Lloyd Rutledge, Liam Quinn, T.V. Raman, Robert Savellis, Constantine Stephanidis, Jim Thatcher, Jutta Treviranus, Claus Thogersen, Steve Tyler, Gregg Vanderheiden, Jaap van Lelieveld, Jon S. von Tetzchner, Willie Walker, Ben Weiss, Evan Wies, Chris Wilson, Henk Wittingen, and Tom Wlodkowski.

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