User Agent Accessibility Guidelines 1.0
W3C Working Draft 1 September 2000
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- Latest version:
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- Editors:
- Ian Jacobs, W3C
Jon Gunderson, University of Illinois at
Urbana-Champaign
- 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.
The guidelines in this document explain to developers how to design user agents that are accessible to people with
disabilities. User agents include graphical
desktop browsers, multimedia players, text browsers, voice browsers, plug-ins,
and other assistive
technologies that provide access to Web
content. While these guidelines primarily address the accessibility
of mainstream graphical user agents, the principles presented apply to other
types of user agents as well. Following these principles will help make the Web
accessible to users with disabilities and will benefit all users.
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 release of the document incorporates minimal requirements for each
checkpoint as discussed by the Working Group. The Working Group has not yet
established minimal requirements for all of the checkpoints.
A history of
changes to this document is available on the Web.
Note: Three checkpoints in this document (checkpoint 5.1, checkpoint 5.2, and checkpoint 5.7) refer to the W3C
DOM Level 2
[DOM2] specification, which is a Candidate Recommendation as of 1
September 2000. The User Agent Accessibility Guidelines Working Group continues
to track the progress of that specification and expects to maintain its
dependency on DOM Level 2 if that specification advances to Proposed
Recommendation before the Working Group has resolved its open issues. At its 25
April 2000 teleconference, the Working Group resolved that it may modify the
checkpoints in question to depend on DOM 1 if that will accelerate the progress
of this document.
Publication as a Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or obsoleted
by other documents at any time. It is inappropriate to cite W3C Working Drafts
as other than "work in progress."
Please send comments about this document 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 Working
Group are described in the charter. A list of the
Working Group
participants is available.
A list of current W3C Recommendations and
other technical documents can be found at the W3C Web site.
A separate document, entitled "Techniques for User Agent Accessibility
Guidelines 1.0" [UAAG10-TECHS], provides
suggestions and examples of how each checkpoint might be satisfied. It also
includes references to other accessibility resources (such as platform-specific
software accessibility guidelines) that provide additional information on how a
user agent may satisfy each checkpoint. Readers are strongly encouraged to
become familiar with the Techniques document. Note that the techniques provided
are informative examples only, and other strategies may be used to meet the
checkpoint as well as, or in place of, those listed therein. The Techniques
document is expected to be updated more frequently than the current
guidelines.
"User Agent Accessibility Guidelines 1.0" is part of a series of
accessibility guidelines published by the Web
Accessibility Initiative (WAI). This document explains the
responsibilities of user agent developers in making the Web accessibility to
users with disabilities. The series also includes "Web Content Accessibility
Guidelines 1.0"
[WCAG10], which explains the responsibilities of authors, and
"Authoring Tool Accessibility Guidelines 1.0" [ATAG10], which explains the
responsibilities of authoring tool developers. The WAI also makes available other
resources and educational materials promoting Web accessibility.
This introduction (section 1) provides context for understanding the
guidelines listed in section 2. Section 1 explains
the benefits of accessible user agent design and the principles of accessible user agent design behind the
guidelines. Section 3 explains how to make claims that
software conforms to these guidelines and details about the applicability
of the requirements to different kinds of user agents.
For those unfamiliar with accessibility issues pertaining to user agent
design, consider that many users with disabilities may be accessing the Web in
contexts very different from your own:
- Users may not be able to see, hear, move, or may not be able to process
some types of information easily or at all.
- Users may have difficulty reading or comprehending text.
- Users may not have or be able to use a keyboard or mouse.
User agents must be designed to take into account the diverse requirements
of users with disabilities. This document specifies requirements that user agent developers must satisfy to ensure
accessibility of the user agent.
Software that follows the guidelines in this document will not only benefit
users with disabilities, it will be more flexible, manageable, extensible, and
beneficial to all users. Many users browse the Web with requirements similar to
those of users with disabilities. For instance:
- They may have a text-only screen, a small screen, or a slow Internet
connection (e.g., via a mobile phone browser). These users will benefit from
the same features that provide access to people with low vision or
blindness.
- They may be in a situation where their eyes, ears, or hands are busy or
interfered with (e.g., driving to work, working in a noisy environment, etc.).
These users will benefit from the same features that provide access to people
who cannot use a mouse or keyboard due to a visual or physical disability.
- They may not understand fluently the natural language of spoken content.
These users may benefit from the same text
equivalents that make spoken language accessible to people with a
hearing disability.
The guidelines in this document describe some basic principles of accessible
design. As the previous examples illustrate, accessible design generally
benefits all users.
This document is organized according to several principles that, if
followed, will improve the design of any type of user agent.
A user with a disability must have access to all the functionalities offered
by the user agent through its user
interface:
- Since some users cannot use some parts of the user interface, it needs to
be adaptable to their particular needs. To ensure the accessibility of the user
interface, people with disabilities should be involved in its design and
testing.
- One requirement is that users be able to operate the user interface with a
variety of input devices (mouse, keyboard, speech input, etc.) and output
devices (graphical
display, speech output, Braille display, etc.). Redundant input and output
methods (accomplished through the standard input and output Application
Programming Interfaces (APIs) implemented by the user agent) help users
operate controls of the user agent as well as those included as part of content.
- The user agent installation procedure needs to be accessible otherwise the
user will not be able to use it at all. Most of the requirements in this
document should be adopted for the installation procedure to ensure its
accessibility.
This document includes a number of user interface requirements that are
similar to, or related to, general guidelines for user interface design. The
general topic of user interface design for computer software exceeds the scope
of this document, though some user interface requirements have been included
because of their importance to accessibility. The Techniques document
[UAAG10-TECHS] includes some references to general software design
guidelines and platform-specific accessibility guidelines.
Note: This document includes some requirements for user
agent support of some authoring practices that may be discouraged (e.g., for
reasons of accessibility or by languages specifications themselves) but that
may be widely deployed.
User agents must ensure access to
content:
- By ensuring access to all text, video, sound, and other content, including
equivalent alternatives for content (e.g.,
"alt" attribute values in HTML, external long descriptions, etc.) and
relationships among content (e.g., table cells and their headers).
- By allowing users to configure
content
rendering parameters (text size, colors, synthesized speech rate and
volume, etc.).
- By allowing users to navigate the content (e.g., with scrollbars,
navigation of active
elements, navigation according to structure, etc.).
- By making Web content and user agent information available to assistive
technology through standard APIs.
User agents can help the user remain oriented in a page or site by supplying
context, including:
- Browsing context. This includes information about the number of frames, the
title of the current frame, whether loading for a page or video clip has
finished or stalled, etc. Graphical
clues about browsing context (such as frames, proportional scroll bars, a
visually
highlighted selection, etc.) help some, but not all users, so the
context information must be available in a device-independent manner.
- Element context. This includes information about specific elements (e.g.,
the dimensions of a table, the length of an audio clip, the structure of a
form, etc.) and surrounding information. For instance, users who are blind and
who may navigate by jumping from link to link on a page or presentation will
benefit from nearby information that helps them decide quickly whether to
follow the link, as well as from metadata about the link: whether it has been
visited, the type of the target resource, the length of an audio or video clip
that will be started, whether activating the link involves a fee, etc.
The user agent should also minimize chances that user will become
disoriented. User agents should:
- For changes to the content or
viewport that the user does not initiate, allow
the user to request notification when these changes occur (e.g., when a
viewport opens, a script is executed, etc.).
- Allow the user to return to a known state (e.g., by providing browsing
history mechanism).
Following platform and operating system standards and guidelines promotes
accessibility, usability, and predictability:
- Platform guidelines explain what users will expect from the look and feel
of the user interface, keyboard conventions, documentation, etc. Platform
guidelines also include information about accessibility features that the user
agent should adopt rather than reimplementing them.
- So that desktop browsers can make information available to assistive
technologies, they must communicate through standard interfaces. An
architecture that makes possible programmatic access to
content and the user
interface will benefit assistive technologies, scripting tools, and
automated test engines. It will also promote software modularity and
reuse.
The eleven guidelines in this document state general principles for the
development of accessible user agents. Each guideline includes:
- The guideline number.
- The statement of the guideline.
- The rationale behind the guideline and identification of some groups of
users who benefit from it.
- A list of checkpoint definitions. This list may be split into groups of
related checkpoints. For instance, the list might be split into one group of
"checkpoints for content accessibility" and a second group of "checkpoints for
user interface accessibility". Within each group, checkpoints are ordered
according to their priority, e.g., Priority 1 before
Priority 2.
Each checkpoint definition includes:
- The checkpoint number.
- The statement of the checkpoint. The statement of the checkpoint is one or
more requirements that must be met by the subject of a
conformance claim. For readability, the checkpoints refer to a single "user
agent", but the subject of the conformance claim
may consist of several software components.
- The priority of the checkpoint.
- Informative notes about the checkpoint. These notes include examples, cross
references, and commentary to help readers understand the scope of the
checkpoint. Note: Some checkpoints in this document are more
general than others, and some may overlap in scope. Special case checkpoints
that identify important accessibility requirements are clearly labeled.
- A link to a corresponding section of "Techniques for User Agent
Accessibility Guidelines 1.0" [UAAG10-TECHS], where the
checkpoint is examined in detail, including information about implementation
and examples.
Each checkpoint has been designed to express clearly a minimal requirement
for accessibility. This document and "Techniques for User Agent Accessibility
Guidelines 1.0" [UAAG10-TECHS] both suggest
how users agents may go beyond satisfying minimal requirements to promote
accessibility, but user agents are only required to satisfy the minimal
requirements expressed by the checkpoints. Note: In some
cases, though the requirement of a checkpoint may be clear, without
documentation from vendors (e.g., about APIs they implement), it may be difficult to
verify that a user agent has satisfied the requirement.
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.
Since people use a variety of devices for input and output, user agent
developers must ensure redundancy in the
user interface. A conforming user agent that is accessing content
that conforms to the Web Content Accessibility Guidelines 1.0 [WCAG10] should
be able to render all Web content through each of at least three modalities --
visually-displayed text, synthesized speech, and Braille -- subject, to the
limitations the applicability provisions of this
document. That is why text messages are generally accessible -- they may be
used by people with graphical displays, speech synthesizers, or Braille
displays.
People who cannot or do not use a mouse must be able to operate the user
interface with the keyboard, through voice input, a head wand, touch screen, or
other device. Keyboard operation of all functionalities offered
through the user interface is one of the most important aspects of user agent
accessibility on almost every platform. The keyboard is available to most
users, it is widely supported, and hooks provided for the keyboard can be used
for other types of input.
To ensure that assistive
technologies can both operate the user agent programmatically (e.g.,
through simulated keyboard events) and monitor user agent output (e.g., output
text), developers are expected to use each API appropriately. Developers should not, for
example, pre-rasterize text or convert text to a series of strokes since doing
so may prevent assistive technologies from being able to render the text as
speech or Braille.
Checkpoints for communication with other software:
-
1.1 Ensure that every functionality available through the
user interface is also available through
every input API 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]
- 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 for checkpoint 1.1
- 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]
- 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 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 for checkpoint 1.2
- 1.3 Implement the standard keyboard API of the operating system
and ensure that every functionality available through the user interface is
available through this API. This checkpoint does not apply
when the operating system does not have a standard keyboard API.
[Priority 1]
- Note: This checkpoint is an important special case of checkpoint 1.1. Refer also to checkpoint
10.8.
- Techniques
for checkpoint 1.3
Checkpoints for user interface accessibility:
-
1.4 Ensure that the user can interact with all
active elements in a
device-independent manner.
[Priority 1]
- Note: For example, users who are blind or have physical
disabilities must be able to activate
text links, the links in a client-side image map, and form controls without a pointing device. This
checkpoint is an important special case of checkpoint 1.1.
-
Techniques for checkpoint 1.4
- 1.5 Ensure every non-text message (e.g.,
prompt, alert, notification, etc.) that is part of the user agent's user
interface also has a text
equivalent in the user interface. This text equivalent must be
available through an API.
[Priority 1]
- Note: For example, if the user is
notified of an event by an auditory cue, a text equivalent in the status bar
would satisfy this checkpoint. Using accessible standard interface controls
(per checkpoint 5.8) should
make text equivalents available to assistive technologies for rendering as
synthesized speech or Braille. Refer
also to checkpoint 5.5.
- Techniques for
checkpoint 1.5
Just as people use a variety of devices for
user interface input and output, they require that content be available in different modes --
auditory (synthesized and prerecorded), tactile (Braille), graphical, or a mix of some of these. Authors
and user agents share responsibility for ensuring redundant modes. Web content
providers specify equivalent alternatives for content, such as text equivalents for images or video, according
to the conventions of the markup language they are using (refer to the
Techniques document [UAAG10-TECHS] for details).
User agents must ensure that users have access to this content, as well as any
alternatives generated by the user agent itself. User agents should allow users
to specify whether primary content should be rendered, equivalent alternatives
should be rendered, or both.
Ensuring access to equivalent alternatives benefits all users since some
users may not have access to some content due to a technological limitation
(e.g., their mobile browser cannot display graphics) or simply a configuration
preference (e.g., they have a slow Internet connection and prefer not to
download images).
Checkpoints for content accessibility:
- 2.1 Make all
content available through the user interface. [Priority 1]
- Note: Users must have access to the
entire document
object through the user interface, including equivalent alternatives for content,
attributes, style sheets, etc. This checkpoint does not require that all
content be available in every viewport.
A document
source view is 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 for checkpoint 2.1
- 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]
- Techniques
for checkpoint 2.2
- 2.3 If
content available in a viewport has
equivalent alternatives, provide easy access to
the alternative equivalents through at least one of the following mechanisms:
(1) allowing configuration to render alternative instead of primary content;
(2) allowing configuration to render alternative in addition to primary
content; (3) allowing the user to select the primary content and then inspect
its alternatives; (4) providing a direct link to the alternative in content,
just before or after the primary content in document order. [Priority 1]
- Note: For example, if an image in an
HTML document has text
equivalents, provide access to them by rendering them nearby,
allowing the user to configure the user agent to render them in place of the
image, or allowing the user to follow a readily available link to them.
- Techniques
for checkpoint 2.3
-
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]
-
Techniques for checkpoint 2.4
- 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
including the non-text content.
[Priority 2]
- Note: 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 to repair the invalid content by generating a
text equivalent. Refer also to
checkpoint 2.6.
- Techniques for
checkpoint 2.5
- 2.6 When the author has specified an empty text equivalent for non-text content, do not generate one. [Priority 3]
- Note: Authors may provide an empty text equivalent (e.g.,
alt=""
) when one is required by specification, but the non-text
content has no other function than pure decoration. Please refer to the Web
Content Accessibility Guidelines 1.0 [WCAG10] for more details. Refer also to checkpoint 2.5.
- Techniques for
checkpoint 2.6
-
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]
- Note: For example, indicate that
content in a particular language has not been rendered with a text substitute
or with a graphical icon that has a text equivalent.
-
Techniques for checkpoint 2.7
Some content or behavior specified by the author may make the user agent
unusable or may obscure information. For instance, flashing content may trigger
seizures in people with photosensitive epilepsy, or may make a Web page too
distracting to be usable by someone with a cognitive disability. Blinking can
affect screen reader users, since screen readers (in conjunction with speech
synthesizers or Braille displays) may repeat the text every time it blinks.
Distracting background images, colors, or sounds make make it impossible for
users to see or hear other content.
Dynamically changing Web content may cause problems for some assistive
technologies. Scripts that cause unanticipated changes (viewports that open, automatically redirected
or refreshed pages, etc.) may disorient some users with cognitive
disabilities.
To ensure that users have access to content, user agents must allow them to
configure the user agent not to render certain content types when loading a
Web resource. A user agent must allow
this configurability even when it passes content (e.g., a sound file) to the
operating system or to a helper application for rendering; the user agent is
aware of the content type and thus can choose not to render it.
This guideline requires the user agent to allow configuration so that, when
loading a Web
resource, the user agent will not render portions of that resource
that are of a particular type, or the user agent will render those portions in
a way that will not pose accessibility problems. The checkpoints do not require
user agents to allow users to "turn on" pieces of content selectively that were
not rendered due to a global configuration setting. Thus, if the user has
configured the user agent not to render any video, there is no
requirement that the user agent allow the user to select and play an individual
video clip. Of course, user agents may provide such functionality.
Requirements for interactive control of rendered content are part of guideline 4.
Checkpoints for content accessibility:
-
3.1 Allow the user to configure
the user agent not to render background images.
[Priority 1]
- Note: Background images may make it difficult or
impossible to read superimposed text. When background images are not rendered,
user agents should render a solid background color. User agent may choose not
to retrieve the background image resource at all. Refer also to checkpoint 4.3 and
checkpoint
4.4.
- Note: This checkpoint only requires control of background
for "two-layered renderings", i.e., one rendered background (other than a solid
color) with all other content rendered "above it".
-
Techniques for checkpoint 3.1
- 3.2 Allow the user to configure the user agent not to render audio.
[Priority 1]
- Note: Audio may interfere with other sources of sound such
as the output of a speech synthesizer. User agents may play the audio
"silently". They may choose not to retrieve the resource at all. Refer also checkpoint 4.6, checkpoint 4.8 and checkpoint 4.9.
- Techniques
for checkpoint 3.2
- 3.3 Allow the user to configure the user agent not to render video.
[Priority 1]
- Note: The user agent should render a still image or an
icon to indicate that video has not been rendered. User agent may choose not to
retrieve the resource at all.
- Techniques for
checkpoint 3.3
- 3.4
Allow the user to configure
the user agent to render animated or blinking text as motionless text. [Priority 1]
-
Techniques for checkpoint 3.4
-
3.5 Allow the user to configure
the user agent to render animated or blinking images as motionless images.
[Priority 1]
- Note: Refer also to checkpoint 4.5 and checkpoint 4.6.
-
Techniques for checkpoint 3.5
- 3.6 Allow the user to configure the user agent not to execute scripts
and applets. [Priority 1]
- Note: This is particularly important for scripts that
cause the screen to flicker, since people with photosensitive epilepsy can have
seizures triggered by flickering or flashing, particularly in the 4 to 59
flashes per second (Hertz) range.
- Techniques
for checkpoint 3.6
-
3.7 Allow
configuration so that author-specified "client-side redirects"
(i.e., those initiated by the user agent, not the server) do not change content automatically. Allow the user to access
the new content manually (e.g., by following a link).
[Priority 2]
-
Techniques for checkpoint 3.7
-
3.8 Allow
configuration so that author-specified content refreshes do not
change
content automatically. Allow the user to
access the new content manually (e.g., by activating a button or following a
link). Advise the user to refresh content according to the same schedule as the
automatic refresh, and indicate when the user has not yet refreshed content.
[Priority 2]
-
Techniques for checkpoint 3.8
- 3.9 Allow the user to configure the user agent not to render images.
[Priority 2]
- Techniques for
checkpoint 3.9
Providing access to content (refer to guideline 2) includes enabling users to configure its rendering. Users with low vision
may require larger text than the default size specified by the author or the
user agent. Users with color blindness may need to impose or prevent certain
color combinations. Users with physical or cognitive disabilities may need to
configure the rate of a multimedia presentation.
For dynamic presentations such as synchronized multimedia presentations
created with SMIL 1.0
[SMIL], users with cognitive, hearing, visual, and physical
disabilities may not be able to interact with a presentation within the time
delays assumed by the author. To make the presentation accessible to these
users, user agents rendering synchronized multimedia presentations or
audio-only presentations must provide access to content in a
time-independent manner and/or allow users to adjust the playback rate of the
presentation.
User agents must also allow users to configure the style of the user
interface elements, such as styles for selection
and content
focus (e.g., to ensure adequate color contrast).
For more information about configuration, refer to guideline 10.
Note: The checkpoints in this guideline apply to all
content, including equivalent alternatives.
Checkpoints for fonts and colors:
- 4.1
Allow the user to configure and
control the reference size of text with an option to override
author-specified user agent default text size. Make available the range of
system font sizes. [Priority 1]
- Note: The reference size of 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 text size may vary among user agents. Control of text size may be
accomplished in different ways, for example by allowing the user to change the
font size or by allowing the user to zoom or magnify content.
-
Techniques for checkpoint 4.1
-
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]
- Note: For example, allow the user to
specify that all text must be rendered in a particular sans-serif font
family.
-
Techniques for checkpoint 4.2
-
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]
-
Techniques for checkpoint 4.3
-
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]
-
Techniques for checkpoint 4.4
Checkpoints for
multimedia presentations, audio-only presentations, and
visual-only presentations:
- 4.5 Allow the user to slow the
presentation rate of audio, video, and animations. For a visual track, provide
at least one setting between 40% and 60% of the original speed. For a
pre-recorded audio
track including audio-only presentations, provide at least one
setting between 75% - 80% of the original speed. For a synchronized multimedia
presentation where the visual track may be slowed from 100% to to 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]
- Refer also to
checkpoint 2.4.
- Techniques
for checkpoint 4.5
- 4.6 Allow the user to start, stop,
pause, resume, fast forward, and fast reverse audio, video, and animations.
[Priority 1]
-
Techniques for checkpoint 4.6
- 4.7 Allow the user to position text
transcripts,
collated text transcripts, and
captions on graphical
displays. The range of available positions must be the same range available to
the author according to specification.
[Priority 1]
-
Techniques for checkpoint 4.7
Checkpoints for audio volume control:
-
4.8 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]
- Note: User agents should allow global
control of volume through available system-level controls.
-
Techniques for checkpoint 4.8
-
4.9 Allow the user to control
independently the volumes of distinct audio sources synchronized to play
simultaneously. [Priority 1]
- Note: Refer also to checkpoint 4.11.
-
Techniques for checkpoint 4.9
Checkpoints for synthesized speech:
-
4.10 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]
-
Techniques for checkpoint 4.10
-
4.11 Allow the user to control the
synthesized speech volume independently of other sources of audio. [Priority 1]
- Note: Refer also to checkpoint 4.9.
-
Techniques for checkpoint 4.11
-
4.12 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]
- 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 for checkpoint 4.12
Checkpoints for user interface accessibility:
- 4.13
Allow the user to select from available
author and user style
sheets or to ignore them.
[Priority 1]
- Note: By definition, the user agent's default style sheet is always
present, but may be overridden by author or user styles.
-
Techniques for checkpoint 4.13
- 4.14 Allow the user to configure how the
selection is
highlighted (e.g., foreground and background color). 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]
-
Techniques for checkpoint 4.14
-
4.15 Allow the user to configure
how the content
focus is
highlighted (e.g., foreground and background color). Offer at least
three rendering options, including colors and fonts. 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]
-
Techniques for checkpoint 4.15
-
4.16 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]
-
Techniques for checkpoint 4.16
- 4.17 Allow the user to configure the user agent so that after one viewport is open, no other viewports open
except as the result of explicit user request.
[Priority 2]
- Note: Some users may become disoriented when there are too
many open viewports. In addition to configuration, user agents should allow the
user to
control the number of open viewports by
selecting and closing them. Following an author-specified link that opens a new
viewport does not constitute an explicit request from the user. Refer also to
checkpoint 4.16 and
checkpoint 5.5.
- Techniques
for checkpoint 4.17
Part of user agent accessibility involves communication within the user's
"accessibility environment." This includes:
- exchanging information about content and user agent user interface controls with other
user agents, especially with assistive
technologies.
- using standard communication channels for this exchange.
- ensuring the exchange takes place in a timely manner. Otherwise, assistive
technology rendering or response may lag behind that of the "source" user
agent, which can disorient the user. Timely exchange is also necessary for
proper synchronization of alternative renderings and simulation of events.
- following system conventions for user
agent user interface design,
documentation, and installation.
- incorporating system-level user preferences into the user agent. For
instance, some operating systems include settings that allow users to request
high-contrast colors (for users with low vision) or graphical rendering of
audio cues (for users with hearing disabilities).
Using interoperable APIs and following system conventions increases
predictability for users and for developers of assistive
technologies.
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 modules and exporting the interfaces they define. [Priority 1]
- Note: These modules are defined in DOM
Level 2
[DOM2], chapters 1 and 2. Please refer to that specification for
information about which versions of HTML and
XML are supported and for the definition of a "read-only"
DOM. This checkpoint is an important special case of checkpoint 2.1. For content
other than HTML and XML, refer to checkpoint 5.3.
- Techniques
for checkpoint 5.1
- 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 modules and exporting the interfaces they define. [Priority 1]
- Note: For example, if the user
interface allows users to complete HTML forms, this must
also be possible through the DOM
APIs. These modules are defined in DOM
Level 2
[DOM2], chapters 1 and 2. Please refer to DOM
Level 2
[DOM2] for information about which versions of
HTML and XML are supported. This checkpoint is an
important special case of
checkpoint 2.1. For markup languages other than HTML and XML, refer to checkpoint 5.3.
- Techniques
for checkpoint 5.2
- 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]
- Note: This checkpoint addresses content
not covered by checkpoints
checkpoint 5.1 and
checkpoint 5.2. This checkpoint is an important special case of checkpoint 2.1.
-
Techniques for checkpoint 5.3
- 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 for the operating system,
and conventions for programming languages, plug-ins, virtual machine
environments, etc.) [Priority 1]
- 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 for
checkpoint 5.4
- 5.5 Using standard
APIs, provide programmatic notification
of changes to content and
user
interface controls (including
selection, content
focus, and user
interface focus).
[Priority 1]
- Note: Use the standard APIs required by guideline 5.
- Techniques for
checkpoint 5.5
- 5.6 Ensure that programmatic exchanges
proceed in a timely manner.
[Priority 2]
- 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
for checkpoint 5.6
- 5.7 For user agents that support
Cascading Style Sheets ([CSS1], [CSS2]), provide programmatic access
to CSS style sheets by conforming to the W3C Document Object
Model (DOM) Level 2
CSS module and exporting the interfaces it defines. [Priority 3]
- Note: This module is defined in DOM
Level 2
[DOM2], chapter 5. Please refer to that specification for
information about which versions of CSS are supported. This
checkpoint is an important special case of checkpoint 2.1.
- Techniques
for checkpoint 5.7
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]
- 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 10.2.
- Techniques
for checkpoint 5.8
Developers should implement open and accessible specifications. Conformance
to open specifications promotes interoperability and accessibility by making it
easier to design assistive
technologies (also discussed in guideline 5).
While developers should implement the accessibility features of any
specification, this document promotes W3C specifications for several
reasons:
- W3C specifications include "built-in" accessibility features.
- W3C specifications undergo early review to ensure that accessibility issues
are considered during the design phase. W3C encourages the public to review and
comment on specifications at all times during their development, from Working
Draft to Candidate Recommendation (for implementation experience) to Proposed
Recommendation.
- W3C specifications are developed in a consensus process that includes
stakeholders in accessibility. Refer to the process defined by the W3C Process
Document
[W3CPROCESS]. For information about how specifications become W3C
Recommendations, refer to The
W3C Recommendation track ([W3CPROCESS], section 6.2). W3C
Recommendations (and other technical
reports) are published at the W3C Web site.
Checkpoints for content accessibility:
-
6.1 Implement the accessibility features of all supported
specifications (markup languages, style sheet languages, metadata languages,
graphics formats, etc.). Accessibility features are those identified in the
specification and those features of the specification that support requirements
of the "Web Content Accessibility Guidelines 1.0" [WCAG10], the "Authoring Tool
Accessibility Guidelines 1.0" [ATAG10], and the current document.
[Priority 1]
- Note: This checkpoint applies to all specifications, not
just W3C specifications. The Techniques document
[UAAG10-TECHS] provides information about the accessibility features
of some specifications, including W3C specifications.
-
Techniques for checkpoint 6.1
- 6.2 Use and conform to W3C
Recommendations when they are available and appropriate for a task. [Priority 2]
- Note: For instance, for markup,
implement HTML 4.01 [HTML4], XHTML 1.0 [XHTML10], or
XML 1.0 [XML]. For style sheets, implement
CSS ([CSS1], [CSS2]). For mathematics, implement
MathML
[MATHML]. For synchronized multimedia, implement
SMIL 1.0
[SMIL]. For information about programmatic access to
HTML and XML content, refer to guideline 5.
- Note: For reasons of backward
compatibility, user agents should continue to implement deprecated features of
specifications. The current guidelines refer to some deprecated language
features that do not necessarily promote accessibility but are widely deployed.
Information about deprecated language features is generally part of the
language's specification.
-
Techniques for checkpoint 6.2
Users should be able to navigate to important pieces of content within a
configurable view, identify the type of object they have navigated to, interact
with that object easily (if it is an
active element), and recall the surrounding context (to orient
themselves). Providing a variety of navigation mechanisms helps users with
disabilities (and all users) access content more quickly. Content navigation is
particularly important to users who access content serially (e.g., as
synthesized speech or Braille).
Sequential navigation (e.g., line scrolling, page scrolling, sequential
navigation through active elements, etc.) means advancing (or rewinding)
through rendered content in well-defined steps (line by line, screen by screen,
link by link, etc.). Sequential navigation can provide context, but can be
time-consuming. Sequential navigation is important to users who cannot scan a
page visually for context and benefits all users unfamiliar with a page.
Sequential access may be based on element type (e.g., links only), content
structure (e.g., navigation from heading to heading), or other criteria.
Direct navigation (go to a particular link or paragraph, search for
instances of a string, etc.) is faster than sequential navigation, but
generally requires familiarity with the content. Direct navigation is important
to users with some physical disabilities (who may have little or no manual
dexterity and/or increased tendency to push unwanted buttons or keys) and
benefits all "power users." Selecting text or structured content with the
pointing device is another form of direct navigation. Searching on text is one
important variant of direct navigation.
Structured navigation mechanisms offer both context and speed. User agents
should allow users to navigate to content known to be structurally important:
blocks of content, headers and sections, tables, forms and form elements,
active elements, navigation mechanisms, containers, etc. For information about
programmatic access to document structure, refer to guideline 5.
User agents should allow users to configure navigation mechanisms (e.g., to
allow navigation of links only, or links and headings, or tables and forms,
etc.). For more information about configuration, refer to guideline 10.
Checkpoints for user interface accessibility:
- 7.1 Allow the user to navigate among all
viewports (including frames). [Priority 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 for
checkpoint 7.1
-
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]
- Note: For example, when the user
navigates from one viewport to another (per checkpoint 7.1) and back, the point of regard should be restored.
-
Techniques for checkpoint 7.2
- 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]
- Note: Navigation may include non-active
elements in addition to active elements. This checkpoint is an important
special case of checkpoint
7.6.
- Techniques for
checkpoint 7.3
- 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]
- Techniques
for checkpoint 7.4
- 7.5 Allow the user to search for rendered text
content, including rendered text
equivalents. Allow the user to start a forward search from a
location in content selected or focused by the user. After a match, allow
searching from location of the match. Provide a case-insensitive search option
when applicable to the natural
language of text.
[Priority 2]
- Note: The default search starting point should be the
beginning of content. Use operating system conventions for marking the result
of a search (e.g., selection
or content
focus).
- Techniques for
checkpoint 7.5
- 7.6 Allow the user to navigate efficiently
to and among important structural elements identified by the author. For markup
languages with known semantics, allow forward sequential navigation to
important structural elements. For other markup languages, allow at least
forward sequential navigation of the document object, in document order. In
HTML 4
[HTML4], the list of important elements is:
A
,
ADDRESS
, BUTTON
, FIELDSET
, DD
,
DIV
, DL
, DT
, FORM
,
FRAME
, H1-H6
, IMAGE
, INPUT
,
LI
, MAP
, OBJECT
, OL
,
OPTGROUP
, OPTION
, P
, TABLE
,
TEXTAREA
, and UL
. In SMIL 1.0 [SMIL], the list of
important elements is: a
, anchor
, par
,
seq
, and switch
. In SVG 1.0 [SVG], the important elements are
a
and g
.
[Priority 2]
- Note: Structured navigation of
headings, tables, forms, lists, etc., is most effective when available in
conjunction with a configurable view (checkpoint 8.4 and checkpoint 8.5). User agents should follow operating system
conventions for indicating navigation progress (e.g.,
selection or content
focus).
- Techniques for
checkpoint 7.6
- 7.7
Allow the user to configure and
control the set of elements navigable according to checkpoint 7.6 by allowing
inclusion and exclusion of element types in the navigation sequence. [Priority 3]
- Note: For example, allow the user to navigate only
paragraphs, or only headings and paragraphs, etc.
-
Techniques for checkpoint 7.7
All users require clues to help them understand their "location" when
browsing. Some mechanisms that provide such clues include:
- Highlighted (either graphically or aurally)
selection and content
focus mechanisms, which distinguish the selected or focused content
from other content.
- A history mechanism, which allows users to return to a familiar or
comprehensible "state".
Orientation mechanisms such as these are especially important to users who
view content serially, (e.g., when rendered as speech or Braille). For
instance, these users cannot "scan" a graphically displayed table with their
eyes for information about a table cell's headers, neighboring cells, etc. User
agents must provide other means for users to understand table cell
relationships, frame relationships (what relationship does the graphical layout
convey?), form context (have I filled out the form completely?), link
information (have I already visited this link?), etc.
User agents must make orientation information available in an output device
independent manner. Refer also
to guideline 1.
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]
- Note: Depending on the table, some techniques may be more
efficient than others for conveying data relationships. For many tables,
graphical user agents may satisfy this checkpoint by rendering a table as a two
dimensional 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 for
checkpoint 8.1
- 8.2 Render recently visited links in a
distinct style. Allow the user to configure this style and 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]
- 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
8.6.
- Techniques
for checkpoint 8.2
- 8.3 Render in a distinct style those links
that have been marked up to indicate that following them will involve a fee.
Allow the user to configure this style and 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]
- Note: This checkpoint is an important
special case of checkpoint
8.6.
- Techniques for
checkpoint 8.3
- 8.4
Make available to the user an "outline" view of
content, composed of text labels for important structural elements
(e.g., heading text, table titles, form titles, etc.). The set of important
structural elements is the same required by checkpoint 7.6.
[Priority 2]
- 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 use generate a brief text label (e.g., from content, the element type,
etc.).
-
Techniques for checkpoint 8.4
-
8.5 Allow the user to configure and
control the outline view of checkpoint 8.4 to include and exclude element types. [Priority 3]
- Note: For example, allow the user to configure the level of detail of the outline.
Refer also to checkpoint
8.4 and checkpoint
5.4.
-
Techniques for checkpoint 8.5
- 8.6 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]
- Techniques for
checkpoint 8.6
Checkpoints for user interface accessibility:
-
8.7 Implement
selection, content
focus, and user
interface focus mechanisms. Implement them according to system
conventions per checkpoint
5.8. [Priority 1]
- Note: This checkpoints refers to the semantics of
the selection and focus; requirements for rendering are addressed by checkpoint 8.8,
checkpoint 4.15,
and checkpoint
4.14. Refer also to checkpoint
7.1.
-
Techniques for checkpoint 8.7
- 8.8 Provide a mechanism
for
highlighting and identifying (through a
standard interface where available) the current
viewport,
selection, and content
focus. [Priority 1]
- Note: This includes highlighting and
identifying frames. This checkpoint is an important special case of checkpoint 1.1. Refer also to checkpoint 8.6.
-
Techniques for checkpoint 8.8
- 8.9 Provide a mechanism for highlighting and identifying
active elements.
[Priority 2]
- Note: On most systems, the focus is used to identify and highlight active
elements.
- Techniques
for checkpoint 8.9
For people with visual disabilities or certain types of learning
disabilities, it is important that the point of regard remain as stable as possible.
Unexpected changes may cause users to lose track of how many viewports are open, which is the current
viewport, etc. User agents should notify the user of content and viewport
changes caused by scripts, or allow users to turn off scripts entirely (refer
to checkpoint 3.6).
Refer to checkpoint 5.5 for
requirements about notification of user interface changes through an API.
Checkpoints for user interface accessibility:
-
9.1 Ensure that when the selection
or content
focus changes, it is in a viewport
after the change. [Priority 2]
- Note: For example, if users navigating
links move to a portion of the document outside the viewport, the viewport
should scroll to include the new location of the focus.
-
Techniques for checkpoint 9.1
- 9.2 Allow configuration so the user is
prompted to confirm any form submission not caused by explicit activation of a
form submit control. [Priority 2]
- 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
for checkpoint 9.2
- 9.3 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]
- 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
for checkpoint 9.3
Web users have a wide range of capabilities and must be able to configure the user agent according to their
preferences for styles, graphical user interface configuration, keyboard
configuration, etc.
Checkpoints for user interface accessibility:
-
10.1 Provide information to the user about current user preferences
for input
configurations (e.g., keyboard or voice bindings). [Priority 1]
-
Techniques for checkpoint 10.1
-
10.2 Avoid default input
configurations that interfere with operating system accessibility
conventions. [Priority 1]
- 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 for checkpoint 10.2
-
10.3 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]
-
Techniques for checkpoint 10.3
- 10.4 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 10.8). 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]
- Note: This checkpoint applies to all
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
10.5, checkpoint
10.9, checkpoint
10.8, and checkpoint
11.3.
- Techniques
for checkpoint 10.4
- 10.5 Allow the user to override the
default keyboard
configuration as follows: Allow the user to override any binding
that is part of the user agent default keyboard configuration (checkpoint 10.8). The user
agent is not required to allow the user to override standard keyboard bindings
for the operating system (e.g., for access to help). Allow the user to assign a
single key binding to at least a majority of the functionalities available in
the default keyboard configuration.
[Priority 2]
- Note: This checkpoint applies to the
keyboard only and always applies on systems with a standard keyboard API. 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 10.4. Refer also to checkpoint 1.3, checkpoint 10.9, checkpoint 10.8, and checkpoint 11.3.
- Techniques
for checkpoint 10.5
-
10.6 Follow operating system conventions to indicate the input
configuration. [Priority 2]
- 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 for checkpoint 10.6
- 10.7 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]
- 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
notification.
- Techniques for
checkpoint 10.7
- 10.8
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 implements 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]
-
Techniques for checkpoint 10.8
- 10.9 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]
- Note: This checkpoint is an important special case of checkpoint 10.4.
-
Techniques for checkpoint 10.9
Documentation includes anything that explains how to install, get
help for, use, or configure the product. At least one version of the
documentation must conform to the Web Content Accessibility Guidelines 1.0
[WCAG10].
Features that support accessibility must be clearly documented so that users
with disabilities can learn to operate the user agent efficiently.
Documentation of keyboard accessibility is particularly important to users with
visual disabilities and some types of physical disabilities. Without this
documentation, a user with a disability (or multiple disabilities) may not
think that a particular task can be performed. Or the user may try to use a
much less efficient technique to perform a task, such as using a mouse, or
using an assistive technology's mouse emulation key strokes.
Refer also to checkpoint
5.8.
Checkpoints for accessible documentation:
- 11.1 Provide a version of the product
documentation that conforms to at least
Level Double-A of the Web Content Accessibility Guidelines 1.0 [WCAG10]. [Priority 1]
- Note: User agents may provide
documentation in many formats, but at least one must conform to at least Level
Double-A of the Web Content Accessibility Guidelines 1.0 [WCAG10].
- Techniques
for checkpoint 11.1
-
11.2
Document all user agent features that promote accessibility. [Priority 1]
- Note: For example, review the
documentation or help system to ensure that it includes information about the
accessibility requirements of
WAI Guidelines.
-
Techniques for checkpoint 11.2
-
11.3
Document the default input configuration (e.g., default keyboard
bindings). [Priority 1]
-
Techniques for checkpoint 11.3
-
11.4 In a dedicated section of the
documentation, describe all features of the user agent that promote
accessibility. [Priority 2]
- Note: This is a more specific
requirement than
checkpoint 11.2.
-
Techniques for checkpoint 11.4
- 11.5 In each software release,
document all changes that affect
accessibility. [Priority 2]
- Note: Features that affect accessibility are listed in
this document and in platform-specific accessibility guidelines.
- Techniques
for checkpoint 11.5
This normative section explains how to make a
valid claim that a user agent conforms to this document. The terms "must",
"should", and "may" (and related terms) are used in this document in accordance
with RFC 2119
[RFC2119].
Anyone may make a claim (e.g., vendors about their own products, third
parties about those products, journalists about products, etc.). Claims may be
published anywhere (e.g., on the Web or in product documentation).
Claimants are solely responsible for their claims and the use of the conformance icons. If the subject of the claim -- the set of components for
which conformance is being claimed -- change after the date of the claim, the
claimant is responsible for updating the claim. Claimants are encouraged to
conform to the most recent guidelines available.
Users with disabilities often require more than one user agent for full
access to the Web. For example, a user might require a graphical desktop
browser, a multimedia player, and specialized assistive
technologies such as screen readers, which are useful for
controlling speech output and refreshable braille display. This document
focuses on the accessibility of mainstream user agents so that most users with
disabilities will have access to the Web when using a conforming user agent in
conjunction with assistive technologies. There are also requirements in this
document to make user agents more accessible to those users with disabilities
who do not require assistive technologies for full access.
Developers of mainstream graphical user agents are strongly
encouraged to design user agents that conform in their default configuration.
Users may not be able to install complementary software because the default
configuration does not allow it easily (e.g., the mechanisms for retrieving and
installing plug-ins are not accessible by default), because they don't have
access privileges on a public computer, etc. In order for people to use the
user agent at all, the installation procedure (and any subsequent software
update procedures) must be accessible according to the guidelines of this
document. For example, the user agent must provide device-independent access
and accessible documentation of the installation.
User agent developers are encouraged to adopt operating system features to
meet the requirements of this document. However, if these features are not
accessible, the user agent must provide an alternative accessible solution.
User agent developers may, but are not required to, provide access to adopted
operating system features through the user agent's user interface. For example,
if the user agent relies on the operating system's audio control features to
meet some requirements of this document, the user agent is not required to
include those controls in its own user interface.
Note: Some user agents may not conform to this document but
still be accessible to some users with disabilities.
This document has not been designed so that assistive technologies and other
specialized user agents conform when used independently. Nonetheless, this
document should benefit assistive technology developers because it explains
what information an assistive technology should expect from a conforming user
agent. Also, many of the design principles in this document apply to all
software.
Each checkpoint requirement must be satisfied by making information or
functionalities available through the user agent's
user interface unless the checkpoint
explicitly states that the requirement must be met by making information
available through an Application Programming Interface (API); these checkpoints are labeled
"checkpoints for communication with other software."
At each conformance level, the user agent
must satisfy each checkpoint required for that level
unless:
- The checkpoint refers to a content type (or "media type" as defined in RFC
2046
[RFC2046]) that the user agent does not support.
- The checkpoint refers to a role of content (e.g., transcript, caption, text
equivalent, etc.) that the user agent does not
recognize. For instance, HTML user agents can recognize "alt",
OBJECT content, or NOFRAMES content as providing equivalents for other content
since these are specified by the markup language. HTML user agents are not
expected to recognize that an image description embedded in a paragraph is a
text equivalent for the image.
- The checkpoint requires control of properties of content (e.g., video or
animation rate) that the user agent cannot control (e.g., the format does not
allow it) or does not recognize
(e.g., because the property is controlled by a script in a manner that the user
agent cannot recognize).
- The checkpoint refers to an output mode (visual, speech, tactile) that the
user agent does not support. If a user agent supports an output mode the user
agent must be accessible through that output mode.
Some checkpoints include more than one requirement. User agents are required
to satisfy all applicable requirements of a checkpoint.
A conformance claim must indicate what conformance level is met:
Note: Conformance levels are spelled out in text (e.g.,
"Double-A" rather than "AA") so they may be understood when rendered as
speech.
A well-formed claim must include the following information:
- About the guidelines:
-
- The guidelines title/version: "User Agent Accessibility Guidelines
1.0".
- The URI of the guidelines:
http://www.w3.org/WAI/UA/WD-UAAG10-20000901.
- The conformance level satisfied: "A",
"Double-A", or "Triple-A".
- The checkpoints of the chosen conformance level considered not applicable. Claimants may use the checklist
[UAAG10-CHECKLIST] for this purpose.
- The subject of the claim may consist of one or more software components.
For each component, the claim must include the following:
-
- The product name and version information (version number, minor release
number, and relevant bugfix update level). The claim must also include the
vendor name if it is required to identify the product.
- The operating system name and version number.
- Properties of the claim:
-
There is no restriction on the format used to make the claim, except that at
least one representation of the claim must be accessible according to the Web
Content Accessibility Guidelines 1.0 [WCAG10]. For instance, the claim
may be marked up using HTML, or expressed in the Resource Description Framework
(RDF) [RDF10] Here is an example of a
claim expressed in HTML:
<p>On 1 September 2000, this product (version 2.3 on
MyOperatingSystem) conforms to <abbr title="the World Wide Web
Consortium">W3C</abbr>'s "User Agent Accessibility Guidelines 1.0",
http://www.w3.org/WAI/UA/WD-UAAG10-20000901, level Double-A. The <a
href="http://example.com/checkpoints"> list of checkpoints that do not
apply</a> is available online.</p>
A conformance claim is valid for a given
conformance level if:
- The claim is well-formed, and
- The subject of the claim satisfies all the applicable
checkpoints for that level.
Claimants (or relevant assuring parties) are responsible for the validity of
a claim. As of the publication of this document, W3C does not act as an
assuring party, but it may do so in the future, or establish recommendations
for assuring parties.
Claimants are expected to modify or retract a claim if it may be
demonstrated that the claim is not valid. Please note that it is not currently
possible to validate claims completely automatically.
As part of a conformance claim, people may use a conformance icon on a Web
site, on product packaging, in documentation, etc. Each conformance icon
(chosen according to the appropriate conformance
level) must link to the W3C explanation of the icon. The appearance of a
conformance icon does not imply that W3C has reviewed or validated the claim.
An icon must be accompanied by a well-formed
claim.
Note: In the event this document becomes a W3C
Recommendation, additional information about the icons and how to use them will
be available at the W3C Web site.
-
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 4.01
[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 field). Refer also to
the definition of event
handler.
- Application
Programming Interface (API)
- An application programming interface (API) defines how
communication may take place between applications.
- Assistive technology
- In the context of this document, an assistive technology
is a
user agent that:
- 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.
- 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:
- screen magnifiers, which are used by people with visual disabilities to
enlarge and change colors on the screen to improve the visual readability of
text and images.
- screen readers, which are used by people who are blind or have reading
disabilities to read textual information through synthesized speech or Braille
displays.
- speech recognition software, which may be used by people who have some
physical disabilities.
- alternative keyboards, which are used by people with certain physical
disabilities to simulate the keyboard.
- alternative pointing devices, which are used by people with certain
physical disabilities to simulate mouse pointing and button activations.
- 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). 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 content 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 two
ways:
- Content refers to the document
object as a whole or in parts. Phrases such as "content type", "text
content", and "language of content" refer to this usage. When used in this
sense, the term content encompasses equivalent alternatives. Refer also to the
definition of rendered
content. and other accessibility information.
- 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.
-
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
- The document object is 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.) or produced as a result of
preferences set within the user agent. 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
invisibly by the user agent, 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 will vary in implementation and sometimes in scope.
Nevertheless, this document calls for developers of user agents to adhere to
the W3C Document Object Model
(DOM), which specifies a standard interface
for accessing HTML and XML content. This standard interface allows authors to
access and modify the document with a scripting language (e.g., JavaScript) in
a consistent manner across different scripting languages. As a standard
interface, use of a W3C DOM makes 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. In this
specification, the acronym "DOM" refers to the W3C DOM.
-
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. A document source view
represents all or part of a document in a way that exposes the markup
language(s) used to build the Web resource. A source view often presents
textual representations of content. Refer also to the definition of 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
alternatives for content
- Since content in
some forms is not always accessible to users with disabilities, authors must
provide equivalent alternatives for inaccessible content. In the context of
this document, the equivalent must fulfill essentially the same function for
the person with a disability (at least insofar as is feasible, given the nature
of the disability and the state of technology), as the "primary" content does
for the 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. Note that equivalent information focuses on fulfilling the same
function. If the image is part of a link and understanding the image is crucial
to guessing the link target, an equivalent must also give users an idea of the
link target.
- Equivalent alternatives of content include text equivalents
(long and short, synchronized and unsynchronized) and non-text equivalents
(e.g., an auditory
description, or a visual track that shows a sign language
translation of a written text, etc.). Please also consult the Web Content
Accessibility Guidelines 1.0 [WCAG10] and its associated
Techniques document [WCAG10-TECHS].
- Each markup language defines its own mechanisms for
specifying equivalent alternatives. For instance, in HTML 4.01 [HTML4] or SMIL
1.0 [SMIL],
the "alt" attribute specifies alternative text for many elements. In HTML 4.01,
authors may provide alternatives 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 alternatives, and NOSCRIPT for script
alternatives), and in prose.
- Events and
scripting, event handler
- User agents often perform a task when a certain event
occurs, caused by user interaction (e.g., 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
a specific event occurs, such as document loading and unloading, mouse press or
hover events, keyboard events, and other user interface events.
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.
-
Focus,
content focus,
user interface focus, current focus
- The notion of focus refers to two identifying mechanisms
of user agents:
- The "content focus" designates an
active element in a document. A viewport has at most one content
focus.
- 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.).
The term "focus" 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, graphics, colors, etc.) rendered for visual consumption.
-
Highlight
- A highlight mechanism emphasizes selected or focused
content. For example, 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 included in the user agent
documentation.
-
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 4.01 ([HTML4] section
8.1), the
"xml:lang" attribute in XML 1.0 ([XML], section 2.12),
the
HTML 4.01 "hreflang" attribute for links in HTML 4.01
([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 of a
viewport is its position in rendered content. What is meant precisely by
"the point of regard" may vary since users may be viewing rendered content with
browsers that render in various ways (graphically, as speech, as Braille, etc.).
Depending on the user agent and browsing context, it may refer to a two
dimensional area (e.g., for graphical rendering) or a single point (e.g., for
aural rendering or voice browsing). 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.
- 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 semantics 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
text and title of a link 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, audio, or tactile).
- 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.
- Standard device
APIs
- Operating systems are designed to be used by default with
devices such as pointing devices, keyboards, voice input, etc. The operating
system (or windowing system) provides "standard
APIs" for these devices. 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.
- Synchronize
- In this document, the term synchronize has two meanings:
- 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.
- The coordination of user interface changes (e.g., focus changes) among two
or more
viewports.
-
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
- A user agent is software that retrieves and renders Web
content, including text, graphics, sounds, video, images, and other content
types. A user agent may require additional user agents that handle some types
of content. For instance, a browser may run a separate program or plug-in to
render sound or video. User agents include graphical desktop browsers,
multimedia players, text browsers, voice browsers, and assistive
technologies such as screen readers, screen magnifiers, speech
synthesizers, onscreen keyboards, and voice input software.
-
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:
- 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.
- 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.
-
User-initiated, user agent initiated
- An action initiated by the user is one that results from
user operation of the user interface. An action initiated by the user agent is
one that results from the execution of a script (e.g., an
event handler bound to an event not
triggered through the user interface), from operating system conditions, or
from built-in user agent behavior.
-
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 should
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 has identity on the Web. A Web resource is identified by a
URI.
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.
- [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.
- [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.
- [DOM2]
- "Document
Object Model (DOM) Level 2 Specification", L. Wood, A. Le Hors, V.
Apparao, L. Cable, M. Champion, J. Kesselman, P. Le Hégaret, T. Pixley,
J. Robie, P. Sharpe, C. Wilson, eds., 10 May 2000. This W3C Candidate
Recommendation is http://www.w3.org/TR/2000/CR-DOM-Level-2-20000510.
- [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.
- [RDF10]
- "Resource
Description Framework (RDF) Model and Syntax Specification", O.
Lassila, R. Swick, eds., 22 February 1999. This W3C Recommendation is
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222.
- [RFC2046]
- "Multipurpose Internet
Mail Extensions (MIME) Part Two: Media Types", N. Freed and N.
Borenstein, November 1996.
- [RFC2119]
- "Key words for use in
RFCs to Indicate Requirement Levels", S. Bradner, March 1997.
- [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.
- [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/.
-
[UAAG10-CHECKLIST]
- An appendix to this document lists all of the checkpoints, sorted by
priority. The checklist is available in either tabular
form or list
form.
-
[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/WAI/UA/UAAG10-TECHS/.
- [W3CPROCESS]
-
World Wide Web Consortium Process Document, I. Jacobs ed. The 11
November 1999 version of the Process Document is
http://www.w3.org/Consortium/Process/Process-19991111/.
- [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.
- [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.
- [XML]
- "Extensible
Markup Language (XML) 1.0", T. Bray, J. Paoli, C.M.
Sperberg-McQueen, eds., 10 February 1998. This XML 1.0 Recommendation is
http://www.w3.org/TR/1998/REC-xml-19980210.
The active participants of the User Agent Accessibility Guidelines Working
Group who authored this document were: James Allan, Denis Anson, Kitch
Barnicle, Harvey Bingham, Dick Brown, Al Gilman, Jon Gunderson, Eric Hansen,
Ian Jacobs, Marja-Riitta Koivunen, Tim Lacy, Charles McCathieNevile, Mark
Novak, David Poehlman, Mickey Quenzer, Gregory Rosmaita, 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.