User Agent Accessibility Guidelines 1.0
W3C Working Draft 13 January 2001
- This version:
-
http://www.w3.org/WAI/UA/WD-UAAG10-20010113
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- Latest version:
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http://www.w3.org/WAI/UA/UAAG10
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http://www.w3.org/WAI/UA/WD-UAAG10-20001229
- Editors:
- Ian Jacobs, W3C
Jon Gunderson, University of Illinois at
Urbana-Champaign
Eric Hansen, Educational Testing
Service
- Authors and Contributors:
- See acknowledgements.
Copyright
©1999 - 2001 W3C® (MIT,
INRIA, Keio), All Rights
Reserved. W3C
liability,
trademark, document
use and software
licensing rules apply.
This document provides guidelines for designing user
agents that lower barriers to Web accessibility for people with
disabilities (visual, hearing, physical, and cognitive). User agents include
HTML browsers and other types of software that retrieve and render Web content. A user agent that conforms to these guidelines will promote accessibility
through its own user interface and through other internal facilities, including
its ability to communicate with other technologies (especially assistive
technologies). By following these guidelines, developers will create
more usable software for all Web users.
In addition to helping developers of HTML browsers, media players, etc.,
this document will also benefit developers of assistive technologies because it
explains what types of information and control an assistive technology may
expect from a conforming user agent. Technologies not addressed directly by
this document (e.g., technologies for braille rendering) will be essential to
ensuring Web access for some users with disabilities.
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 version of the document incorporates UAWG
resolutions to some issues raised during the second last call. This document
includes some changes not yet agreed on by the Working Group, and does not yet
address all issues raised during last call.
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."
This document is part of a series of accessibility documents published by
the Web Accessibility Initiative (WAI) of the World Wide Web
Consortium (W3C). WAI
Accessibility Guidelines are produced as part of the WAI Technical Activity. The
goals of the User Agent Accessibility
Guidelines Working Group are described in the charter.
A list of current W3C Recommendations and
other technical documents can be found at the W3C Web site.
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. The techniques provided in "Techniques
for User Agent Accessibility Guidelines 1.0" are informative examples only, and
other strategies may be used or required to satisfy the checkpoints. The
Techniques document is expected to be updated more frequently than the current
guidelines.
The Web Accessibility Initiative provides other resources and educational materials
to promote Web accessibility. Resources include information about accessibility
policies, links to translations of WAI materials into languages other than
English, information about specialized user agents and other tools,
accessibility training resources, and more.
This document specifies requirements that user
agent developers must satisfy to lower barriers to accessibility.
This introduction (section 1) provides context for understanding the guidelines
listed in section 2. Section 1 explains the
relationship of this document to other accessibility guidelines published by
the Web Accessibility Initiative, which user agents are expected to conform, known limitations of this document, and the
relationship of this document to other software design guidelines. Section 3
explains how to make claims that software conforms
to these guidelines and details about the applicability of the requirements for
different kinds of user agents.
"User Agent Accessibility Guidelines 1.0" (UAAG 1.0) is
part of a series of accessibility guidelines published by the Web Accessibility Initiative (WAI). The documents in this
series reflect an accessibility model in which Web content authors, format
designers, and software developers have roles in ensuring that users with
disabilities have access to the Web. These roles intersect as follows:
- Protocol (e.g., HTTP) and content format (e.g., HTML, XML, SVG, etc.)
specifications allow communication on the Web. These specifications includes
features that authors may use to create accessible content, and features that
user agents must support through an accessible user interface. For instance,
authors must provide accessible alternatives to inaccessible content, and user
agents must allow users to access these alternatives.
- Authors make use of the accessibility features of different format
specifications, they use markup appropriately, they write in clear and simple
language, organize a Web site consistently, etc. The "Web Content Accessibility
Guidelines 1.0"
[WCAG10] explains the responsibilities of authors in meeting the
needs of users with disabilities. In User Agent Accessibility Guidelines 1.0,
WCAG 1.0 is considered the reference for what defines accessible Web content.
The "Authoring Tool Accessibility Guidelines 1.0" [ATAG10] explains the
responsibilities of authoring tool developers. An accessible authoring tool
facilitates the creation of accessible Web content and may be operated by users
with disabilities.
- User agent developers design software that conforms to specifications
(including implementation of their accessibility features), provides an
accessible user interface, accessible documentation, and communicates with
other software (notably assistive
technologies).
This document explains the responsibilities of user agents in meeting the
needs of users with disabilities. The requirements of this document interact
with those of the "Web Content Accessibility Guidelines 1.0" [WCAG10] in a
number of ways:
- UAAG 1.0
checkpoint 6.1 requires implementation of the accessibility features of all
implemented specifications. Features are those identified as such and those
that satisfy all of the requirements of WCAG 1.0 [WCAG10].
- UAAG 1.0 checkpoint 10.1
requires conformance to WCAG 1.0 for user agent documentation.
- UAAG 1.0 also incorporates some terms and concepts from WCAG 1.0, a natural
consequence of fact that the documents were designed to complement one
another.
Formats, authors, and designers all have limitations. No format allows
authors to encode all of their knowledge in a way that a user agent can recognize. A format may lack features required
for accessibility. An author may not make use of the accessibility features of
a format or may misuse a format (which can cause problems for user agents). A
user agent designer may not implement a format specification correctly or
completely. Some requirements of this document take these limitations into
account.
- UAAG 1.0 includes requirements to satisfy the expectations set by WCAG 1.0
"until user agent" clauses. These clauses make additional requirements of
authors in order to compensate for some limitations of deployed user
agents.
- UAAG 1.0 includes several
repair requirements (e.g., checkpoints checkpoint 2.6 and checkpoint 2.8) for cases where content does not conform to
WCAG 1.0. Some requirements in this document support authoring practices that
may be widely deployed but that are discouraged because they cause
accessibility or usability problems (e.g., some uses of HTML frames).
- Except for the indicated repair checkpoints, UAAG 1.0 only requires user
agents to handle what may be
recognized through protocols and formats. For example, user agents
are not expected to recognize that the author has used "clear and simple"
language to express ideas. Please see the section on
checkpoint applicability for more information about what the user agent is
expected to recognize.
This document was designed specifically to improve the accessibility of
mainstream user agents with multimedia capabilities for users with one or more
disabilities (visual, hearing, physical, and cognitive). In this context, a
mainstream user agent is one designed for the general public to handle
general-purpose content in ordinary operating conditions. It is expected that a
conforming user agent will typically consist of a
Web browser, one or more media players, and possibly other components.
A user agent that conforms to these guidelines will enable access through
its own user interface and through other internal facilities, including its
ability to communicate with other technologies (especially assistive
technologies). Technologies not addressed directly by this document
(e.g., those for braille rendering) will be essential to ensuring Web access
for some users with disabilities. Note that the ability of conforming user
agents to communicate well with assistive technologies will depend in part on
the willingness of assistive technology developers to follow the same standards
and conventions for communication.
This document allows a certain amount of flexibility in the features a user
agent must support in order to conform. For example, some user agents may
conform even though they do not support certain
content types such as video or audio. For more information about the scope of conformance claims, please see the section on
conformance.
People with (or without) disabilities access the Web with widely varying
sets of capabilities, software, and hardware. Some users with disabilities:
- May not be able to see, hear, move, or may not be able to process some
types of information easily or at all.
- May have difficulty reading or comprehending text.
- May not have or be able to use a keyboard or mouse.
This document does not include requirements to meet all known accessibility
needs. Some known limitations of this document include the following:
- Braille. This document does not address braille rendering.
- Synthesized speech. This document includes only three checkpoints related
to synthesized speech (checkpoints 4.11,
4.12 and
4.13).
- Size and color of non-text content. This document includes some checkpoints
to ensure that the user is able to control the size and color of visually
rendered text content (checkpoints 4.1 and
4.3). This document does not in general address control of the size and
color of visually rendered non-text
content. Note: Resizing capabilities may be
required for conformance to other specifications (e.g., SVG [SVG]).
- Input modalities. This document only includes requirements for keyboard,
pointing device, and voice input modalities. This document includes several
checkpoints related to voice input as part of general input requirements (e.g.,
use of standard APIs and configurability of voice input).
This document does not otherwise address voice-based navigation or control.
Note: The UAWG intends to coordinate
further work on the topics of voice input and synthesized speech output with
groups in W3C's Voice Browser
Activity.
- Time. This document includes requirements for control of some time
parameters (including
checkpoint 2.2, checkpoint
4.4, checkpoint 4.5,
and checkpoint 4.11).
The requirements are for time parameters that the user agent recognizes and
controls. This document does not include requirements for control of
server-side time parameters.
- Security. This document does not address security issues that may arise as
a result of these requirements. For instance, requirements that software be
able to read and write content and user interface information through APIs
raise security issues. See the section on
restricted functionality and conformance.
- Intellectual property. This document does not address intellectual property
issues that may arise as a result of these requirements.
Considerable effort has been made to ensure that the requirements of this
document are compatible with other good software design practices. However,
this document does not purport to be a complete guide to good software design.
For instance, 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 for User Agent Accessibility Guidelines 1.0"
[UAAG10-TECHS] includes some references to general software design
guidelines and platform-specific accessibility guidelines (see checkpoint 5.12). To ensure the
accessibility of any piece of software, and in particular the user interface,
people with disabilities should be involved in its design and testing.
Installation is an important aspect of both accessibility and general
software usability. On platforms where a user can install a user agent, the
installation (and update) procedures need to be accessible. This document does
not include a checkpoint requiring that installation procedures be accessible.
Since this document considers installation to be part of software usage, the
different aspects of installation (user interface, documentation, system
conventions, etc.) are already covered by the complete set of checkpoints.
Many users without disabilities 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 are likely to
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 are likely to benefit from the same features that provide access to
people who cannot use a mouse or keyboard due to a visual, hearing, or physical
disability.
- They may not understand fluently the natural language of spoken content.
These users are likely to benefit from the same visual rendering of text equivalents that make spoken language
accessible to people with a hearing disability.
Software that satisfies the requirements of this document will also be more
flexible, manageable, extensible, and beneficial to all users. For example, a
user agent architecture that allows programmatic access to content and the
user interface will encourage software modularity and reuse, and
will enable operation by scripting tools and automated test engines in addition
to assistive technologies.
The ten 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 satisfied by the user agent (i.e., the "subject of the claim) for the purposes of conformance. The "user agent" may consist of more than
one software component, as explained in the section on well-formed conformance claims.
- The priority of the checkpoint.
- Content type labels (zero or more),
which may be used in a in conformance claim.
- Informative notes about the checkpoint. These notes do not
state requirements that must be satisfied as part of conformance; they are
informative only. They are meant to clarify the scope of the checkpoint through
further description, examples, cross references, and commentary.
Note: Some checkpoints in this document are more general than others,
and some may overlap in scope. Therefore, a checkpoint may be identified as an
"important special case" of one or more other checkpoints.
- 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 a clear minimal requirement for
the purposes of conformance. Both this document and
"Techniques for User Agent Accessibility Guidelines 1.0"
[UAAG10-TECHS] suggest how user agent developers may surpass the
minimal requirements. Note: In some cases, though the
requirement of a checkpoint may be clear, without documentation from vendors
(e.g., about implemented APIs), it may be difficult to verify that the
subject of a conformance claim 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 need to ensure redundancy in the
user interface. The user has to 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.). The user also requires access
to the full benefit of Web content through each of at least three modalities --
visually-displayed text, synthesized speech, and braille.
Text content has the accessibility advantage of being available to
people who use graphical displays, speech synthesizers, and braille
displays.
People who cannot or do not use a mouse have to be able to operate the user
interface with the keyboard, through voice input, a head wand, touch screen, or
other device. Keyboard operation (using as few keystrokes as possible) 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 specialized input devices
may reuse the keyboard API.
To ensure that assistive
technologies can both operate the user agent programmatically (e.g.,
through simulated keyboard events) and monitor user agent output, developers
are expected to use each API appropriately. Developers should not, for
example, pre-rasterize text (i.e.,
turn it into a bitmap for rendering rather using the system's text drawing
facilities) since doing so may prevent assistive technologies from being able
to render the text as speech or braille.
Checkpoints for user interface accessibility:
-
1.1 Ensure that the user can operate the user agent fully through
keyboard input alone, pointing device input alone, and voice input alone. [Priority 1]
- Note: For example, ensure that through all three input
modalities, the user can interact with
active elements, select content, navigate viewports, configure the
user agent, access documentation, install the user agent, etc. A user agent may
claim conformance to this document without
satisfying the pointing device and voice portions of this checkpoint. See the
section on input modality labels.
-
Techniques for checkpoint 1.1
-
1.2 Ensure that the user can interact with all
active elements through keyboard input
alone, pointing device input alone, and voice input alone. [Priority 1]
- Note: A user agent may claim
conformance to this document without satisfying the pointing device and
voice portions of this checkpoint. See the section on input modality labels. This checkpoint is an
important special case of
checkpoint 1.1.
-
Techniques for checkpoint 1.2
- 1.3 Ensure that every message (e.g., prompt, alert,
notification, etc.) that is a non-text
element and is part of the user
agent user interface has a text
equivalent. [Priority 1]
- Note: For example, if the user is
alerted of an event by an audio cue, a visually-rendered text equivalent in the
status bar would satisfy this checkpoint. Per checkpoint 5.4, a text equivalent for each such message must
be available through a standard API.
See also checkpoint 5.5.
- Techniques for
checkpoint 1.3
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 speech and prerecorded audio), tactile (braille), graphical, or a mix of some of these. Authors
and user agents share responsibility for ensuring redundant modes. Web content
authors specify
equivalents, 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 content generated by the user agent
itself. User agents should allow users to specify whether content should be
rendered,
equivalents for that content should be rendered, or both.
Ensuring access to equivalents 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 recognized
equivalents, attributes, style sheets, etc. This checkpoint does not
require that all content be available in every
viewport. A document
source view is an important part of a solution for providing access
to content, but is not a sufficient solution on its own for all content. See 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 controlled by the user agent, allow
the user to configure
the user agent to pause the presentation automatically and await user input
before proceeding. [Priority 1]
- Note: In this configuration, the user
agent may have to pause the presentation more than once, depending on the
number of times input is requested. In SMIL 1.0 [SMIL], for example, the
"
begin
", "end
", and "dur
" attributes
synchronize presentation components. This checkpoint does not apply when the user agent cannot recognize the time interval in the presentation
format, or when the user agent cannot control the timing (e.g., because it is
controlled by the server).
- Techniques
for checkpoint 2.2
- 2.3 Provide easy access to each
equivalent and each equivalency
target through at least one of the following mechanisms: (1)
allowing configuration to render the equivalent instead of the equivalency
target; (2) allowing configuration to render the equivalent in addition to the
equivalency target; (3) allowing the user to select the equivalency target and
then inspect its equivalents; (4) providing a direct link to the equivalent in
content, just before or after the equivalency target in document order. [Priority 1]
- Note: For example, if an image in an
HTML document has text
equivalents, provide access to them (1) by replacing the image with
the rendered equivalents, (2) by rendering the equivalents near the image, (3)
by allowing the user to select the image and then inspect its equivalents, or
(4) by allowing the user to follow readily available links to the
equivalents.
- Techniques
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. [Priority 1]
- Content type labels:
NoVideo,
NoAudio.
-
Techniques for checkpoint 2.4
- 2.5 Respect author-specified
synchronization cues during rendering.
[Priority 1]
- Content type labels:
NoVideo,
NoAudio.
- Techniques
for checkpoint 2.5
- 2.6 Allow configuration to generate repair text when the user agent recognizes that the author has failed to
provide a required
equivalent. If the content missing an equivalent is included by URI
reference, base the repair text on the URI reference and content type.
Otherwise, base the repair text on element type information. [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 by this document to generate repair text. See also checkpoint 2.7.
- Techniques for
checkpoint 2.6
- 2.7 Allow configuration so that when the author
has specified an empty text
equivalent for non-text
content, the user agent generates no
repair text or generates repair text as required by checkpoint 2.6. [Priority 3]
- Note: An empty text equivalent (e.g.,
alt=""
)
is considered to be a valid text
equivalent in some authoring scenarios. For instance, when some non-text
content has no other function than pure decoration, or an image is
part of a "mosaic" of several images and doesn't make sense out of the mosaic.
Please refer to the Web Content Accessibility Guidelines 1.0 [WCAG10] for
more information about text equivalents. See also checkpoint 2.6.
- Techniques for
checkpoint 2.7
-
2.8 Allow the user to configure
the user agent not to render content in unsupported natural
languages. Indicate to the user in context that author-supplied
content has not been rendered.
[Priority 3]
- Note: For example, use a text
substitute or accessible graphical icon to indicate that content in a
particular language has not been rendered. This checkpoint does not require the
user agent to allow different configurations for different natural
languages.
-
Techniques for checkpoint 2.8
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 re-render the text every time it blinks.
Distracting background images, colors, or sounds may 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 does not render portions of that resource
that are of a particular type, or the user agent will render those portions in
a way that does not pose accessibility problems.
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. In this configuration, provide
an option to alert the user when a background image is available (but has not
been rendered). [Priority 1]
- Content type labels:
NoImage.
- Note: This checkpoint only requires control of background
images for "two-layered renderings", i.e., one rendered background image with
all other content rendered "above it". When background images are not rendered,
user agents should render a solid background color (see checkpoint 4.3). In this
configuration, the user agent is not required to retrieve background images
from the Web.
-
Techniques for checkpoint 3.1
- 3.2
Allow the user to configure
the user agent not to render audio, video, or animated images except on
explicit request from the user. In this configuration, provide an option to
render a
placeholder in context for each unrendered source of audio, video,
or animated image. When placeholders are rendered, allow the user to activate
each placeholder individually and replace it with the original author-supplied
content. [Priority 1]
- Content type labels:
NoAnimation, NoVideo,
NoAudio.
- Note: This checkpoint requires configuration for content
rendered without any user interaction (including content rendered on load or as
the result of a script) as well as content rendered as the result of user
interaction that is not an explicit request (e.g., when the user activates a
link). Activation of a
placeholder is considered an explicit user request to render the
original content. When configured not to render content except on explicit user
request, the user agent is not required to retrieve the audio, video, or
animated image from the Web until requested by the user. See also checkpoint 4.5, checkpoint 4.9 and checkpoint
4.10.
-
Techniques for checkpoint 3.2
- 3.3
Allow the user to configure
the user agent to render animated or blinking text as motionless, unblinking
text. [Priority 1]
- Content type labels:
NoVisualText.
- Note: This checkpoint does not
apply for blinking and animation effects that are caused by mechanisms that
the user agent cannot
recognize.
-
Techniques for checkpoint 3.3
-
3.4 Allow the user to configure
the user agent to render blinking images as motionless, unblinking images.
[Priority 1]
- Content type labels:
NoAnimation.
-
Techniques for checkpoint 3.4
- 3.5 Allow the user to configure the user agent not to execute any
scripts or applets. In this configuration, provide an option to alert the user
when scripts or applets are available (but have not been executed). [Priority 1]
- Techniques
for checkpoint 3.5
-
3.6 Allow
configuration so that an author-specified "client-side redirect"
(i.e., one initiated by the user agent, not the server) does not change content except on explicit user request. Allow the user to access
the new content on demand (e.g., by following a link or confirming a prompt).
The user agent is not required to provide these functionalities for client-side
redirects that occur instantaneously (i.e., when there is no delay before the
new content is retrieved).
[Priority 2]
-
Techniques for checkpoint 3.6
-
3.7 Allow
configuration so that author-specified content refreshes do not
change
content except on explicit
user request. Allow the user to request the new content on demand
(e.g., by following a link or confirming a prompt). Alert the user, according
to the schedule specified by the author, whenever fresh content is available
(to be obtained on explicit user request).
[Priority 2]
-
Techniques for checkpoint 3.7
- 3.8 Allow the user to configure the user agent not to render images.
In this configuration, provide an option to render a
placeholder in context for each unrendered image. When placeholders
are rendered, allow the user to activate each placeholder individually and
replace it with the original author-supplied content.
[Priority 2]
- Content type labels:
NoImage.
- Techniques for
checkpoint 3.8
Providing access to content (see guideline 2) includes enabling users to configure its rendering. Users with low vision
may require that text be rendered at a size larger than the size specified by
the author or the user agent's default. Users with color blindness may need to
impose or prevent certain color combinations.
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 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. Users need to be alerted to changes to
content or viewports
that the users did not initiate (e.g., when a viewport opens
automatically).
Note: The checkpoints in this guideline apply to all
content, including
equivalents.
Checkpoints for visually rendered text (content accessibility):
- 4.1
Allow the user to configure
globally and control the
reference size of rendered text, with an option to override reference sizes
specified by the author or user agent defaults. Allow the user to choose from
among the full range of font sizes supported by the system. [Priority 1]
- Content type labels:
NoVisualText.
- Note: The reference size of rendered
text corresponds to the default value of the CSS2 'font-size' property, which
is 'medium' (refer to CSS2 [CSS2], section 15.2.4). The default
reference size of rendered text may vary among user agents. User agents may
offer different mechanisms to allow the user to control the size of rendered
text, for example by allowing the user to change the font size or by allowing
the user to zoom or magnify content (refer, for example to the Scalable Vector
Graphics specification
[SVG]).
-
Techniques for checkpoint 4.1
-
4.2 Allow the user to configure globally the font family of all
rendered text, with an option to override font families specified by the author
or user agent defaults. Allow the user to choose from among the full range of
font families supported by the system.
[Priority 1]
- Content type labels:
NoVisualText.
- Note: For example, allow the user to
specify that all
text must be rendered in a particular
sans-serif font family. For text that
cannot be rendered properly using the user's selected font family, the user
agent may select an alternative font family.
-
Techniques for checkpoint 4.2
- 4.3
Allow the user to configure
globally the foreground and background color of all rendered text,
with an option to override foreground and background colors specified by the
author or user agent defaults. Allow the user to choose from among the full
range of colors supported by the system.
[Priority 1]
- Content type labels:
NoColorText.
- Note: User configuration of foreground
and background colors may result in the inability to distinguish ordinary text
from selected text, focused text, etc. See checkpoint 8.2 for more information about highlight
styles.
-
Techniques for checkpoint 4.3
Checkpoints for
multimedia presentations and other presentations that change
continuously over time (content accessibility):
- 4.4 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
prerecorded audio
track including audio-only presentations, provide at least one
setting between 75% and 80% of the original speed. When the user agent allows
the user to slow the visual track of a synchronized multimedia presentation to
between 100% and 80% of its original speed, synchronize the visual and audio
tracks. Below 80%, the user agent is not required to render the audio track. The user agent is not required to
satisfy this checkpoint for audio, video and animations whose recognized role is to create a purely stylistic
effect. [Priority 1]
- Content type labels:
NoAnimation, NoVideo,
NoAudio.
- Note: Purely stylistic effects include background sounds,
decorative animated images, and effects caused by style sheets. The style
exception of this checkpoint is based on the assumption that authors have
satisfied the requirements of the "Web Content Accessibility Guidelines 1.0"
[WCAG10] not to convey information through style alone (e.g.,
through color alone or style sheets alone). See also checkpoint
4.7.
- See also checkpoint
2.5.
- Techniques
for checkpoint 4.4
- 4.5 Allow the user to stop, pause,
resume, fast advance, and fast reverse audio, video, and animations that last
three or more seconds at their default playback rate. The user agent is not
required to satisfy this checkpoint for audio, video and animations whose recognized role is to create a purely stylistic
effect. [Priority 1]
- Content type labels:
NoAnimation, NoVideo,
NoAudio.
- Note: See
checkpoint 4.4 for more information about the exception for purely
stylistic effects. This checkpoint applies to content that is rendered
automatically or on request from the user. Enable control of each independent
source recognized as distinct. Respect synchronization cues per checkpoint 2.5. See also checkpoint 3.2.
-
Techniques for checkpoint 4.5
- 4.6 For
graphical viewports, allow the user to position text
transcripts,
collated text transcripts, and
captions in the viewport. Allow the user to choose from among the
same range of positions available to the author (e.g., the range of positions
allowed by the markup or style language).
[Priority 1]
-
Techniques for checkpoint 4.6
-
4.7 Allow the user to slow the presentation rate of audio, video and
animations not covered by
checkpoint 4.4. The same speed percentage requirements of checkpoint 4.4 apply. [Priority 2]
- Content type labels:
NoAnimation, NoVideo,
NoAudio.
- Note: User agents automatically satisfy
this checkpoint if they satisfy
checkpoint 4.4 for every audio, video, and animation.
-
Techniques for checkpoint 4.7
-
4.8 Allow the user to stop, pause, resume, fast advance, and fast
reverse audio, video, and animations not covered by checkpoint 4.5. [Priority 2]
- Content type labels:
NoAnimation, NoVideo,
NoAudio.
- Note: User agents automatically satisfy
this checkpoint if they satisfy checkpoint 4.5 for every audio, video, and animation.
-
Techniques for checkpoint 4.8
Checkpoints for audio volume control (content accessibility):
-
4.9 Allow the user to configure globally and
control the volume of all audio, with an option to override audio
volumes specified by the author or user agent defaults. The user must be able
to choose zero volume (i.e., silent). [Priority 1]
- Content type labels:
NoAudio.
- Note: User agents should allow
configuration and control of volume through available system-level
controls.
-
Techniques for checkpoint 4.9
-
4.10 Allow the user to control
independently the volumes of distinct audio sources synchronized to play
simultaneously. [Priority 1]
- Content type labels:
NoAudio.
- Note: Sounds that play at different times are
distinguishable and therefore independent control of their volumes is not part
of this checkpoint (volume control per checkpoint 4.9 suffices). The user agent may satisfy this
checkpoint by allowing the user to control independently the volumes of all
distinct audio sources. The user control required by this checkpoint includes
the ability to override author-specified volumes for the relevant sources of
audio. See also checkpoint
4.12.
-
Techniques for checkpoint 4.10
Checkpoints for synthesized speech (content accessibility):
-
4.11 Allow the user to configure and
control synthesized speech playback rate according to the full range
offered by the speech synthesizer.
[Priority 1]
- Content type labels:
NoSpeech.
- Note: The range of playback rates
offered by the speech synthesizer may depend on the natural language.
-
Techniques for checkpoint 4.11
-
4.12 Allow the user to control
synthesized speech volume independent of other sources of audio. [Priority 1]
- Content type labels:
NoSpeech.
- Note: The user control required by this checkpoint
includes the ability to override author-specified speech volume. See also checkpoint
4.10.
-
Techniques for checkpoint 4.12
-
4.13 Allow the user to configure
synthesized voice gender, pitch, pitch range, stress, richness, speech
dictionary, and handling of spelling, punctuation, and number processing
according to the full range of values offered by the speech synthesizer. [Priority 2]
- Content type labels:
NoSpeech.
- Note: Many speech synthesizers allow
users to choose from among preset options that control different voice
parameters (gender, pitch range, stress, richness, etc.) as a group. When using
these synthesizers, allow the user to choose from among the full range of
preset options (e.g., "adult male voice", "female child voice", "robot voice",
etc.). Ranges of values for these characteristics may vary among speech
synthesizers. For information about these synthesized speech characteristics,
please refer to descriptions in section 19.8 of Cascading Style Sheets Level 2
[CSS2].
-
Techniques for checkpoint 4.13
Checkpoints for user interface accessibility:
- 4.14
For user agents that support
style sheets, allow the user to choose from (and apply) 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 4.14
-
4.15 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 4.15
-
4.16 Ensure that when a viewport's
selection or content
focus changes, it is in the viewport
after the change. [Priority 2]
- Note: For example, if users navigating
links move to a portion of the document outside a graphical viewport, the
viewport should scroll to include the new location of the focus. Or, for users
of audio viewports, allow configuration to render the selection or focus
immediately after the change.
-
Techniques for checkpoint 4.16
- 4.17 For graphical user interfaces,
allow the user to configure the user agent so that the viewport with the
current focus remains "on top" of all
other viewports with which it overlaps.
[Priority 2]
- Techniques
for checkpoint 4.17
- 4.18 Allow the user to configure the user agent to only open viewports
on explicit
user request. In this configuration, instead of opening a viewport
automatically, alert the user and allow the user to open it on demand (e.g., by
following a link or confirming a prompt). Allow the user to close viewports. If
a viewport (e.g., a frame set) contains other viewports, these requirements
only apply to the outermost container viewport.
[Priority 2]
- Note: User creation of a new viewport (e.g., empty or with
a new resource loaded) through the user agent's user interface constitutes an
explicit user request. See also checkpoint 4.15 (for control over changes of focus when a
viewport opens) and checkpoint
5.5.
- Techniques
for checkpoint 4.18
- 4.19
Allow configuration so the user is prompted to
confirm any viewport that closes without explicit user request. [Priority 3]
-
Techniques for checkpoint 4.19
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.
- 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. 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
reimplement.
Checkpoints for communication with other software:
- 5.1 Provide programmatic read access to
HTML and XML
content by conforming to the following modules of the W3C Document
Object Model DOM Level 2 Core
Specification [DOM2CORE] and exporting the
interfaces they define: (1) the Core module for HTML; (2) the Core and XML
modules for XML. [Priority 1]
- Note: Please refer to the "Document
Object Model (DOM) Level 2 Core Specification" [DOM2CORE]
for information about HTML and XML
versions covered.
- 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 following modules of the W3C Document Object Model DOM Level 2 Core Specification
[DOM2CORE] and exporting the interfaces they define: (1) the Core
module for HTML; (2) the Core and XML modules for XML.
[Priority 1]
- Note: For example, if the user
interface allows users to complete HTML forms, this must
also be possible through the required DOM
APIs. Please refer to the "Document
Object Model (DOM) Level 2 Core Specification" [DOM2CORE]
for information about HTML and XML
versions covered.
- 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.
-
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 defined for a specific
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 alert of
changes to
content and
user interface controls (including
selection, content
focus, and user
interface focus).
[Priority 1]
- Note: For instance, when user
interaction in one frame causes automatic changes to content in another,
provide programmatic alert through standard APIs. Use the standard APIs required by the checkpoints of guideline 5.
- Techniques for
checkpoint 5.5
- 5.6
Implement standard accessibility APIs (e.g., of the operating system and
supported programming languages). Where these APIs do not enable the user agent
to satisfy the requirements of this document, use the
standard input and output APIs of the
operating system and supported programming languages.
[Priority 1]
- Note: Accessibility APIs enable
assistive technologies to monitor input and output events. As part of
satisfying this checkpoint, the user agent needs to ensure that text content is available as text through these
APIs (and not, for example, as a series of strokes drawn on the screen).
-
Techniques for checkpoint 5.6
- 5.7 Implement
the operating system's
standard APIs for the keyboard. [Priority 1]
- Note: An operating system may define more than one
standard API for the keyboard. For instance, for Japanese and Chinese, input
may be processed in two stages, with an API for each. This checkpoint is an
important special case of
checkpoint 1.1. See
also checkpoint 9.4.
- Techniques for
checkpoint 5.7
- 5.8 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 5.8
- 5.9 For user agents that implement Cascading Style Sheets
(CSS), provide programmatic access to those style sheets by
conforming to the CSS module of the W3C Document Object Model (DOM) Level 2 Style Specification
[DOM2STYLE] and exporting the interfaces it defines. [Priority 2]
- Note: As of the publication of this
document, Cascading Style Sheets (CSS) are defined by CSS
Level 1
[CSS1] and CSS Level 2 [CSS2]. Please refer to the "Document
Object Model (DOM) Level 2 Style Specification"
[DOM2STYLE] for information about CSS versions
covered.
- Techniques
for checkpoint 5.9
Checkpoints for user interface accessibility:
-
5.10 Follow operating system conventions that benefit accessibility
when
implementing the
selection, content
focus, and user
interface focus.
[Priority 1]
- Note: This checkpoint is an important special case of checkpoint 5.12. See also checkpoint 7.1.
-
Techniques for checkpoint 5.10
-
5.11 Ensure that default input configurations do not 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]. See also checkpoint
9.4.
-
Techniques for checkpoint 5.11
- 5.12 Follow operating system conventions
that benefit accessibility. In particular, follow conventions that benefit
accessibility 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]. See also checkpoint 5.11.
- Techniques
for checkpoint 5.12
-
5.13 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 5.12. See also checkpoint
9.4.
-
Techniques for checkpoint 5.13
Developers should implement open specifications. Conformance to open
specifications benefits 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 recommends conformance to 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. This review includes review from
stakeholders in accessibility.
- W3C specifications are developed in a consensus process (refer to the
process defined by the W3C Process Document [W3CPROCESS]). W3C encourages
the public to review and comment on these specifications (public Working
Drafts, Candidate Recommendations, and Proposed Recommendations). 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 implemented specifications (markup languages,
style sheet languages, metadata languages, graphics formats, etc.). The
accessibility features of a specification are those identified as such and
those that satisfy all of the requirements of the "Web Content
Accessibility Guidelines 1.0" [WCAG10].
[Priority 1]
- Note: This checkpoint applies to both W3C-developed and
non-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, conform to HTML 4 [HTML4], XHTML 1.0
[XHTML10], or XML 1.0 [XML]. For style sheets, conform to
CSS ([CSS1], [CSS2]). For mathematics, conform to
MathML
[MATHML]. For synchronized multimedia, implement
SMIL 1.0
[SMIL]. For information about programmatic access to
HTML and XML content, see guideline 5. User agents may
conform to other specifications in addition to those required by this
checkpoint. For reasons of backward compatibility, user agents should continue
to
implement deprecated features of
specifications. Information about deprecated language features is generally
part of the language's specification.
-
Techniques 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 efficiently. 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 also benefits 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), to users
with visual disabilities, and also benefits "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, see 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.).
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, restore the point of
regard.
-
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: The set of navigable elements
required by this checkpoint must include active elements and may include
non-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]
- Note: The set of navigable elements
required by this checkpoint must include active elements and must not include
non-active elements.
- Techniques
for checkpoint 7.4
- 7.5 Allow the user to search within rendered text
content for a sequence of characters from the
document character set. Allow the user to start a forward search (in
document order) from any selected or focused location in content. When there is
a match (1) move the viewport so that the matched text content is within it,
and (2) allow the user to search for the next instance of the text from the
location of the match. Alert the user when there is no match. If the search
wraps back to the beginning of content, alert the
user prior to wrapping. Provide a case-insensitive search option for text in scripts (i.e., writing systems) where case is
significant. [Priority 2]
- Note: The default search starting point should be the
beginning of content. Use operating system conventions for indicating the
result of a search (e.g., selection
or content
focus). A wrapping search is one that restarts automatically at the
beginning of content once the end of content has been reached.
- Techniques for
checkpoint 7.5
- 7.6 Allow the user to navigate efficiently
to and among important structural elements. Allow forward and backward
sequential navigation to important structural elements. [Priority 2]
- Note: This specification intentionally
does not identify which "important elements" must be navigable as this will
vary according to markup language. What constitutes "efficient navigation" may
depend on a number of factors as well, including the "shape" of content (e.g.,
serial navigation of long lists is not efficient) and desired granularity
(e.g., among tables, then among the cells of a given table). Refer to the
Techniques document [UAAG10-TECHS] for
information about identifying and navigating important elements. See also checkpoint
7.7.
- Techniques for
checkpoint 7.6
- 7.7
Allow the user to configure and
control the set of important elements required by checkpoint 7.6 and checkpoint 8.4. Allow the
user to include and exclude element types in the set of elements. [Priority 3]
- Note: For example, allow the user to navigate only
paragraphs, or only headings and paragraphs, etc. See also checkpoint 5.4.
-
Techniques for checkpoint 7.7
All users require clues to help them understand their "location" when
browsing: where they are, how they got there, where they can go, what's nearby,
etc. Some mechanisms that provide such clues include:
- information about browsing context such as proportional scroll bars, a
visually
highlighted selection, a history mechanism, the title of the current
document or frame, etc. These clues must be available in a device-independent
manner;
- information about elements, such as the dimensions of a table, the length
of an audio clip, the structure of a form, whether following a link will
involve a fee, etc.
- information about relationships among elements, such as between table cells
and related table headers.
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.
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, user
agents rendering in two dimensions may satisfy this checkpoint by rendering a
table as a grid and by ensuring that users can find headers associated with
cells. However, for large tables or small viewports, allowing the user to query
cells for information about related headers may improve access. See also checkpoint 5.3.
This checkpoint is an important special case of checkpoint 2.1.
- Techniques for
checkpoint 8.1
- 8.2 Ensure that all of the default highlight styles for the selection,
content focus, active
elements, recently visited links, and fee
links (1) do not rely on color alone, and (2) differ from each
other, and not by color alone.
[Priority 1]
- Note: For instance, by default a
graphical user agent may present the selection using color and a dotted
outline, the focus using a solid outline, active elements as underlined in
blue, recently visited links as dotted underlined in purple, and fee links
using a special icon or flag to draw the user's attention.
- Techniques
for checkpoint 8.2
- 8.3 Provide a mechanism for highlighting all
active elements, recently visited links, and fee
links, and allow the user to configure the highlight styles. The
highlight mechanism must not rely on color alone. For graphical viewports, if
the highlight mechanism involves colors, fonts, or text
decorations, allow the user to choose from among the full range of
colors, fonts, or text decorations supported by the system. [Priority 2]
- Note: Examples of highlight mechanisms include foreground
and background color variations, font variations, underlining, distinctive
voice pitches, rectangular boxes, etc.
- Techniques
for checkpoint 8.3
- 8.4
Make available to the user an "outline" view of
content, composed of labels for important structural elements (e.g.,
heading text, table titles, form titles, etc.).
[Priority 2]
- Note: This checkpoint is meant to
provide the user with a simplified view of content (e.g, a table of contents).
What constitutes a label is defined by a markup language specification. For
example, in HTML, a heading (
H1
-H6
) is a label for
the section that follows it, a CAPTION
is a label for a table, the
"title
" attribute is a label for its element, etc. A label is not
required to be
text only. For important elements that do
not have associated labels, user agents may generate labels for the outline
view. For information about what constitutes the set of important structural
elements, please see the Note following checkpoint 7.6. By making the outline view navigable, it is
possible to satisfy this checkpoint and checkpoint 7.6 together: Allow users to navigate among the
important elements of the outline view, and to navigate from a position in the
outline view to the corresponding position in a full view of content. See also checkpoint
7.7.
-
Techniques for checkpoint 8.4
- 8.5 To help the user decide whether to
traverse a link, make available the following information about it: link
content, link title, whether the link is internal to the local resource,
whether the user has traversed the link recently, whether traversing it may
involve a fee, and information about the type, size, and natural language of
linked Web resources. The user agent is not required to compute or make
available information that requires retrieval of linked
Web resources.
[Priority 3]
- Techniques for
checkpoint 8.5
Checkpoints for user interface accessibility:
-
8.6 Provide a mechanism for
highlighting the selection
and content
focus, and allow the user to configure the highlight styles. The
highlight mechanism must not rely on color alone. For graphical viewports, if
the highlight mechanism involves colors or text decorations, allow the user to choose from
among the full range of colors or text decorations supported by the system.
[Priority 1]
- Note: Examples of highlight mechanisms include foreground
and background color variations, underlining, distinctive voice pitches,
rectangular boxes, etc. Because the selection and focus change frequently, user
agents should not highlight them using mechanisms (e.g., font size variations)
that cause content to reflow as this may disorient the user. See also checkpoint
5.10.
-
Techniques for checkpoint 8.6
- 8.7 Provide a mechanism for highlighting the current viewport. For graphical viewports, the default
highlight mechanism must not rely on color alone.
[Priority 1]
- Note: This includes highlighting and
identifying frames. This checkpoint is an important special case of checkpoint 1.1. See also
to checkpoint checkpoint
5.12.
-
Techniques for checkpoint 8.7
- 8.8 Allow configuration so the user is
prompted to confirm any form submission not
caused by explicit
user request to activate a form submit control. [Priority 2]
- 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 8.8
- 8.9 Allow configuration so the user is prompted to confirm any payment resulting from
activation of a fee link.
[Priority 2]
- Techniques for
checkpoint 8.9
- 8.10 Indicate the relative position of
the viewport in rendered content (e.g., the proportion of an
audio or video clip that has been played, the proportion of a Web page that has
been viewed, etc.). [Priority 3]
- 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 8.10
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:
-
9.1 Provide information to the user about current user preferences
for input
configurations.
[Priority 1]
- Note: To satisfy this checkpoint, the
user agent may make available binding information in a centralized fashion
(e.g., a list of bindings) or a distributed fashion (e.g., by listing keyboard
shortcuts in user interface menus).
-
Techniques for checkpoint 9.1
-
9.2 Provide a centralized view of the current author-specified input
configuration bindings.
[Priority 2]
- Note: For example, for HTML documents,
provide a view of keyboard bindings specified by the author through the
"accesskey"
attribute. The intent of this checkpoint is to centralize
information about author-specified bindings so that the user does not have to
read the entire content first to find out what bindings are available. The user
agent may satisfy this checkpoint by providing different views for different
input modalities (keyboard, pointing device, voice, etc.).
-
Techniques for checkpoint 9.2
- 9.3 Allow the user to override any
binding that is part of the user agent default input
configuration. Allow the user to override any binding in the default
keyboard configuration with a binding of a single key and (possibly zero)
modifier keys. Allow the user to assign a single key binding (with zero
modifier keys) to at least a majority of the functionalities available in the
default keyboard configuration. The user agent is not required to allow the
user to override standard bindings for the operating system (e.g., for access
to help). [Priority 2]
- Note: The override requirement only
applies to bindings for the same input modality (i.e., the user must be able to
override a keyboard binding with another keyboard binding). This checkpoint
does not require single-key bindings for character input, only for the
activation of user agent functionalities. See also checkpoint 9.4, checkpoint 9.6, and checkpoint 10.3.
- Techniques
for checkpoint 9.3
- 9.4
Ensure that the default input
configuration includes bindings for the following functionalities
required by other checkpoints in this document: move focus to next active
element; move focus to previous active element; activate focused link; search
for text; search again for same text; next history state (forward); previous
history state (back); increase size of rendered text; decrease size of rendered
text; increase global volume; decrease global volume; (each of) stop, pause,
resume, fast advance, and fast reverse selected audio, video, and animation. If
the user agent supports
the following functionalities, the default input configuration must also
include bindings for them: enter URI for new resource; add to favorites (i.e.,
bookmarked resources); view favorites; stop loading resource; reload resource;
refresh rendering; forward one viewport; back one viewport; next line; previous
line. [Priority 2]
- Note: This checkpoint does not make any
requirements about the ease of use of default input configurations, though
clearly the default configuration should include single-key bindings and allow
easy operation. Ease of use is ensured by the configuration requirements of checkpoint 9.3.
-
Techniques for checkpoint 9.4
- 9.5 For the configuration requirements of
this document, allow the user to save user preferences in at least one user profile. Allow users to choose 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
alerts.
- Techniques for
checkpoint 9.5
- 9.6 For graphical user interfaces,
allow the user to configure
the position of controls on tool bars of the user agent user interface, to add 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 9.3.
-
Techniques for checkpoint 9.6
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 through key strokes.
See also checkpoint
5.12.
Checkpoints for accessible documentation:
- 10.1 Ensure that at least one version of
the product
documentation conforms to at least Level Double-A of the Web Content
Accessibility Guidelines 1.0 [WCAG10].
[Priority 1]
- Techniques
for checkpoint 10.1
-
10.2
Document all user agent features that benefit accessibility. [Priority 1]
- Note: For example, review the
documentation or help system to ensure that it includes information about the
functions and capabilities of the user agent that are required by WAI Guidelines.
-
Techniques for checkpoint 10.2
-
10.3
Document the default input configuration (e.g., the default keyboard
bindings). [Priority 1]
-
Techniques for checkpoint 10.3
-
10.4 In a dedicated section of the
documentation, describe all features of the user agent that benefit
accessibility. [Priority 2]
- Note: This is a more specific
requirement than
checkpoint 10.2.
-
Techniques for checkpoint 10.4
- 10.5 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 10.5
This normative section explains how to make a
valid claim that a user agent conforms to this document. Here is an example
of well-formed claim (expressed in HTML):
<p>On 13 January 2001,
Project X (version 2.3) running on MyOperatingSystem (version 4.2) 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-UAAG10-20010113, level Double-A. Unsupported
content types: NoVideo, NoSpeech. Unsupported input modalities: NoVoice. (see
section 3.1 of the UAAG 1.0). The <a
href="http://example.com/checkpoints">list of checkpoints that do not
apply</a> is available online.</p>
The terms "must", "should", and "may" (and related terms) are used in this
document in accordance with RFC 2119 [RFC2119].
This section uses the expression "subject of a claim" to refer to a user agent about which someone wishes to claim
some level of conformance to this document. The subject of a claim may be one
or more software components (e.g., a browser plus additional software).
Note: Conformance to the requirements of this document is
expected to be a strong indicator of accessibility, but it is neither a
necessary nor sufficient condition for ensuring the accessibility of software.
Some software may not conform to this document but still be accessible to some
users with disabilities. Conversely, software may conform to this document but
still be inaccessible to some users with disabilities. Please refer to the
section on known limitations of this document.
By default, a user agent conforms to this document if it meets all of the
following conditions:
- It satisfies all of the checkpoints of this document.
- It satisfies requirements for images, video, animations, visually displayed
text (in color), and synthesized speech;
- It is fully operational through keyboard input alone, pointing device input
alone, and voice input alone. Input device requirements are satisfied for all
three input modalities.
It is possible to satisfy fewer checkpoints, support fewer content types,
and support fewer input modalities, and still conform to this document.
However, any departure from the default conformance requirements must be
documented in a well-formed conformance claim.
Claimants may change the scope of a
claim (from the default) through three mechanisms described below: conformance levels, content type labels, and input modality labels. These shorthand
mechanisms are provided to make it easier to publish, read, and compare
claims.
Note: Some checkpoints include more than one requirement.
One requirement of a checkpoint may be within the scope of a claim while
another is out of scope. The conformance claim indicates which requirements the
claimant considers in or out of scope.
This document defines three conformance levels, each of which identifies a
subset of all the checkpoints in the document.
Note: Conformance levels are spelled out in text (e.g.,
"Double-A" rather than "AA") so they may be understood when rendered as
speech.
When the following "content type labels" are part of a conformance claim,
they decrease the scope of a claim with respect to
support for images, video, animations, visually displayed text (in color), and
synthesized speech.
- NoVisualText
- The subject does not satisfy all of the requirements related to the visual
rendering of text for the following checkpoints: 3.3, 4.1, and 4.2.
- NoColorText
- The subject does not satisfy all of the requirements related to text
foreground and background color for the following checkpoint: 8.3.
- NoImage
- The subject does not satisfy all of the requirements related to images for
the following checkpoints: 3.1 and
3.8. To conform, the user agent must
implement at least one image format, unless the claim includes this
label.
- NoAnimation
- The subject does not satisfy all of the requirements related to animated
images for the following checkpoints: 3.2,
3.4, 4.4, 4.5, 4.7, and 4.8. To conform, the
user agent must implement
at least one animation format, unless the claim includes this label.
- NoVideo
- The subject does not satisfy all of the requirements related to video for
the following checkpoints: 2.4,
2.5, 3.2, 4.4, 4.5, 4.7, and 4.8. To conform, the
user agent must implement
at least one video format, unless the claim includes this label.
- NoAudio
- The subject does not satisfy all of the requirements related to audio for
the following checkpoints: 2.4,
2.5, 3.2, 4.4, 4.5, 4.7, 4.8, 4.9, and 4.10. To conform,
the user agent must implement
at least one audio format, unless the claim includes this label.
- NoSpeech
- The subject does not satisfy all of the requirements related to synthesized
speech for the following checkpoints: 4.11,
4.12 and 4.13. To
conform, the user agent must support
synthesized speech, unless the claim includes this label.
For instance, the content type label "NoImage" in a conformance claim means
that the user agent does not satisfy all of the requirements of checkpoint 3.1 and
checkpoint 3.8 that pertain to
images. The user agent may satisfy some of the requirements.
Note: Some of the labels above require implementation of at
least one format (e.g., for images). This document does not require
implementation of specific formats, (e.g., PNG [PNG] versus
SVG
[SVG] for images). However, please see the requirements of checkpoint 6.2.
To conform to this document, a user agent must be fully
operable through the keyboard, and must satisfy the input
device requirements of this document for the keyboard. When the following
"input modality labels" are part of a conformance claim, they decrease the scope of a claim with respect to support for pointing
device input and voice input.
- NoPointer
- The subject does not satisfy all of the input device requirements of this
document for pointing device input. The user agent is not fully operable
through pointing device input alone.
-
NoVoice
- The subject does not satisfy all of the input device requirements of this
document for voice input. The user agent is not fully operable through voice
input alone.
For instance, the absence of the input modality label "NoPointer"
in a conformance claim means that for the claim to be valid, the user agent must satisfy for the input
device requirements of
checkpoint 1.1, checkpoint
5.12, checkpoint 9.3, checkpoint 10.3, (and
all other checkpoints in scope) for the pointing device.
Note: Developers are encouraged to design user agents that
are at least partially operable through all three input modalities.
By default, all checkpoints (or portions of a checkpoint) that are in the scope of a claim are said "to apply" to the subject of
a claim. However, a checkpoint (or portion of a checkpoint) that is in scope
does not apply if any one of the following conditions is met:
- The checkpoint makes requirements for graphical user interfaces or
graphical viewports and the subject of the claim only has audio or tactile user
interfaces or viewports.
- The checkpoint refers to a role of content (e.g., transcript, captions, text equivalent, fee
link, etc.) that the subject of the claim cannot recognize because of how the content has been
encoded in a particular format. 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 a text description embedded without indicative
markup in a nearby paragraph is a text equivalent for the image.
- The checkpoint requires control of a content property that the subject
cannot
recognize because of how the content has
been encoded in a particular format. Some examples of this include:
- captioning information that is "burned" into a video presentation and
cannot be recognized as captions in the presentation format;
- streamed content that cannot be fast advanced or reversed,
- information or relationships encoded in
scripts in a manner that cannot be recognized. For instance, the
requirements of checkpoint
3.3 would not apply for animation effects caused by scripts. Input
configuration bindings (refer to
guideline 9) created through scripts in a manner that the user agent cannot
recognize do not apply.
A well-formed claim must include the following information:
- The date of the claim.
- 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-UAAG10-20010113.
- The conformance level satisfied: "A",
"Double-A", or "Triple-A".
- Information about the subject. The subject of the claim may consist of one
or more software components (e.g., a browser plus a multimedia player plus a
plug-in). For each component, the claim must include the following:
- The product name and version information (version number, minor release
number, and any required patches or updates). The claim must also include the
vendor name if it is required to identify the product.
- The operating system name and version number.
A well-formed claim may include the following information:
- Content type labels, which decrease the
scope of the claim by eliminating checkpoints (or portions of checkpoints) that
make requirements about unsupported content types.
- Input modality labels, which decrease
the scope of the claim for pointing device and voice input by eliminating
checkpoints (or portions of checkpoints) that make requirements about
unsupported input modalities.
- A list of checkpoints that are in scope but do
not apply (i.e., the subject does not satisfy them).
Claimants may use the checklist [UAAG10-CHECKLIST] for
this purpose. Claimants should provide rationale for why a checkpoint doesn't
apply.
There is no restriction on the
format used to make a well-formed claim. For instance, the claim may be
marked up using HTML (see sample claim), or
expressed in the Resource Description Framework (RDF)
[RDF10].
A conformance claim is valid for a given
conformance level if all of the following conditions are met:
- The claim is well-formed, and
- The subject of the claim as a whole satisfies all the applicable checkpoints that are in the scope of the claim.
- At least one representation of any claim that is on the Web conforms to the
Web Content Accessibility Guidelines 1.0 [WCAG10] level A.
It is not currently possible to validate a claim entirely automatically.
Each checkpoint requirement must be satisfied by making information or
functionalities available through the
user interface of the subject of the
claim unless the checkpoint explicitly states that the requirement must be
met by making information available through an application programming
interface (API). These API checkpoints are labeled
"checkpoints for communication with other software."
Note: The subject of the claim may consist of more than one
software component, and taken together they must satisfy all the applicable checkpoints that are in the scope of the claim. This includes assistive
technologies and operating system features that are part of a claim. Some
components may not have to satisfy some requirements as long as the subject
as a whole satisfies them. For instance, a particular component of the
subject may not have to conform to the DOM APIs required by guideline 5 as long as the
subject of the claim as a whole makes all content available through
those APIs.
Note: The more software components the user must install in
order to construct a conforming user agent, the higher the risk of failure.
Failure may be due to inaccessible mechanisms for downloading and installing
plug-ins, or lack of installation access privileges for a computer in a public
space. Ideally, the standard (or, default) user agent installation procedure
should provide and install all components that are part of a conformance
claim.
To satisfy the requirements of this document, developers are encouraged to
adopt operating system conventions and features that benefit accessibility.
When an operating system feature (e.g., the operating system's audio control
feature) is adopted to satisfy the requirements of this document, it is part of
the subject of the claim.
Developers may provide access through the user agent's user interface to
operating system features adopted to satisfy the requirements of this document.
For example, if the user agent adopts the operating system's audio control
feature to satisfy
checkpoint 4.9, the user agent may (but is not required to) include those
controls in its own user interface.
There may be scenarios where a content provider wishes to limit the user's
full access to content. For instance, a content provider may wish to limit
access to content through an API (e.g., to protect intellectual property
rights, or for security reasons), or to provide a "read-only" view (allowing no
user interaction). A valid conformance claim remains valid even when the
functionality of a conforming user agent is restricted in a particular setting.
The validity of a conformance claim will be seriously jeopardized if a user
agent does not meet the requirements of this document for general-purpose
content.
Note: The User Agent Accessibility Guidelines Working Group
recognizes that further work is necessary in the area of accessibility and
digital rights management.
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 paper product documentation).
Claimants (or relevant assuring parties) are solely responsible for the
validity of their claims, keeping claims up to date, and proper use of the conformance icons. As of the publication of this
document, W3C does not act as an assuring party, but it may do so in the
future, or it may 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. Claimants are encouraged to claim
conformance to the most recent "User Agent Accessibility Guidelines 1.0"
Recommendation available.
As part of a conformance claim, people may use a conformance icon (or,
"conformance logo") on a Web site, on product packaging, in documentation, etc.
Each conformance icon (chosen according to the appropriate conformance level) used on the Web 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.
Draft Note: In the event this document becomes a W3C
Recommendation this document will link to the W3C Web site for additional
information about the icons and how to use them.
-
Active element
- An active element is a piece of
content with behaviors that may be activated (or "triggered") either
through the user interface or through an API (e.g., by using scripts).
What constitutes an active element depends on the content. In
HTML 4
[HTML4] documents, for example, active elements include links, image
maps, form controls, element instances with a value for the "longdesc"
attribute, and element instances with scripts (event handlers) explicitly
associated with them (e.g., through the various "on" attributes). The
requirements of this document refer only to active elements that may be recognized through markup (and not, for
example, through scripts or style sheets). Some element instances may be active
at times but not at others (e.g., they may be "deactivated" through scripts, or
they may only be active for a period of time determined by the author).
Potential user interaction with a piece of content does not imply that the
content constitutes an active element. For example, the user may select text an
copy it to the clipboard, but the selected text is not (necessarily) an active
element, because the selection is a functionality provided by the user agent.
For the purposes of this document, markup languages determine which elements
are potentially active elements.
The effect of activation depends on the element. For instance, when a link
is activated, the user agent generally retrieves the linked
Web resource. When a form control is
activated, it may change state (e.g., check boxes) or may take user input
(e.g., a text entry field). See also the definition of
event handler.
Most systems use the content
focus to indicate which active element will be activated on user
demand.
-
Alert
- In this document, "to alert" means to make the user aware
of some event, without requiring acknowledgement. For example, the user agent
may alert the user that new content is available on the server by displaying a
text message in the user agent's status bar.
See checkpoint 1.3 for
requirements about alerts.
- Application
Programming Interface (API), standard input/output/device
API
- An application programming interface (API) defines how
communication may take place between applications.
As part of encouraging interoperability, this document recommends using
standard APIs where possible, although this document does
not define in all cases how those APIs are standardized (i.e., whether they are
defined by specifications such as W3C Recommendations, defined by an operating
system vendor, de facto standards, etc.). Implementing
APIs that are independent of a particular operating system (e.g., the W3C DOM
Level 2 specifications) may reduce implementation costs for multi-platform user
agents and promote the development of multi-platform assistive technologies.
Implementing standard APIs defined for a particular operating system may reduce
implementation costs for assistive technology developers who wish to
interoperate with more than one piece of software running on that operating
system.
A "device API" defines how communication may take place
with an input or output device such as a keyboard, mouse, video card, etc. A
"standard device API" is one that is considered standard for that particular
device on a given operating or windowing system.
In this document, an "input/output API" defines how
applications or devices communicate with a user agent. As used in this
document, input and output APIs include, but are not limited to, device APIs.
Input and output APIs also include more abstract communication interfaces than
those specified by device APIs. A "standard input/output API" is one that is
expected to be implemented by software running on a particular operating
system. Standard input/output APIs may vary from system to system. For example,
on desktop computers today, the standard input APIs are for
the mouse and keyboard. For touch screen devices or mobile devices, standard
input APIs may include stylus, buttons, voice, etc. The
graphical display and sound card are considered standard ouput devices for a
graphical desktop computer environment, and each has a standard
API.
- Assistive technology
- In the context of this document, an assistive technology
is a
user agent that:
- 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
rendered 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 content rendered as sound through 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 may, but is not required to, 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, or from its associated style sheets, or that are generated by the
server.
-
Captions
- Captions (sometimes called "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). See also 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, the verbs "to control"
and "to configure" share in common the idea of governance such as a user may
exercise over interface layout, user agent behavior, rendering style, and other
parameters required by this document. Generally, the difference in the terms
centers on the idea of persistence. When a user makes a change by
"controlling" a setting, that change usually does not persist beyond that user
session. On the other hand, when a user "configures" a setting, that setting
typically persists into later user sessions. Furthermore, the term "control"
typically means that the change can be made easily (such as through a keyboard
shortcut) and that the results of the change occur immediately, whereas the
term "configure" typically means that making the change requires more time and
effort (such as making the change via a series of menus leading to a dialog
box, via style sheets or scripts, etc.) and that the results of the change may
not take effect immediately (e.g., due to time spent reinitializing the system,
initiating a new session, rebooting the system). In order to be able to
configure and control the user agent, the user must be able to "read" as well
as "write" values for these parameters. Configuration settings may be stored in
a profile. The range and granularity of the
changes that can be controlled or configured by the user may depend on system
or hardware limitations.
Both configuration and control may apply at different "levels": across
Web resources (i.e., at the user agent
level, or inherited from the system), to the entirety of a Web resource, or to
components of a Web resource (e.g., on a per-element basis). In this document,
the term
global configuration is used to emphasize when a configuration
must apply across Web resources. For example, users may configure the user
agent to apply the same font family across Web resources, so that all text is displayed by default using that font
family. On the other hand, 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 having to reconfigure the user agent. 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.
User agents may allow users to choose configurations based on various
parameters, such as hardware capabilities, natural language, etc.
Note: In this document, the noun "control" means "user
interface component" or "form component".
-
Content
- In this specification, the noun "content" is used in three
ways:
- It is used to mean the document
object as a whole or in parts.
- It is used to mean 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.
- It is used in the context of the phrases non-text content and
text content.
-
Device-independence
- Device-independence refers to the ability to make use of
software with any supported input or output device.
-
Document Object,
Document Object Model
- In general usage, the term "document object" refers to the user agent's
representation of data (e.g., a document). This data generally comes from the
document
source, but may also be generated (from style sheets, scripts,
transformations, etc.), produced as a result of preferences set within the user
agent, added as the result of a repair performed automatically by the user
agent, etc. Some data that is part of the document object is routinely
rendered (e.g., in HTML, what appears between the start and end tags
of elements and the values of attributes such as "alt", "title", and
"summary"). Other parts of the document object are generally processed by the
user agent without user awareness, such as DTD-defined names of element types
and attributes, and other attribute values such as "href", "id", etc. These
guidelines require that users have access to both types of data through the
user interface.
A "document object model" is the abstraction that governs the construction
of the user agent's document object. The document object model employed by
different user agents may vary in implementation and sometimes in scope. This
specification requires that user agents implement the
APIs defined in Document Object Model
(DOM) Level 2 Specifications ([DOM2CORE] and
[DOM2STYLE]) for access to HTML,
XML, and CSS content. These DOM APIs allow authors
to access and modify the content via a scripting language (e.g., JavaScript) in
a consistent manner across different scripting languages. As a standard
interface, the DOM APIs make it easier not just for authors, but for assistive
technology developers to extract information and render it in ways most suited
to the needs of particular users.
-
Document character set
- A document character set (an concept taken from SGML) is a
sequence of abstract characters that may appear in Web content represented in a
particular format (such as HTML, XML, etc.). A document character set consists
of:
- a "repertoire", A set of abstract characters, such as the Latin letter "A",
the Cyrillic letter "I", the Chinese character meaning "water", etc.
- Code positions: A set of integer references to characters in the
repertoire.
For instance, the character set required by the HTML 4 specification [HTML4] is defined
in the Unicode specification [UNICODE]. Refer to "Character
Model for the World Wide Web" [CHARMOD] for more information
about document character sets.
-
Document source, Document source view
- In this document, the term "document source" refers to the
data that the user agent receives as the direct result of a request for a
Web resource (e.g., as the result of an
HTTP/1.1
[RFC2616] "GET", as the result of opening a local resource, etc.). A
"document source view" generally renders the document source as text written in
the markup language(s) used to build it. The document source is generally a
subset of the document
object (e.g., since the document object may include
repair content).
-
Documentation
- Documentation refers to all information
provided by the vendor about a product, including all product manuals,
installation instructions, the help system, and tutorials.
-
Element
- This document uses the term "element" both in the XML
sense (an element is a syntactic construct as described in the XML 1.0
specification
[XML], section 3) and more generally to mean a type of content (such
as video or sound) or a logical construct (such as a header or list).
-
Equivalent (for content)
- In the context of this document, an equivalency
relationship between two pieces of content
means that one piece -- the "equivalent" -- is able to serve essentially the
same function for a person with a disability (at least insofar as is feasible,
given the nature of the disability and the state of technology) as the other
piece -- the "equivalency target" -- does
for a person without any disability. For example, the text "The Full Moon"
might convey the same information as an image of a full moon when presented to
users. If the image is part of a link and understanding the image is crucial to
guessing the link target, then the equivalent must also give users an idea of
the link target. Thus, an equivalent is provided to fulfill the same function
as the equivalency target.
Equivalents include text
equivalents (e.g., text equivalents for images; text transcripts for
audio tracks; collated text transcripts for multimedia presentations and
animations) and non-text
equivalents (e.g., a prerecorded auditory description of a visual
track of a movie, or a sign language video rendition of a written text, etc.).
Please refer to the definitions of text
content and non-text
content for more information.
- Each markup language defines its own mechanisms for
specifying equivalents. For instance, in HTML 4 [HTML4] or SMIL 1.0 [SMIL], authors may
use the "alt" attribute to specify a text equivalent for some elements. In HTML
4, authors may provide equivalents (or portions of equivalents) in attribute
values (e.g., the "summary" attribute for the TABLE element), in element
content (e.g., OBJECT for external content it specifies, NOFRAMES for frame
equivalents, and NOSCRIPT for script equivalents), and in prose. Please consult
the Web Content Accessibility Guidelines 1.0 [WCAG10] and its associated
Techniques document [WCAG10-TECHS] for more
information about equivalents.
- Events and
scripting, event handler
- User agents often perform a task when an event occurs that
is due to user interaction (e.g., document loading, mouse motion or a key
press), a request from the operating system, etc. Some markup languages allow
authors to specify that a script, called an event handler, be executed when
the event occurs. Note: The combination of HTML, style sheets,
the Document Object Model (DOM) and scripting is commonly
referred to as "Dynamic HTML" or DHTML. However, as there is no W3C
specification that formally defines DHTML, this document only refers to event
handlers and scripts.
-
Explicit user request
- In several checkpoints in this document, the term "explicit user request"
is used to mean any user interaction
recognized with certainty to be for a specific purpose. For
instance, when the user selects "New viewport" in the user agent's user
interface, this is an explicit user request for a new viewport. On the other
hand, it is not an explicit request when the user activates a link and that
link has been marked up by the author to open a new viewport (since the user
may not know that a new viewport will open). Nor is it an explicit user request
even if the link text states "will open a new viewport". Some other examples of
explicit user requests include "yes" responses to prompts from the user agent,
configuration through the user agent's user interface, activation of known form
submit controls, and link activation (which should not be assumed to mean more
than "get this linked resource", even if the link text or title or role
indicates more). Some examples of behaviors that happen without explicit user
request include changes due to scripts. Note: Users make
mistakes. For example, a user may submit a form inadvertently by activating a
known form submit control. In this document, this type of mistake is still
considered an explicit user request.
- Fee
link
- For the purpose of this document, the term "fee link"
refers to a link that when activated, debits the user's electronic "wallet"
(generally, a "micropayment"). The link's role as a fee link must be identified
through markup in a manner that the user agent can
recognize. This definition of fee link excludes payment mechanisms
(e.g., some form-based credit card transactions) that cannot be recognized by
the user agent as causing payments. For more information about fee links, refer
to "Common Markup for micropayment per-fee-links"
[MICROPAYMENT].
-
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 (e.g., a link or radio button). 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.).
In this document, the term "focus" by itself encompasses both types of focus.
Where one is meant specifically in this document, it is identified.
When several viewports coexist, each may have a content and user interface
focus. At all times, only one content focus or one user
interface focus is active, called the current focus. The current focus responds
to user input and may be toggled between content focus and user interface focus
through the keyboard, pointing device, etc. Both the content and user interface
focus may be
highlighted. See also the definition of point of regard.
-
Graphical
- In this document, the term "graphical" refers to
information (text, colors, graphics, images, animations, etc.) rendered for
visual consumption.
-
Highlight
- In this document, "to highlight" means to emphasize
through the user interface. For example, user agents highlight which content is
selected or focused and which viewport is the current viewport. Graphical
highlight mechanisms include dotted boxes, underlining, and reverse video.
Synthesized speech highlight mechanisms include alterations of voice pitch and
volume.
- Input configuration
- An input configuration is the mapping of user agent
functionalities to some user
interface trigger mechanisms (e.g., menus, buttons, keyboard keys,
voice commands, etc.). The default input configuration is the mapping the user
finds after installation of the software; it must be part of the user agent
documentation (per checkpoint 10.3]). Input
configurations may be affected by author-specified bindings (e.g., through the
"accesskey" attribute of HTML 4 [HTML4]).
-
Multimedia Presentation
- For the purposes of this document, a multimedia
presentation is a
presentation that is not a visual-only presentation,
audio-only presentation, or tactile-only presentation. In a "classic"
multimedia presentation (e.g., a movie that has sound track or an animation
with accompanying audio), at least one
visual track is closely
synchronized with at least one
audio track.
-
Natural language
- Natural language is spoken, written, or signed human
language such as French, Japanese, and American Sign Language. On the Web, the
natural language of content may
be specified by markup or HTTP headers. Some examples include the
"lang" attribute in HTML 4 ([HTML4] section 8.1), the "xml:lang"
attribute in XML 1.0 ([XML], section 2.12), the
HTML 4 "hreflang" attribute for links in HTML 4
([HTML4],
section 12.1.5), the HTTP Content-Language header ([RFC2616], section 14.12) and the
Accept-Language request header ([RFC2616], section 14.4). See also
the definition of script.
-
Placeholder
- A placeholder is content generated by the user agent to
replace author-supplied content. A placeholder may be generated as the result
of a user preference (e.g., to not render images) or as
repair content (e.g., when an image
cannot be found). Placeholders can be any type of content, including text and
images. This document does not require user agents to include placeholders in
the document
object. A placeholder inserted in the document object should conform
to the Web Content Accessibility Guidelines 1.0 [WCAG10]. If a placeholder is not
part of the document object, it is part of the user interface only (and
subject, for example, to checkpoint
1.3).
-
Point of regard
- The point of regard is a position in rendered
content that the user is presumed to be viewing. The dimensions of
the point of regard may vary. For example, it may be a point (e.g., a moment in
an audio rendering or a cursor in a graphical rendering), or a range of text
(e.g., focused text), or a two-dimensional area (e.g., content rendered through
a two-dimensional graphical viewport). The point of regard is almost always
within a viewport (though the dimensions of the point of regard could exceed
those of the viewport). The point of regard may also refer to a particular
moment in time for content that changes over time (e.g., an
audio-only presentation). User agents may use the focus,
selection, or other means to designate the point of regard. A user
agent should not change the point of regard unexpectedly as this may disorient
the user.
-
Presentation
- In this document, the term presentation refers to a
collection of information, consisting of one or more
Web resources, intended to be rendered
simultaneously, and identified by a single URI. In general, a presentation has
an inherent time component (i.e., it's not just a static "Web page" (refer to
the definition of "Web page" in "Web Characterization Terminology and
Definitions Sheet" [WEBCHAR]).
-
Profile
- A profile is a named and persistent representation of user preferences that
may be used to configure a user agent. Preferences include input
configurations, style preferences, natural language preferences, etc. On
systems with distinct user accounts, profiles enable users to reconfigure
software quickly when they log on, and profiles may be shared by several users.
Platform-independent profiles are useful for those who use the same user agent
on different platforms.
-
Prompt
- In this document, "to prompt" means to require input from
the user. The user agent should allow users to
configure how they wish to be prompted. For instance, for a user
agent functionality X, configurations might include: always do X without
prompting me, never do X without prompting me, don't ever do X but tell me when
you could have done X but didn't, don't ever do X and don't tell me, etc.
- Properties, values, and
defaults
- A user agent renders a document by applying formatting
algorithms and style information to the document's elements. Formatting depends
on a number of factors, including where the document is rendered: on screen, on
paper, through loudspeakers, on a braille display, on a mobile device, etc.
Style information (e.g., fonts, colors, speech prosody, 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
- Authors encode information in markup languages, style
sheet languages, scripting languages, protocols, etc. When the information is
encoded in a manner that allows the user agent to process it with certainty,
the user agent can "recognize" the information. For instance, HTML allows
authors to specify a heading with the H1 element, so a user agent that
implements HTML can recognize that content as a heading. If the author creates
headings using a visual effect alone (e.g., by increasing the font size), then
the author has encoded the heading in a manner that does not allow the user
agent to recognize it as a heading.
Some requirements of this document depend on content roles, content
relationships, timing relationships, and other information that must be
supplied by the author. These requirements only apply
when the author has encoded that information in a manner that the user agent
can recognize. See the section on conformance for
more information about applicability.
In practice, user agents will rely heavily on information that the author
has encoded in a markup language or style sheet language. Information encoded
in a script may not be recognized by the user agent as easily. For instance, a
user agent is not expected to recognize that, when executed, a script will
calculate a factorial. The user agent will be able to recognize some
information in a script by virtue of implementing the scripting language or a
known program library (e.g., the user agent is expected to recognize when a
script will open a viewport or retrieve a resource from the Web). The
Techniques document [UAAG10-TECHS] lists some
markup known to affect accessibility that user agents can recognize.
-
Rendered content, rendered text
- Rendered content is the part of
content capable of being perceived by a user through a given
viewport (whether visual, auditory, or tactile). Some rendered content may lie
"outside" of a viewport at some times (e.g., when the user can only view a
portion of a large document through a small graphical viewport, when audio
content has already been played, etc.). By changing the viewport's position,
the user can view the remaining rendered content.
- Note: In the context of this document, "invisible content" is
content that influences graphical rendering of other content but is not
rendered itself. Similarly,
"silent content" is content that influences audio rendering of other
content but is not rendered itself. Neither invisible nor silent content is
considered rendered content.
-
Repair content, repair text
- In this document, the term "repair content" refers to
content generated by the user agent in order to correct an error condition.
"Repair text" means repair content consisting only of
text. Some error conditions that may lead to the generation of
repair content include:
- Erroneous or incomplete content (e.g., ill-formed markup, invalid markup,
missing text
equivalents, etc.);
- Missing resources for handling or rendering content (e.g., the user agent
lacks a font family to display some characters, the user agent doesn't
implement a particular scripting language, etc.);
This document does not require user agents to include repair content in the
document
object. Repair content inserted in the document object should
conform to the Web Content Accessibility Guidelines 1.0 [WCAG10]. For
more information about repair techniques for Web content and software, refer to
"Techniques for Authoring Tool Accessibility Guidelines 1.0"
[ATAG10-TECHS].
-
Script
- In this document, the term "script" almost always refers to a scripting
(programming) language used to create dynamic Web content. However, in
checkpoints referring to the written (natural) language of content, the term
"script" is used as in Unicode [UNICODE] to mean "A collection of
symbols used to represent textual information in one or more writing
systems."
- 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 through changes in speech prosody, for
example.
- Support, implement, conform
- In this document, the terms "support", "implement", and
"conform" all refer to what a developer has designed a user agent to do, but
they represent different degrees of specificity. A user agent "supports"
general classes of objects, such as "images" or "Japanese". A user agent
"implements" a specification (e.g., the PNG and SVG image format
specifications, a particular scripting language, etc.) or an
API (e.g., the DOM API) when it has been
programmed to follow all or part of a specification. A user agent "conforms to"
a specification when it implements the specification and satisfies its
conformance criteria. This document includes some explicit conformance
requirements (e.g., to a particular level of the "Web Content Accessibility
Guidelines 1.0"
[WCAG10]).
- Synchronize
- In this document, "to synchronize" refers to the
time-coordination of two or more presentation components (e.g., in a multimedia
presentation, a visual track with captions). For Web content developers, the
requirement to synchronize means to provide the data that will permit sensible
time-coordinated rendering by a user agent. For example, Web content developers
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.
-
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.
-
Text
- In this document, the term "text" used by itself refers to
a sequence of characters from a markup language's document character set. Refer to the "Character
Model for the World Wide Web " [CHARMOD] for more information
about text and characters. Note: This document makes use of
other terms that include the word "text" that have highly specialized meanings:
collated text transcript, non-text content,
text content, non-text
element, text
element, text
equivalent, and text
transcript.
-
Text content, non-text content, text
element, non-text element, text equivalent, non-text
equivalent
- In this document, the term "text element" means content that, when rendered, is understandable
in each of three modes to three reference groups:
- visually-displayed text, for users who are deaf and adept in reading
visually-displayed text;
- synthesized speech, for users who are blind and adept in use of synthesized
speech;
- braille, for users who are deaf-blind and adept at reading braille.
In these definitions, a text element is said to be "understandable" when it
fulfills its communication function to representatives of the three reference
groups. Furthermore, these definitions make assumptions such as the
availability of appropriate hardware and software, that content represents a
general mix of purposes (information, education, entertainment, commerce), that
the individuals in the groups are able to understand the natural language of
the content, that the individuals in the groups are not required to have
specialized skills (e.g., a computer science degree, etc.).
A text element may contain markup for style (e.g., font size or color),
structure (e.g., heading levels), and other semantics. However, the essential
function of the text element should be retained even if style information
happens to be lost in rendering. In this document, the term "text content"
refers to content that is composed of one or more text elements. A "non-text
element" is an element that fails to be understandable when rendered
in any of three modes to their respective reference disability
audiences. Thus, text elements have essential accessibility advantages often
associated with
text while non-text elements are those
that lack one or more such advantages.
In this document, the term "non-text content" refers to content that is
composed of one or more non-text elements. Per checkpoint 1.1 of "Web Content
Accessibility Guidelines 1.0" [WCAG10], authors must provide a
text equivalent for every author-supplied non-text element. Similarly, user
agent developers must provide a text equivalent for every non-text element
offered by the user agent to the user (see checkpoint 1.3).
Note that the terms "text element" and "non-text element" are defined by the
characteristics of their output (e.g., rendering) rather than those of their
input (e.g., information sources) or their internals (e.g., format). For
example, in principle, a text element can be generated or encoded in any
fashion as long as it has the proper output characteristics. In general, text
elements are composed of text (i.e., a
sequence of characters). Both text elements and non-text elements should be
understood as "pre-rendering" content in contrast to the "post-rendering"
content that they produce.
A "text equivalent" is a text element that, when rendered, serves
essentially the same function as some other content (i.e., an equivalency
target) does for a person without any disability. Similarly, a
"non-text equivalent" is a non-text element that, when rendered, serves
essentially the same function as the equivalency target does for a person
without any disability. Please refer also to the definition of
equivalent.
-
Text decoration
- In this document, a "text decoration" is any stylistic effect that the user
agent may apply to visually rendered text that does not affect the layout of
the document (i.e., does not require reformatting when applied or removed).
Text decoration mechanisms include underline, overline, and
strike-through.
-
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). See also the
definitions of captions
and
collated text transcripts.
- User
agent
- In this document, the term "user agent" is used in two
ways:
- Any software that retrieves and renders Web content for users. This may
include Web browsers, media players, plug-ins, and other programs -- including
assistive
technologies -- that help in retrieving and rendering Web
content.
- The subject of a
conformance claim to this document. This is the most common use of the term
in this document and is the usage in the checkpoints.
-
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.
-
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
loudspeaker, a virtual magnifying glass, etc. A viewport may contain another
viewport (e.g., nested frames). User interface controls such as prompts, menus,
alerts, etc. are not viewports.
The viewport that contains both the
current focus and the current selection is called the current
viewport. The current viewport is generally highlighted when several viewports coexist. A
user agent must provide mechanisms for accessing all content that can be
presented by each viewport (e.g., scrolling mechanisms, advance and rewind,
etc.).
- User agents may render the same content in a variety of
ways; each rendering is called a
view. For instance, a user agent may allow users to view an
entire document or just a list of the document's headers. These are two
different views of the document.
-
Voice browser
- From "Introduction and Overview of W3C Speech Interface Framework"
[VOICEBROWSER]: "A voice browser is a device (hardware and software)
that interprets voice markup languages to generate voice output, interpret
voice input, and possibly accept and produce other modalities of input and
output."
-
Web resource
- The term "Web resource" is used in this document in
accordance with Web Characterization Terminology and Definitions Sheet [WEBCHAR] to
mean anything that can be identified by a Uniform Resource Identifier
(URI) as defined in RFC 2396 [RFC2396].
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.
- [DOM2CORE]
-
"Document Object Model (DOM) Level 2 Core Specification", A. Le
Hors, P. Le Hégaret, L. Wood, G. Nicol, J. Robie, M. Champion, S. Byrne,
eds., 13 November 2000. This W3C Recommendation is
http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113
- [DOM2STYLE]
-
"Document Object Model (DOM) Level 2 Style Specification", V.
Apparao, P. Le Hégaret, C. Wilson, eds., 13 November 2000. This W3C
Recommendation is
http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113.
- [RFC2119]
- "Key words for use in
RFCs to Indicate Requirement Levels", S. Bradner, March 1997.
- [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.
- [ATAG10]
- "Authoring
Tool Accessibility Guidelines 1.0", J. Treviranus, C.
McCathieNevile, I. Jacobs, and J. Richards, eds., 3 February 2000. This W3C
Recommendation is http://www.w3.org/TR/2000/REC-ATAG10-20000203.
-
[ATAG10-TECHS]
-
"Techniques for Authoring Tool Accessibility Guidelines 1.0", J.
Treviranus, C. McCathieNevile, I. Jacobs, and J. Richards, eds., 4 May 2000.
This W3C Note is http://www.w3.org/TR/2000/NOTE-ATAG10-TECHS-20000504/.
- [CHARMOD]
- "Character
Model for the World Wide Web", M. Dürst and F. Yergeau, eds.,
29 November 1999. This W3C Working Draft is
http://www.w3.org/TR/1999/WD-charmod-19991129/
- [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.
- [HTML4]
- "HTML 4.01
Recommendation", D. Raggett, A. Le Hors, and I. Jacobs, eds., 24
December 1999. This W3C Recommendation is
http://www.w3.org/TR/1999/REC-html401-19991224.
- [MATHML]
- "Mathematical
Markup Language", P. Ion and R. Miner, eds., 7 April 1998. This W3C
Recommendation is http://www.w3.org/TR/1998/REC-MathML-19980407.
-
[MICROPAYMENT]
-
"Common Markup for micropayment per-fee-links", T. Michel, ed., 25
August 1999. This W3C Working Draft is
http://www.w3.org/TR/1999/WD-Micropayment-Markup-19990825.
- [PNG]
- "PNG
(Portable Network Graphics) Specification 1.0", T. Boutell, ed., 1
October 1996. This W3C Recommendation is http://www.w3.org/TR/REC-png.
- [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.
- [RFC2396]
- "Uniform Resource
Identifiers (URI): Generic Syntax", T. Berners-Lee, R. Fielding, L.
Masinter, August 1998.
- [RFC2616]
- "Hypertext Transfer
Protocol -- HTTP/1.1, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,
P. Leach, T. Berners-Lee, June 1999.
- [SMIL]
- "Synchronized
Multimedia Integration Language (SMIL) 1.0 Specification", P.
Hoschka, ed., 15 June 1998. This W3C Recommendation is
http://www.w3.org/TR/1998/REC-smil-19980615.
- [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/.
- [UNICODE]
- The Unicode Consortium. "The Unicode Standard, Version 3.0", Reading, MA,
Addison-Wesley Developers Press, 2000. ISBN 0-201-61633-5. Refer also to
http://www.unicode.org/unicode/standard/versions/.
-
[VOICEBROWSER]
- "Voice
Browsers: An introduction and glossary for the requirements drafts",
M. Robin, J. Larson, 23 December 1999. This document is
http://www.w3.org/TR/1999/WD-voice-intro-19991223. This document includes
references to additional W3C specifications about voice browser
technology.
- [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-TECHS]
-
"Techniques for Web Content Accessibility Guidelines 1.0", W.
Chisholm, G. Vanderheiden, and I. Jacobs, eds. This W3C Note is
http://www.w3.org/TR/1999/WAI-WEBCONTENT-TECHS-19990505.
- [WEBCHAR]
- "Web
Characterization Terminology and Definitions Sheet", B. Lavoie, H.
F. Nielsen, eds., 24 May 1999. This is a W3C Working Draft that defines some
terms to establish a common understanding about key Web concepts. This W3C
Working Draft is http://www.w3.org/1999/05/WCA-terms/01.
- [XHTML10]
- "XHTML[tm]
1.0: The Extensible HyperText Markup Language", S. Pemberton, et
al., 26 January 2000. This W3C Recommendation is
http://www.w3.org/TR/2000/REC-xhtml1-20000126.
- [XML]
- "Extensible
Markup Language (XML) 1.0", T. Bray, J. Paoli, C.M.
Sperberg-McQueen, eds., 10 February 1998. This W3C Recommendation is
http://www.w3.org/TR/1998/REC-xml-19980210.
The active participants of the User Agent Accessibility Guidelines Working
Group who authored this document were: James Allan, Denis Anson (College
Misericordia), Kitch Barnicle, Harvey Bingham, Dick Brown (Microsoft), Al
Gilman, Jon Gunderson (Chair of the Working Group, University of Illinois,
Urbana-Champaign), Eric Hansen (Educational Testing Service), Ian Jacobs (Team
Contact, W3C), Marja-Riitta Koivunen, Tim Lacy (Microsoft), Charles
McCathieNevile (W3C), Mark Novak, David Poehlman, Mickey Quenzer, Gregory
Rosmaita (Visually Impaired Computer Users Group of New York City), Madeleine
Rothberg, and Rich Schwerdtfeger.
Many thanks to the following people who have contributed through review and
past participation in the Working Group: Paul Adelson, Olivier Borius, Judy
Brewer, Bryan Campbell, Kevin Carey, Tantek Çelik, Wendy Chisholm, David
Clark, Chetz Colwell, Wilson Craig, Nir Dagan, Daniel Dardailler, B. K. Delong,
Neal Ewers, Geoff Freed, John Gardner, Larry Goldberg, Glen Gordon, John
Grotting, Markku Hakkinen, Earle Harrison, Chris Hasser, Kathy Hewitt, Philipp
Hoschka, Masayasu Ishikawa, Phill Jenkins, Earl Johnson, Jan Kärrman (for
help with html2ps),
Leonard Kasday, George Kerscher, Peter Korn, Josh Krieger, Catherine Laws, Greg
Lowney, Susan Lesch, Scott Luebking, William Loughborough, Napoleon Maou, Peter
Meijer, Karen Moses, Masafumi Nakane, Charles Oppermann, Mike Paciello, David
Pawson, Michael Pederson, Helen Petrie, Michael Pieper, Jan Richards, Hans
Riesebos, Joe Roeder, Lakespur L. Roca, Lloyd Rutledge, Liam Quinn, T.V. Raman,
Robert Savellis, Constantine Stephanidis, Jim Thatcher, Jutta Treviranus, Claus
Thogersen, Steve Tyler, Gregg Vanderheiden, Jaap van Lelieveld, Jon S. von
Tetzchner, Willie Walker, Ben Weiss, Evan Wies, Chris Wilson, Henk Wittingen,
and Tom Wlodkowski.