User Agent Accessibility Guidelines 1.0
W3C Working Draft, 14 July 2001
- This version:
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http://www.w3.org/WAI/UA/WD-UAAG10-20010714/
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- Latest version:
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http://www.w3.org/WAI/UA/UAAG10/
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- 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). Furthermore, all users, not just users with
disabilities, are expected to find conforming user agents to be more
usable.
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 document incorporates resolutions of the User Agent Accessibility
Guidelines Working Group to issues raised during the third last call of this
document, through the 13 July 2001 teleconference. The Working Group is still
resolving last call issues as of the publication of this document, and expects
to have finished last call soon.
A list of changes
to this document is available.
Publication as a Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or obsoleted
by other documents at any time. It is inappropriate to cite W3C Working Drafts
as other than "work in progress."
Please send comments about this document to the public mailing list w3c-wai-ua@w3.org; public archives are
available.
This document is part of a series of accessibility documents published by
the Web Accessibility Initiative (WAI) of the World Wide Web
Consortium (W3C). WAI
Accessibility Guidelines are produced as part of the WAI Technical Activity. The
goals of the User Agent 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, if satisfied by user agent developers, will 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 stakeholders intersect and
complement each other as follows:
- Protocol (e.g., HTTP) and content format (e.g., HTML, XML, SVG, etc.)
specifications allow communication on the Web. Format designers include
features that authors should use to create accessible content, and features
that user agents should support through an accessible user interface.
- Authors make use of the accessibility features of different format
specifications, use markup appropriately, 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 8.1 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 12.1
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. Formats generally do
not enable authors to encode all of their knowledge in a way that a user agent
can
recognize 100%. 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 2.7 and checkpoint 2.11) for cases where content does not conform to
WCAG 1.0. Furthermore, this document includes some requirements to address
certain widespread authoring practices that are discouraged because they may
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 user
agents with multimedia capabilities running in the following type of
environment (typically that of a desktop computer):
- The operating environment includes a keyboard;
- Assistive technologies may be used in the operating environment and may
communicate with the conforming user agent;
This document is not designed so that user agents on other types of
platforms (e.g., handheld devices, kiosks, etc.) will readily conform. This
document does not forbid conformance by any user agent, but some
requirements (e.g., implementation of certain APIs) are not likely to be
satisfied on environments other than the target environment. Future work by the
UAWG may address the accessibility of user agents running on
handheld devices, etc.
The target 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.
This document was designed to improve the accessibility of target user
agents for users with one or more disabilities (including visual, hearing,
physical, and cognitive) in two ways:
- 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) or
input modalities (such as mouse or voice). See the section on conformance for more information.
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, speak, 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 pointing device.
This document does not include requirements to meet all known accessibility
needs. Some known limitations of this document include the following:
- 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.,
the checkpoints of guideline 7 and
guideline 11)) but 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 rendering with groups in W3C's Voice Browser Activity.
- Output modalities. This document does not include requirements for braille
rendering. Some requirements are specific to graphical rendering and others
specific to synthesized speech rendering (speech rendering requirements are
made by checkpoint
4.12 to checkpoint
4.16). Many of the requirements of this document are generic enough to
apply to any output modality (including braille). User agents conform to this document by supporting some combination
of graphical and audio/speech rendering output; see the section on content type labels for more information.
- 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]).
- Background image interference. The requirement of checkpoint 3.1 to
allow the user to turn off rendering of background images does not extend to
multi-layered rendering.
- User control of every user interface component. This document includes some
requirements for user control of user interface components that may be changed
through content (see guideline
5). However, these requirements do not account for every user interface
component that the author may affect (e.g., the author might supply a script
that causes text to scroll in the status bar). User agents are required to
follow software usability guidelines (see checkpoint 7.3), which are also expected to include
requirements for user control over user interface behavior.
Note. It is more difficult for users to distinguish content from user
interface when both are rendered as sound in one dimension, than it is when
both are rendered visually in two dimensions. Developers of aural user agents
are therefore strongly encouraged to apply the requirements of this document to
both content and user agent components.
- Time. This document includes requirements for control of some time
parameters (including
checkpoint 2.4, checkpoint
4.4, checkpoint 4.5,
and checkpoint 4.12).
The requirements are for time parameters that the user agent recognizes and
controls. This document does not include requirements for control of time
parameters managed on the server.
- 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.
Note: The User Agent Accessibility Guidelines Working Group
may address these topics in a future version of the User Agent Accessibility
Guidelines. Even though UAAG 1.0 does not address these
topics, user agent developers are encouraged to consider them in their
designs.
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 7.3). Involving
people with disabilities in the design and testing of software will generally
improve the accessibility of the software.
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,
operating environment conventions, etc.) are already covered by the
complete set of checkpoints.
Many users without disabilities are likely to benefit from the requirements
developed to benefit users with disabilities. For example, users without
disabilities:
- 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.
- 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.
- 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 is expected to 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 twelve 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 visually rendered text" and second group of "checkpoints for
audio volume control"." Within each group, checkpoints are ordered according to
their priority, e.g., Priority 1 before Priority 2.
Within a guideline, checkpoint groupings and checkpoint order have no bearing
on conformance.
Each checkpoint definition includes the following:
- The checkpoint number.
- Informative: The checkpoint title. This title is not a
requirement, just a phrase to help readers remember an important requirement
made by the checkpoint statement.
- Normative: The priority of the
checkpoint.
- Normative: The statement or statements of the checkpoint.
These statements include one or more requirements that must be satisfied by the
user agent (i.e., the "subject of the claim) for
the purposes of conformance.
- Normative: A "content or user
agent or both" label indicating whether the requirements of the checkpoint
must be satisfied by the subject of the claim for all
content, all rendered
content, for user agent features, or for both content and user agent
features.
- Informative: A link to rationale, implementation details,
references, and more information in "Techniques for User Agent Accessibility
Guidelines 1.0" [UAAG10-TECHS].
- Normative: Content type
labels (zero or more). Content type labels are explained in the section on
conformance.
- Informative: Optional notes about the checkpoint
(beginning with the word "Note"). They notes clarify the scope
of the checkpoint through further description, examples, cross references, and
commentary. Some checkpoints in this document are more general than others, and
some may overlap in scope. Therefore, a checkpoint may be identified as a
"special case" or an "important special case" of one or more other
checkpoints.
Each checkpoint definition expresses one or more requirements. These
requirements are not technology specific. In fact, they have been designed to
be largely technology independent, in order to make sense for a variety of
existing and future technologies. "Techniques for User Agent Accessibility
Guidelines 1.0" [UAAG10-TECHS] is an important resource to help developers
understand how to "apply" the requirements to HTML, CSS, SMIL, and SVG, and
several operating environments. The User Agent Accessibility Guidelines Working
Group welcomes comments and anticipates discussion on how to apply these
requirements to new technologies in different operating environments.
Each requirement is a "minimal" requirement, which means that for
conformance, the user agent is required to satisfy no more than the stated
requirement. In many cases, however, it may be easier or less costly (or just
be better design) to implement a general feature that satisfies more than a
minimal requirement. One general solution might satisfy five checkpoints and be
easier to implement than five disconnected features. For instance, a navigable
structure view of content that allows users to query elements for their
properties is likely to benefit all users and may be used to satisfy a number
of requirements of this document.
Some requirements have a wider impact than others. For instance, the
keyboard requirements of
checkpoint 1.1 have an impact on all other requirements in the document
related to user input: any requirement that involves user input must be
satisfied through the keyboard. Because the keyboard requirements of checkpoint 1.1 have been
factored out, the other checkpoints are shorter; they are written "Allow
configuration" instead of "Allow configuration through the keyboard."
First-time readers of the document are encouraged to read the full context
provided for each checkpoint, including the guideline prose, the surrounding
checkpoints (since nearby checkpoints are generally related), notes after
checkpoints, and associated techniques (in the Techniques document
[UAAG10-TECHS]). The checklist [UAAG10-CHECKLIST] is
also a useful tool (e.g., for evaluating a user agent for conformance), but
does not provide the same contextual support.
Each checkpoint in this document is assigned a priority that indicates its
importance for users with disabilities.
- Priority 1
(P1)
- 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
(P2)
- 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
(P3)
- 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 may have to operate the user interface with
a variety of input devices (keyboard, pointing device, voice input, etc.) and
output modalities (e.g.,
graphical, speech, or braille rendering).
Though it may seem contradictory, enabling full user agent operation through
the keyboard is an important part of promoting device-independence given
today's user agents. In addition to the fact that some form of keyboard is
supported by most platforms, there are several reasons for this:
- For some users (e.g., users with blindness or physical disabilities),
operating a user agent with a pointing device may be difficult or impossible
since it requires tracking the pointing device position in a two-dimensional
visual space. Keyboard operation does not generally require as much movement
"through space".
- Some assistive technologies that support a diversity of input and output
mechanisms use keyboard APIs for communication with some
user agents; see checkpoint
6.6. People who cannot or do not use a pointing device may interact with
the user interface with the keyboard, through voice input, a head wand, touch
screen, or other device.
While this document only requires keyboard operation for conformance, it promotes device-independence by also
allowing people to claim conformance for full pointing device support or full
voice support.
As a way to promote output device independence, this guideline requires
support for text messages in the user interface because text may be rendered
visually, as synthesized speech, and as braille.
The API requirements of
guideline 6 also promote device independence by ensuring communication with
specialized software.
Checkpoints
1.1 Full keyboard access. (P1)
- Ensure that the user can operate through keyboard input alone any user
agent functionality available through the
user interface.
For both content and user agent
Techniques for checkpoint 1.1
Note: User agents may support at least two types of
keyboard access to functionalities: direct access (where user awareness of a
location "in space" is not required, as is the case with keyboard shortcuts and
navigation of user agent menus) and spatial access (where the user moves the
pointing device "in space" via the keyboard). To satisfy this checkpoint, user
agents are expected to provide a mix of both types of keyboard access. User
agents should allow direct keyboard access where possible, and this may be
redundant with spatial input techniques. Furthermore, the user agent should
satisfy this requirement by offering a combination of keyboard-operable user
interface controls (e.g., keyboard operable print menus and settings) and
direct keyboard operation of user agent functionalities (e.g., a short cut to
print the current page). As examples of functionalities, ensure that the user
can interact with enabled
elements, select content, navigate viewports, configure the user
agent, access documentation, install the user agent, operate controls of the
user interface, etc., all entirely through keyboard input. It is also possible
to claim conformance to this document for full
support through pointing device input and voice input. See the section on input modality labels.
1.2 Activate event handlers.
(P1)
- For the element with content
focus, allow the user to activate
any explicitly associated input device
event handlers through keyboard input alone.
- The user agent is not required to allow activation of event handlers
associated with a given device (e.g., the pointing device) in any order other
than what the device itself allows.
For all rendered content
Techniques for checkpoint 1.2
Note: The requirements for this checkpoint refer to
any explicitly associated input device
event handlers associated with an
element, independent of the input
modalities for which the user agent conforms. For example, suppose that an
element has an explicitly associated handler for pointing device events. Even
when the user agent only conforms for keyboard input (and does not conform for
the pointing device, for example), this checkpoint requires the user agent to
allow the user to activate that handler with the keyboard. This checkpoint is
an important special case of checkpoint 1.1. Please refer to the checkpoints of guideline 9 for more information about
focus requirements.
1.3 Provide text messages. (P1)
- 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.
For user agent features
Techniques for checkpoint 1.3
Note: For example, if the user is alerted of an event by an
audio cue, a visually-rendered text equivalent in the status bar could satisfy
this checkpoint. Per checkpoint
6.4, a text equivalent for each such message must be available through an
API. See also checkpoint 6.5 for requirements for programmatic alert of
changes to the user interface.
The checkpoints in this section require the user agent to provide access to
all content through a series of complementary mechanisms designed so that if
one fails, another will provide some access. The following preferences are
embodied in the checkpoints:
- Not all content is rendered at all times. Automatic decision by the user
agent about when and where to render conditional content is preferred, but manual
choice by the user may be necessary for access.
- Structure is preferred (both the author's specified preferences and the
user's structured access), but unstructured access may be necessary for access
to all content.
- Rendering according to format specification is preferred, but a source view
of text content may be necessary for access (e.g., because of user-side error
conditions, authoring errors, inadequate specification, or incorrect user agent
implementation). For example, the user may have to look at
URIs for information, HTML comments,
XML element names, or script data. The user agent should respect
authoring synchronization cues for content that changes over time, but also
needs to allow the user to control the time intervals when user input is
possible.
- Configuration and control of rendering are important for access.
Authors may use the
conditional content mechanisms of a specification to satisfy the
requirements of the Web Content Accessibility Guidelines 1.0 [WCAG10].
Ensuring access to
conditional content 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 movies or
images).
Checkpoints
2.1 Render by specification. (P1)
- Render
content according to format specification
(e.g., for a markup language or style sheet).
- When a rendering requirement of another specification contradicts a
requirement of the current document, the user agent may disregard the rendering
requirement of the other specification and still satisfy this checkpoint.
- Rendering requirements include format-defined interactions between author
preferences and user preferences/capabilities (e.g., when to render the
"
alt
" attribute
in HTML, the rendering order of nested OBJECT
elements in HTML,
test attributes in SMIL, and the cascade in CSS2).
For all content
Techniques for checkpoint 2.1
Note: If a conforming user agent does not render a content
type, it should allow the user to choose a way to handle that content (e.g., by
launching another application, by saving it to disk, etc.). The user agent is
not required to satisfy this checkpoint for all implemented specifications; see
the section on conformance and implementing
specifications for more information.
2.2 Provide text view. (P1)
- For text formats, provide a view of the text source. For the purposes of this document,
text formats are defined to be:
- all media objects given an Internet media type of "text" (e.g., text/plain,
text/HTML, or text/*) as defined in RFC 2046 [RFC2046],
section 4.1.
- all SGML and XML applications, regardless of Internet media type (e.g.,
HTML 4.01, XHTML 1.1, SMIL, SVG, etc.).
For all content
Techniques for checkpoint 2.2
Note: A user agent would also satisfy this checkpoint by
providing a source view for any text format, not just implemented text formats.
The user agent is not required to satisfy this checkpoint for all implemented
specifications; see the section on conformance and
implementing specifications for more information.
2.3
Render conditional content. (P1)
- Allow
configuration to provide access to each piece of unrendered
conditional content "C".
- The configuration may be a switch that, for all content, turns on or off
the access mechanisms described in the next provision.
- When a specification does not explain how to provide access to this
content, do so as follows:
- If C is a summary, title, alternative, description, or expansion of another
piece of content D, provide access through at least one of the following
mechanisms:
- (1a) render C in place of D;
- (2a) render C in addition to D;
- (3a) provide access to C by querying D. In this case, the user agent must
also alert the user, on a per-element basis, to the existence of C (so that the
user knows to query D);
- (4a) allow the user to follow a link to C from the context of D.
- Otherwise, provide access to C through at least one of the following
mechanisms:
- (1b) render a
placeholder for C, and allow the user to view the original
author-supplied content associated with each placeholder;
- (2b) provide access to C by query (e.g., allow the user to query an element
for its
attributes). In this case, the user agent must also alert the user,
on a per-element basis, to the existence of C;
- (3b) allow the user to follow a link in context to C.
- To satisfy this checkpoint, the user agent may provide access on a
per-element basis (e.g., by allowing the user to query individual elements) or
for all elements (e.g., by offering a configuration to render conditional
content all the time).
For all content
Techniques for checkpoint 2.3
Note: For instance, an HTML user agent might allow users to
query each element for access to conditional content supplied for the
"alt
", "title
", and "longdesc
"
attributes. Or, the user agent might allow configuration so that the value of
the "alt
" attribute is rendered in place of all IMG
elements (while other conditional content might be made available through
another mechanism). See
checkpoint 2.10 for additional placeholder requirements.
2.4 Allow time-independent interaction.
(P1)
- For
content where user input is only possible
within a finite time interval controlled by the user agent, allow configuration to make the time interval
"infinite". Do this by pausing automatically at the end of each time interval
where user input is possible, and resuming automatically after the user has
explicitly completed input.
- In this configuration, alert the user when the session has been paused and
which enabled
elements are time-sensitive.
- When the user pauses a real-time presentation, the user agent may discard
packets that continue to arrive during the pause.
For all rendered content
Techniques for checkpoint 2.4
Note: In this configuration, the user agent may have to
pause the presentation more than once if there is more than one opportunity for
time-sensitive input. When pausing, pause synchronized content as well (whether
rendered in the same or different viewports) per checkpoint 2.6. In SMIL 1.0
[SMIL], for
example, the "begin
", "end
", and "dur
"
attributes synchronize presentation components.
The user may explicitly complete input in many different ways (e.g., by
following a link that replaces the current time-sensitive resource with a
different resource). 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).
See also checkpoint 3.5, which involves client-driven content
refresh.
2.5 Make captions, transcripts available.
(P1)
- Allow
configuration or control so
that text
transcripts,
collated text transcripts, captions,
and auditory
descriptions are rendered at the same time as the associated audio tracks and
visual tracks.
For all content
Techniques for checkpoint 2.5
Content type labels:
Video,
Audio.
Note: This checkpoint is an important special case of checkpoint 2.1.
2.6 Respect synchronization cues.
(P1)
- Respect synchronization cues during rendering.
For all rendered content
Techniques for checkpoint 2.6
Content type labels:
Video,
Audio.
Note: This checkpoint is an important special case of checkpoint 2.1.
2.7 Repair missing content. (P2)
- Allow
configuration to generate repair
text when the user agent
recognizes that the author has failed to provide
conditional content that was required by the format
specification.
- The user agent may satisfy this checkpoint by basing the repair text on any
of the following available sources of information: URI reference, content type,
or element type.
For all content
Techniques for checkpoint 2.7
Note: Some markup languages (such as HTML 4 [HTML4] and SMIL
1.0 [SMIL]
require the author to provide conditional content for some elements (e.g., the
"alt
" attribute
on the IMG
element). Repair text based on URI reference, content
type, or element type is sufficient to satisfy the checkpoint, but may not
result in the most effective repair. Information that may be recognized as relevant to repair might not be
"near" the missing conditional content in the document object. For instance, instead of
generating repair text on a simple URI reference, the user agent might look for
helpful information near a different instance of the URI reference in the same
document object, or might retrieve useful information (e.g., a title) from the
resource designed by the URI reference.
2.8 No repair text.
(P3)
- Allow at least two
configurations for when the user agent
recognizes that
conditional content required by the format specification is present
but
empty:
For all content
Techniques for checkpoint 2.8
Note: In some authoring scenarios, empty content (e.g., a
string of zero characters) may make an appropriate text equivalent, such as when non-text
content has no other function than pure decoration, or when 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.
2.9 Render conditional
content automatically. (P3)
- Allow
configuration to render all conditional content automatically. The user
agent is not required to render all conditional content at the same time in a
single viewport.
- Provide access to this content according to format specifications or where
unspecified, by applying one of the following techniques described in checkpoint 2.3: 1a, 2a, or
1b.
For all content
Techniques for checkpoint 2.9
Note: For instance, an HTML user agent might allow
configuration so that the value of the "alt
" attribute is rendered in place of all
IMG
elements (while other conditional content might be made available
through another mechanism). The user agent may offer multiple configurations
(e.g., a first configuration to render one type of conditional content
automatically, a second to render another type, etc.).
2.10
Toggle placeholders. (P3)
- Once the user has viewed the original author-supplied content associated
with a
placeholder, allow the user to turn off the rendering of the
author-supplied content.
For all rendered content
Techniques for checkpoint 2.10
Note: For example, if the user agent substitutes the
author-supplied content for the placeholder in context, allow the user to
"toggle" between placeholder and the associated content. Or, if the user agent
renders the author-supplied content in a separate viewport, allow the user to
close that viewport. Note: See checkpoint 2.3, provision
(1b) for placeholder requirements.
2.11 Alert unsupported language.
(P3)
- Allow
configuration not to render content in unsupported natural
languages (including scripts,
i.e., writing systems).
- Indicate to the user in context that author-supplied content has not been
rendered.
- This checkpoint does not require the user agent to allow different
configurations for different natural languages.
For all content
Techniques for checkpoint 2.11
Note: For example, use a text substitute or accessible
graphical icon to indicate that content in a particular language has not been
rendered.
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 text
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.
This guideline requires the user agent to allow configuration so that, when
loading Web
resources, the user agent does not render content in a manner that
may pose accessibility problems. Requirements for interactive control of rendered content are part of guideline 4.
Checkpoints
3.1 Toggle background images.
(P1)
- Allow
configuration not to render background images.
- In this configuration, the user agent is not required to retrieve
background images from the Web.
- 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".
For all content
Techniques for checkpoint 3.1
Content type labels:
Image.
Note: See checkpoint 2.3 for information about how to provide access
to unrendered background images. When background images are not rendered, user
agents should render a solid background color instead (see checkpoint 4.3).
3.2
Toggle audio, video, animated images. (P1)
- Allow
configuration not to render audio, video, or animated images except
on explicit
user request. This configuration is required 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 (e.g., when the user activates a link).
- The user agent may satisfy this checkpoint by making video and animated
images
invisible and audio
silent, but this technique is not recommended.
- 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.
For all content
Techniques for checkpoint 3.2
Content type labels:
Animation, Video,
Audio.
Note: See checkpoint 2.3 for information about how to provide access
to unrendered audio, video, and animated images. See also checkpoint 4.5, checkpoint 4.9, and checkpoint 4.10.
3.3
Toggle animated/blinking text. (P1)
- Allow
configuration to render animated or blinking text as motionless,
unblinking text. Blinking text is text whose visual rendering alternates
between visible and invisible, any rate of change.
- In this configuration, the user must still have access to the same text
content, but the user agent may render it in a separate viewport (e.g., for
large amounts of streaming text).
- The user agent also satisfies this checkpoint by always rendering animated
or blinking text as motionless, unblinking text.
For all content
Techniques for checkpoint 3.3
Content type labels:
VisualText.
Note: Animation (a rendering effect) is different from
streaming (a delivery mechanism). Streaming content might be rendered as an
animation (e.g., an animated stock ticker) or as static text (e.g., movie
subtitles, which are rendered for a limited time, but do not give the
impression of movement). See also checkpoint 3.5. apply for blinking
and
animation effects that are caused by
mechanisms that the user agent cannot
recognize.
3.4 Toggle scripts. (P1)
- Allow
configuration not to execute any executable
content (e.g., scripts and
applets).
- In this configuration, provide an option to alert the user when executable
content is available (but has not been executed).
- The user agent is only required to alert the user to the presence of more
than zero scripts or applets (i.e., per-element alerts are not required).
For all content
Techniques for checkpoint 3.4
Note: This checkpoint does not refer to plug-ins and other programs that are not part
of content. Scripts and applets may provide very
useful functionality, not all of which causes accessibility problems.
Developers should not consider that the user's ability to turn off scripts is
an effective way to improve content accessibility; turning off scripts means
losing the benefits they offer. Instead, developers should provide users with
finer control over user agent or content behavior known to raise accessibility
barriers. The user should only have to turn off scripts as a last resort.
3.5 Toggle content refresh. (P1)
- Allow
configuration so that the user agent only refreshes content on explicit user request.
- In this configuration, alert the user of the refresh rate specified in
content, and allow the user to request fresh content manually (e.g., by
following a link or confirming a prompt).
- When the user chooses not to refresh content, the user agent may ignore
that content; buffering is not required.
- This checkpoint only applies when the user agent (not the server)
automatically initiates the request for fresh content.
For all content
Techniques for checkpoint 3.5
Note: For example, allow configuration to prompt the user
to confirm content refresh, at the rate specified by the author.
3.6 Toggle redirects. (P2)
- Allow
configuration so that a "client-side redirect" (i.e., one initiated
by the user agent, not the server) only changes
content 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 specified to occur instantaneously (i.e., after no
delay).
For all content
Techniques for checkpoint 3.6
3.7 Toggle images. (P2)
- Allow
configuration not to render images.
- The user agent may satisfy this checkpoint by making images
invisible, but this technique is not recommended.
For all content
Techniques for checkpoint 3.7
Content type labels:
Image.
Note: See checkpoint 2.3 for information about how to provide access
to unrendered images.
Providing access to content (see guideline 2) includes enabling users to configure and
control its rendering. Users with low vision may require that text
be rendered at a size larger than the size specified by the author or by the
user agent's default rendering. 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
frame assumed by the author. To make the presentation accessible to these
users, user agents rendering multimedia content (audio, video, and other animations), have to allow the user to control
the playback rate of this content, and also to stop, start, pause, fast
reverse, and fast advance it manually. User agents rendering audio have to
allow the user to control the audio volume globally and to allow the user to
control independently distinguishable audio tracks.
User agents with speech synthesis capabilities need to allow users to
control various synthesized speech rendering parameters. For instance, users
who are blind and hard of hearing may not be able to make use of high or low
frequencies; these users have to be able to configure their speech synthesizers
to use suitable frequencies.
Checkpoints for visually rendered text
4.1
Configure text size. (P1)
- Allow global
configuration and control
over the reference size of visually 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 offered by
the conventional font selection mechanism of the
operating environment. If the operating environment does not offer a
font selection mechanism, allow the user to choose any size offered by the
conventional text drawing services of the operating environment.
For all rendered content
Techniques for checkpoint 4.1
Content type labels:
VisualText.
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). For example, in HTML, this might be
paragraph text. The default reference size of rendered text may vary among user
agents. User agents may offer different mechanisms to allow control of the size
of rendered text (e.g., font size control, zoom, magnification, etc.). Refer,
for example to the Scalable Vector Graphics specification [SVG] for information
about scalable rendering.
4.2 Configure font family. (P1)
- Allow global
configuration of the font family of all visually
rendered text, with an option to override font families specified by the author
or by user agent defaults.
- Allow the user to choose from among the full range of font families offered
by the conventional font selection mechanism of the
operating environment.
- For text that cannot be rendered properly using the
user's preferred font family, the user agent may substitute an alternative font
family.
For all rendered content
Techniques for checkpoint 4.2
Content type labels:
VisualText.
Note: For example, allow the user to specify that all text is to be rendered in a particular
sans-serif font family.
4.3
Configure text colors. (P1)
- Allow global
configuration of the foreground and background color of all visually
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 offered by the
conventional color selection mechanism of the
operating environment.
For all rendered content
Techniques for checkpoint 4.3
Content type labels:
ColorText.
Note: User configuration of foreground and background
colors may inadvertently lead to the inability to distinguish ordinary text
from selected text, focused text, etc. See checkpoint 10.3 for more information about highlight
styles.
Checkpoints for multimedia presentations and other
presentations that change continuously over time
4.4 Slow multimedia. (P1)
- Allow the user to slow the presentation rate of audio and animations (including video and animated
images).
- 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 and
animations whose
recognized role is to create a purely stylistic effect.
For all rendered content
Techniques for checkpoint 4.4
Content type labels:
Animation, Audio.
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 checkpoint 2.6 and checkpoint 4.7.
4.5 Start, stop, pause, advance
multimedia. (P1)
- Allow the user to stop, pause, resume, fast advance, and fast reverse audio
and
animations (including video and animated
images) that last three or more seconds at their default playback rate.
- The user agent is not required to satisfy this checkpoint for audio and
animations whose
recognized role is to create a purely stylistic effect.
- The user agent is not required to play synchronized audio during fast
advance or reverse of animations (though doing so may help orient the
user).
- The user agent is not required to play animations during fast advance and
fast reverse.
- When the user pauses a real-time audio or animation, the user agent may
discard packets that continue to arrive during the pause.
For all rendered content
Techniques for checkpoint 4.5
Content type labels:
Animation, Audio.
Note: See
checkpoint 4.4 for more information about the exception for purely
stylistic effects. This checkpoint applies to content that is either rendered
automatically or on request from the user. Respect synchronization cues per checkpoint 2.6.
4.6 Position captions. (P1)
- For graphical
viewports, allow the user to position captions
with respect to synchronized visual
tracks as follows:
- if the user agent satisfies this checkpoint by using a markup language or
style sheet language to provide configuration or control, then the user agent
must allow the user to choose from among at least the range of positions
enabled by the format
- otherwise the user agent must allow both non-overlapping and overlapping
positions (e.g., by rendering captions in a separate
viewport that may be positioned on top of the visual track).
- In either case, the user agent must allow the user to override the author's specified position.
- The user agent is not required to change the layout of other content (i.e.,
reflow) after the user has changed the position of captions.
- The user agent is not required to make the captions background transparent
when those captions are rendered above a related video track.
For all rendered content
Techniques for checkpoint 4.6
4.7 Slow other multimedia. (P2)
- Allow the user to slow the presentation rate of audio and animations (including video and animated
images) not covered by
checkpoint 4.4.
- The same speed percentage requirements of checkpoint 4.4 apply.
For all rendered content
Techniques for checkpoint 4.7
Content type labels:
Animation, Audio.
Note: User agents automatically satisfy this checkpoint if
they satisfy checkpoint 4.4
for all audio and animations.
4.8 Control other multimedia.
(P2)
- Allow the user to stop, pause, resume, fast advance, and fast reverse audio
and
animations (including video and animated
images) not covered by
checkpoint 4.5.
For all rendered content
Techniques for checkpoint 4.8
Content type labels:
Animation, Audio.
Note: User agents automatically satisfy this checkpoint if
they satisfy checkpoint
4.5 for all audio and animations.
Checkpoints for audio volume control
4.9 Global volume control. (P1)
- Allow global
configuration and control of
the volume of all audio, with an option to
override audio volumes specified by the author or user agent
defaults.
- Allow the user to choose zero volume (i.e.,
silent).
For all rendered content
Techniques for checkpoint 4.9
Content type labels:
Audio.
Note: User agents should allow configuration and control of
volume through available
operating environment controls.
4.10 Independent volume control.
(P1)
- Allow independent control of
the volumes of
audio sources synchronized to play
simultaneously.
- The user agent is not required to satisfy this checkpoint for audio whose
recognized role is to create a purely stylistic
effect.
- The user control required by this checkpoint includes the ability to override author-specified volumes for the
relevant sources of audio.
For all rendered content
Techniques for checkpoint 4.10
Content type labels:
Audio.
Note: See
checkpoint 4.4 for more information about the exception for purely
stylistic effects. The user agent should satisfy this checkpoint by allowing
the user to control independently the volumes of all
audio sources (e.g., by implementing a general audio mixer type of
functionality). See also
checkpoint 4.13.
4.11
Control other volume. (P2)
- Allow independent control of
the volumes of
audio sources synchronized to play
simultaneously that are not covered by checkpoint
4.10.
For all rendered content
Techniques for checkpoint 4.11
Content type labels:
Audio.
Note: User agents automatically satisfy this checkpoint if
they satisfy
checkpoint 4.10 for all audio.
Checkpoints for synthesized speech rendering
4.12 Configure synthesized speech rate.
(P1)
- Allow
configuration and control of
the synthesized speech rate, according to the full range offered by the speech
synthesizer.
For all rendered content
Techniques for checkpoint 4.12
Content type labels:
Speech.
Note: The range of synthesized speech rates offered by the
speech synthesizer may depend on natural language.
4.13 Configure synthesized speech volume.
(P1)
- Allow
control of the synthesized speech volume,
independent of other sources of audio.
- The user control required by this checkpoint includes the ability to override author-specified synthesized speech
volume.
For all rendered content
Techniques for checkpoint 4.13
Content type labels:
Speech.
Note: See also checkpoint 4.10.
4.14 Configure
synthesized speech characteristics. (P1)
- Allow
configuration of synthesized speech characteristics according to the
full range of values offered by the speech synthesizer.
For all content
Techniques for checkpoint 4.14
Note: Some speech synthesizers allow users to choose values
for synthesized speech characteristics at a higher abstraction layer, i.e., by
choosing from present options that group several characteristics. Some typical
options one might encounter include: "adult male voice", "female child voice",
"robot voice", "pitch", "stress", etc. Ranges for values may vary among speech
synthesizers.
4.15 Specific synthesized speech characteristics. (P2)
- Allow
configuration of the following synthesized speech characteristics:
pitch, pitch range, stress, richness.
- Pitch refers to the average frequency of the speaking voice.
- Pitch range specifies a variation in average frequency.
- Stress refers to the height of "local peaks" in the intonation contour of
the voice.
- Richness refers to the richness or brightness of the voice.
For all content
Techniques for checkpoint 4.15
Note: This checkpoint is more specific than checkpoint
4.14: it requires support for the voice characteristics listed. Definitions
for these characteristics are based on descriptions in section 19 of the
Cascading Style Sheets Level 2 Recommendation [CSS2]; please refer to that
specification for additional
informative descriptions. Some speech synthesizers allow users to
choose values for synthesized speech characteristics at a higher abstraction
layer, i.e., by choosing from present options distinguished by "gender", "age",
"accent", etc. Ranges of values may vary among speech synthesizers.
Content type labels:
Speech.
4.16 Configure synthesized speech features.
(P2)
- Provide support for
user-defined extensions to the synthesized speech dictionary, as well as the
following functionalities:
- spell-out: spell text one character at a time or according to
language-dependent pronunciation rules;
- speak-numeral: speak a numeral as individual digits or as a full number;
and
- speak-punctuation: speak punctuation literally or render as natural
pauses.
For all content
Techniques for checkpoint 4.16
Note: Definitions for the functionalities listed are based
on descriptions in section 19 of the Cascading Style Sheets Level 2
Recommendation
[CSS2]; please refer to that specification for additional informative descriptions.
Checkpoints related to style sheets
4.17
Choose style sheets. (P1)
- 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.
For both content and user agent
Techniques for checkpoint 4.17
Note: By definition, the user agent's default style sheet is always
present, but may be overridden by author or user styles. Developers should not
consider that the user's ability to turn off author and user style sheets is an
effective way to improve content accessibility; turning off style sheet support
means losing the many benefits they offer. Instead, developers should provide
users with finer control over user agent or content behavior known to raise
accessibility barriers. The user should only have to turn off author and user
style sheets as a last resort.
Control of viewport
behavior is important to accessibility. For people with visual disabilities or
certain types of learning disabilities, it is important that the point of
regard – what the user is presumed to be viewing –
remain as stable as possible. Unexpected changes may cause users to lose track
of how many viewports
are open, which viewport has the current
focus, etc. This guideline includes requirements for control of
opening and closing viewports, the relative position of graphical viewports,
changes to focus, and inadvertent form submissions and micropayments.
Checkpoints
5.1 No automatic content focus change.
(P2)
- Allow
configuration so that if a viewport
opens without explicit
user request, its content
focus does not automatically become the
current focus.
- Configuration is preferred, but is not required if the content focus can
only ever be moved on explicit
user request.
For both content and user agent
Techniques for checkpoint 5.1
5.2 Keep viewport on top. (P2)
- For graphical user interfaces, allow
configuration so that the viewport with the
current focus remains "on top" of all
other viewports with which it overlaps.
For both content and user agent
Techniques for checkpoint 5.2
5.3 Manual viewport open only. (P2)
- Allow
configuration so that viewports only open 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.
- Configuration is preferred, but is not required if viewports can only ever
open on explicit
user request.
- 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.
For both content and user agent
Techniques for checkpoint 5.3
Note: See also checkpoint 5.1 (for control over changes of focus when a
viewport opens) and checkpoint 6.5
(for programmatic alert of changes to the user interface).
5.4 Selection and focus in viewport.
(P2)
- Ensure that when a viewport's selection
or content
focus changes, it is at least partially in the viewport after the change.
For both content and user agent
Techniques for checkpoint 5.4
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.
5.5 Confirm form submission. (P2)
- Allow
configuration to prompt the
user to confirm (or cancel) any form submission.
- Configuration is preferred, but it not required if forms can only ever be
submitted on explicit
user request.
For all rendered content
Techniques for checkpoint 5.5
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" or "change" event occurs.
5.6 Confirm fee links. (P2)
- Allow
configuration to prompt the
user to confirm (or cancel) any payment that results from activation of a fee
link.
- Configuration is preferred, but is not required if fee links can only ever
be activated on explicit
user request.
For all rendered content
Techniques for checkpoint 5.6
5.7
Manual viewport close only. (P3)
- Allow
configuration to prompt the
user to confirm (or cancel) closing any viewport that starts to close without
explicit
user request.
For both content and user agent
Techniques for checkpoint 5.7
This guideline addresses interoperability between a conforming user agent
and other software, in particular assistive technologies. The checkpoints of this
guideline require implementation of application programming interfaces (APIs) for communication. There are three types
of requirements in this guideline:
- Requirements for what information must be communicated through an
API.
- Requirements for which APIs or types of
APIs must be used to communicate this information.
- Requirements for additional characteristics of these
APIs.
Note: The User Agent Accessibility Guidelines Working Group
believes that, in order to promote interoperability between a conforming user
agent and more than one assistive technology, it is more important to
implement conventional APIs than custom
APIs, even though custom APIs may superior access.
When conventional APIs do not allow users to satisfy the requirements of these
checkpoints, however, developers may implement alternative APIs in order to
conform to this document.
Checkpoints
6.1 DOM read access. (P1)
- 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:
- the Core module for HTML;
- the Core and XML modules for XML.
For all content
Techniques for checkpoint 6.1
Note: Please refer to the "Document Object Model (DOM)
Level 2 Core Specification" [DOM2CORE] for information about
HTML and XML versions covered.
6.2 DOM write access. (P1)
- 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:
- the Core module for HTML;
- the Core and XML modules for XML.
For all content
Techniques for checkpoint 6.2
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.
6.3 Programmatic access to other
content. (P1)
- For markup languages other than HTML and
XML, provide programmatic read access to
content.
- Provide programmatic write access for those parts of content that the user
can modify through the user interface. To satisfy these requirements, implement
at least one API that is either
- defined by a W3C Recommendation, or
- a publicly documented API designed to enable interoperability with
assistive technologies.
- If no such API is available, or if available APIs do not enable the user
agent to satisfy the requirements, implement at least one publicly documented
API to satisfy the requirements, and follow operating environment
conventions for the use of input and output
APIs.
- An API is considered available if the specification of the API is published
(e.g., as a W3C Recommendation) in time for integration into a user agent's
development cycle.
For all content
Techniques for checkpoint 6.3
Note: This checkpoint addresses content not covered by
checkpoints checkpoint 6.1
and checkpoint 6.2.
6.4 Programmatic operation. (P1)
- Provide programmatic read access to user
agent user interface controls.
- Provide programmatic write access for those controls that the user can
modify through the user interface. For security reasons, user agents are not
required to allow instructions in content to
modify user agent user interface controls.
- To satisfy these requirements, implement at least one
API that is either
- defined by a W3C Recommendation, or
- a publicly documented API designed to enable interoperability with
assistive technologies.
- If no such API is available, or if available APIs do not enable the user
agent to satisfy the requirements, implement at least one publicly documented
API that allows programmatic operation of all of the functionalities that are
available through the user agent user interface, and follow operating
environment
conventions for the use of input and output
APIs.
- An API is considered available if the specification of the API is published
(e.g., as a W3C Recommendation) in time for integration into a user agent's
development cycle.
For user agent features
Techniques for checkpoint 6.4
Note: APIs used to satisfy the requirements of this
checkpoint may be platform-independent APIs such as the W3C
DOM, conventional APIs for a particular operating environment, conventional
APIs for programming languages, plug-ins,
virtual machine environments, etc. User agent developers are encouraged to
implement APIs that allow assistive technologies to interoperate with multiple
types of software in a given operating environment (user agents, word
processors, spreadsheet programs, etc.), as this reuse will benefit users and
assistive technology developers. User agents should always follow operating
environment conventions for the use of input and output APIs.
6.5 Programmatic alert of changes. (P1)
- Provide programmatic alert of changes to
content, user
interface controls,
selection, content
focus, and user
interface focus.
- To satisfy these requirements, implement at least one
API that is either
- defined by a W3C Recommendation, or
- a publicly documented API designed to enable interoperability with
assistive technologies.
- If no such API is available, or if available APIs do not enable the user
agent to satisfy the requirements, implement at least one publicly documented
API to satisfy the requirements, and follow operating environment
conventions for the use of input and output
APIs.
- This checkpoint does not require alert to rendering changes due to content (e.g., an animation effect), just
changes to the content itself.
For both content and user agent
Techniques for checkpoint 6.5
Note: For instance, when user interaction in one frame
causes automatic changes to content in another, provide a programmatic alert.
An API is considered available if the specification of the API is published
(e.g., as a W3C Recommendation) in time for integration into a user agent's
development cycle.
6.6 Conventional keyboard APIs. (P1)
- Follow
operating environment conventions when implementing
APIs for the keyboard.
- If such APIs for the keyboard do not exist, implement
publicly documented APIs for the keyboard.
For user agent features
Techniques for checkpoint 6.6
Note: An operating environment may define more than one
conventional API for the keyboard. For instance, for Japanese and Chinese,
input may be processed in two stages, with an API for each.
6.7 API character encodings. (P1)
- For an API implemented to satisfy requirements of this document, support
the character
encodings required for that API.
For both content and user agent
Techniques for checkpoint 6.7
Note: Support for character encodings is important so that
text is not "broken" when communicated to assistive technologies. For example,
the DOM Level 2 Core Specification [DOM2CORE], section 1.1.5
requires that the DOMString
type be encoded using UTF-16. This
checkpoint is an important special case of the other API
requirements of this document.
6.8 DOM CSS access. (P2)
- 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.
- For the purposes of satisfying this checkpoint, Cascading Style Sheets
(CSS) are defined by either CSS Level 1
[CSS1] or CSS Level 2 [CSS2].
For all content
Techniques for checkpoint 6.8
Note: Please refer to the "Document Object Model (DOM)
Level 2 Style Specification" [DOM2STYLE] for information
about CSS versions covered.
6.9 Timely access. (P2)
- Ensure that programmatic exchanges proceed in a timely manner.
For both content and user agent
Techniques for checkpoint 6.9
Note: For example, the programmatic exchange of information
required by other checkpoints in this document should 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. Timely exchange is
also important for the proper synchronization of alternative renderings. The
techniques for this checkpoint explain how developers can reduce communication
delays. This will help ensure that assistive technologies have timely access to
the document
object model and other information that is important for providing
access.
Part of user agent accessibility involves following the conventions of the
user's operating environment. This includes:
Following
operating environment 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
7.1 Focus and selection conventions.
(P1)
- Follow
operating environment conventions that benefit accessibility when implementing the
selection, content
focus, and user
interface focus.
For user agent features
Techniques for checkpoint 7.1
Note: This checkpoint is an important special case of checkpoint 7.3. See also checkpoint 9.1 and checkpoint 9.2.
7.2 Respect input configuration conventions. (P1)
- Ensure that default input
configurations do not interfere with
operating environment accessibility conventions (e.g., for keyboard
accessibility).
For user agent features
Techniques for checkpoint 7.2
Note: Information about operating environment accessibility
conventions is available in the Techniques document
[UAAG10-TECHS].
See also checkpoint 11.5.
7.3 Operating environment conventions.
(P2)
- Follow
operating environment conventions that benefit accessibility. In
particular, follow conventions that benefit accessibility for
user interface design, keyboard
configuration, product installation, and
documentation.
- For the purposes of this checkpoint, an operating environment convention
that benefits accessibility is either
- one identified as such in operating environment design or accessibility
guidelines, or
- one that allows the author to satisfy any requirement of the "Web Content
Accessibility Guidelines 1.0" [WCAG10] or of the current
document.
For user agent features
Techniques for checkpoint 7.3
Note: Some of these conventions (e.g., sticky keys, mouse
keys, show sounds, etc.) are discussed in the Techniques document
[UAAG10-TECHS].
7.4 Input configuration indications.
(P2)
- Follow
operating environment conventions to indicate the input
configuration.
For user agent features
Techniques for checkpoint 7.4
Note: For example, in some operating environments, when a
functionality may be triggered through a menu and through the keyboard, the
developer may design the menu entry so that the character of the activating key
is also shown. This checkpoint is an important special case of checkpoint 7.3. See also checkpoint
11.5.
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 6).
While developers should implement the accessibility features of any
specification (checkpoint 8.1), this document recommends conformance to W3C
Recommendations in particular (checkpoint 8.2) 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
8.1 Implement accessibility features.
(P1)
- Implement the accessibility features of specifications (markup languages,
style sheet languages, metadata languages, graphics formats, etc.). For the
purposes of this checkpoint, an accessibility feature is either
- one identified as such, or
- one that allows the author to satisfy any requirement of the "Web Content
Accessibility Guidelines 1.0" [WCAG10].
For all content
Techniques for checkpoint 8.1
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. The user agent is not
required to satisfy this checkpoint for all implemented specifications; see the
section on conformance and implementing
specifications for more information.
8.2 Conform to specifications. (P2)
- Use and conform to
either
- W3C Recommendations when they are available and appropriate for a task,
or
- non-W3C specifications that enable the creation of content that conforms at
level A or better to the Web Content Accessibility Guidelines 1.0 [WCAG10].
- When a requirement of another specification contradicts a requirement of
the current document, the user agent may disregard the requirement of the other
specification and still satisfy this checkpoint.
- A specification is considered available if it is published (e.g., as a W3C
Recommendation) in time for integration into a user agent's development
cycle.
For all content
Techniques for checkpoint 8.2
Note: For instance, for markup, the user agent may conform to HTML 4 [HTML4], XHTML 1.0
[XHTML10], or XML 1.0 [XML]. For style sheets, the user
agent may conform to CSS ([CSS1], [CSS2]). For mathematics, the user
agent may conform to MathML 2.0 [MATHML20]. For synchronized
multimedia, the user agent may conform to SMIL 1.0 [SMIL]. The user
agent is not required to satisfy this checkpoint for all implemented
specifications; see the section on conformance and
implementing specifications for more information.
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 enabled element), and review the surrounding
context (to orient themselves). Providing a variety of navigation and search
mechanisms helps users with disabilities (and all users) access content more
efficiently. Navigation and searching are 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 enabled 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 (e.g., to a particular link or paragraph) 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." Direct navigation may be possible with the pointing device or
the keyboard (e.g., keyboard shortcuts).
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,
enabled elements, navigation mechanisms, containers, etc. For information about
programmatic access to document structure, see guideline 6.
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
9.1 Provide content focus. (P1)
- Provide at least one content
focus for each viewport
(including frames) where enabled elements are part of the rendered
content.
- Allow the user to make the content focus of each viewport the
current focus.
For all rendered content
Techniques for checkpoint 9.1
Note: For example, when two frames of a frameset contain
enabled elements, allow the user to make the
content focus of either frame the current focus. Note that viewports
"owned" by
plug-ins that are part of a conformance
claim are also covered by this checkpoint.
9.2 Provide user interface focus. (P1)
- Provide a user
interface focus.
For user agent features
Techniques for checkpoint 9.2
9.3 Move content focus. (P1)
- Allow the user to move the content
focus to any enabled
element in the
viewport.
- If the author has not specified a navigation order, allow at least forward
sequential navigation to each element, in document order.
- The user agent may also include disabled elements in the navigation order.
For all rendered content
Techniques for checkpoint 9.3
Note: In addition to forward sequential navigation, the
user agent should also allow reverse sequential navigation. This checkpoint is
an important special case of
checkpoint 9.9.
9.4 Restore history. (P1)
- For user agents that implement a viewport history mechanism, for each state
in a viewport's browsing history, maintain information about the point of
regard, content
focus, and
selection.
- When the user returns to any state in the viewport history, restore the
saved values for all of these state variables.
For both content and user agent
Techniques for checkpoint 9.4
Note: For example, when the user uses the "back"
functionality, restore the four state variables.
9.5 No events on focus change.
(P2)
- Allow
configuration so that moving the
content focus to or from an enabled element does not automatically activate any explicitly associated
event handlers.
For all rendered content
Techniques for checkpoint 9.5
Note: For instance, in this configuration for an HTML
document, do not activate any handlers for the 'onfocus
',
'onblur
', or 'onchange
' attributes. In this
configuration, user agents should still apply any stylistic changes (e.g., highlighting) that may occur when there is a
change in content
focus.
9.6 Show event handlers. (P2)
- For the element with content
focus, make available the list of input device
event handlers explicitly associated with
the element.
For all content
Techniques for checkpoint 9.6
Note: For example, allow the user to query the element with
content focus for the list of input device event handlers, or add them directly
to the serial navigation order described in checkpoint 9.3. See checkpoint 1.2 for
information about activation of event handlers associated with the element with
focus.
9.7 Move content focus optimally. (P2)
- Allow the user to move the content
focus to any enabled
element in the
viewport.
- If the author has not specified a navigation order, allow at least forward
and reverse sequential navigation to each element, in document order.
- The user agent must not include disabled elements in the navigation order.
For all rendered content
Techniques for checkpoint 9.7
Note: This checkpoint is a special case of checkpoint 9.3.
9.8 Text search.
(P2)
- Allow the user to search within rendered text 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 do both of the following:
- move the viewport so that the matched text content is within it, and
- 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, when the search reaches the end of
content, and prior to any wrapping. A wrapping search is one that restarts
automatically at the beginning of content once the end of content has been
reached.
- Provide a case-insensitive search option for text in
scripts (i.e., writing systems) where case is significant.
For all rendered content
Techniques for checkpoint 9.8
Note: If the user has not indicated a start position for
the search, the search should start from the beginning of content. Per checkpoint 7.3, use
operating environments conventions for indicating the result of a
search (e.g., selection
or content
focus).
9.9 Structured navigation. (P2)
- Allow the user to navigate efficiently to and among important structural
elements.
- Allow forward and backward sequential navigation to important structural
elements.
For all rendered content
Techniques for checkpoint 9.9
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.
9.10
Configure important elements. (P3)
- Allow
configuration and control of
the set of important elements required by checkpoint 9.9 and checkpoint 10.5.
- Allow the user to include and exclude element types in the set of
elements.
For all content
Techniques for checkpoint 9.10
Note: For example, allow the user to navigate only
paragraphs, or only headings and paragraphs, or to suppress and restore
navigation bars, to navigate within and among tables and table cells, etc.
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 through the user interface
(visually, as audio, or as braille) include:
- information about the current state of the user's interaction with content:
where the viewport is in content (shown, for example, through proportional
scroll bars), which viewport has the
current focus, where the user has selected content, a history
mechanism, the title of the current document or frame, etc. These clues need to
be available to the user in a device-independent manner;
- information about specific 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.
- information about the structure of content. For instance, a navigable
outline view can accelerate access to content while preserving context.
Orientation mechanisms such as these are especially important to users who
view content serially, (e.g., when rendered as synthesized 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 need to 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.
This guideline also includes requirements to allow the user to control some
user agent behavior (form submission and activation of fee links) that, if
carried out automatically, might go unnoticed by some users (e.g., users with
blindness) or might disorient others (e.g., some users with a cognitive
disability).
Checkpoints
10.1 Table orientation. (P1)
- Make available to the user the purpose of each table (e.g., as expressed in
a summary or table caption) and the relationships among the table cells and
headers.
For all rendered content
Techniques for checkpoint 10.1
Note: This checkpoint refers only to table purpose and
cell/header relationship information that the user agent can recognize. 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. This checkpoint is an important special case of checkpoint 2.1.
10.2 Highlight selection and content focus.
(P1)
- Provide a mechanism for
highlighting the selection
and content
focus of each viewport.
- The highlight mechanism must not rely on color alone.
- Allow global
configuration of selection and focus highlight styles.
- 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 offered by the conventional color and text
decoration selection mechanisms of the operating environment.
For all rendered content
Techniques for checkpoint 10.2
Note: Examples of highlight mechanisms include foreground
and background color variations, underlining, distinctive synthesized speech
prosody, 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
7.1.
10.3 Distinct default highlight
styles. (P1)
- Ensure that all of the default highlight
styles for the
selection, content
focus, enabled
elements, recently visited links, and fee
links
- do not rely on color alone, and
- differ from each other, and not by color alone.
- This checkpoint not apply to those highlight styles inherited from the
operating environment as default values, as long as the user can change the
styles in the operating environment.
For all rendered content
Techniques for checkpoint 10.3
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, enabled 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.
10.4 Highlight special elements. (P2)
- Provide a mechanism for
highlighting all enabled
elements, recently visited links, and fee
links.
- 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 offered by the conventional color, font, and
text decoration selection mechanisms of the
operating environment.
- For an image map, the user agent must highlight the image map as a whole
and should allow configuration to highlight each enabled region.
For all rendered content
Techniques for checkpoint 10.4
Note: Examples of highlight mechanisms include foreground
and background color variations, font variations, underlining, distinctive
synthesized speech prosody, rectangular boxes, etc.
10.5
Outline view. (P2)
- 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.).
- What constitutes a label is defined by each markup language specification.
A label is not required to be text
only.
For all content
Techniques for checkpoint 10.5
Note: This checkpoint is meant to provide the user with a
simplified view of content (e.g, a table of contents). 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. 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 9.9. By making the
outline view navigable, it is possible to satisfy this checkpoint and checkpoint 9.9 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 9.10.
10.6 Provide link information. (P3)
- To help the user decide whether to traverse a link, make available the
following information about it:
- link element content,
- link title,
- whether the link is internal to the resource (e.g., the link is to a target
in the same Web page),
- 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.
For all rendered content
Techniques for checkpoint 10.6
Checkpoints for the user interface
10.7 Highlight current viewport.
(P1)
- Provide a mechanism for
highlighting the viewport with the
current focus (including any frame that takes current focus).
- For graphical viewports, the default highlight mechanism must not rely on
color alone.
- This default color requirement does not apply if the highlight mechanism is
inherited from the operating environment as the default and the user can change
it in the operating environment.
For user agent features
Techniques for checkpoint 10.7
Note: This checkpoint is an important special case of checkpoint 1.1. See also
to checkpoint
checkpoint 7.1.
10.8 Indicate rendering progress. (P3)
- Indicate the
viewport's position relative to 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.).
- 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.
- For two-dimensional renderings, relative position includes both vertical
and horizontal positions.
- 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 all content
Techniques for checkpoint 10.8
Web users have a wide range of capabilities and need to be able to configure the user agent according to their
preferences for styles, graphical user interface configuration, keyboard
configuration, etc. Most of the checkpoints in this guideline pertain to the
input configuration: how user agent behavior is controlled through keyboard
input, pointing device input, and voice input.
Checkpoints
11.1 Current user bindings. (P1)
- Provide information to the user about current user preferences for input
configurations.
- 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).
For user agent features
Techniques for checkpoint 11.1
11.2 Current author bindings.
(P2)
- Provide a centralized view of the current author-specified input
configuration bindings.
- The user agent may satisfy this checkpoint by providing different views for
different input modalities (keyboard, pointing device, voice, etc.).
For all content
Techniques for checkpoint 11.2
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.
11.3 Override bindings. (P2)
- Allow the user to override
any binding that is part of the user agent default input
configuration.
- The user agent is not required to allow the user to override conventional
bindings for the
operating environment (e.g., for access to help).
- The override requirement only applies to bindings for the same input
modality (e.g., the user must be able to override a keyboard binding with
another keyboard binding).
For user agent features
Techniques for checkpoint 11.3
Note: See also checkpoint 11.5, checkpoint 11.7, and checkpoint 12.3.
11.4 Single key access. (P2)
- Allow the user to override
any binding in the user agent default keyboard configuration with a binding to
either a key plus modifier keys or to a single-key. In this checkpoint, "key"
refers to a physical key of the keyboard (rather than, say, a character of the
document character set).
- For each functionality in the set required by checkpoint 11.5, allow the
user to configure
a single-key binding (i.e., one key press performs the task, with zero modifier
keys).
- If the number of physical keys on the keyboard is less than the number of
functionalities required by checkpoint 11.5, allow single-key bindings for as many of
those functionalities as possible.
- The single-key binding requirements may be satisfied with a "single-key
mode" (i.e., a mode where the current bindings are replaced by a set of
single-key bindings).
- The user agent is not required to allow the user to
override conventional bindings for the
operating environment (e.g., for access to help).
- This checkpoint does not require single physical key bindings for character
input, only for the activation of user agent functionalities.
For user agent features
Techniques for checkpoint 11.4
Note: Because single-key access is so important to some
users with physical disabilities, user agents should ensure that (1) most keys
of the physical keyboard may be configured for single-key bindings, and (2)
most functionalities of the user agent may be configured for single-key
bindings. For information about access to user agent functionality through a
keyboard API, see checkpoint
6.6.
11.5
Default binding requirements. (P2)
- Ensure that the user agent default input configuration includes bindings for the
following functionalities required by other checkpoints in this document:
- move focus to next enabled
element, and move focus to previous enabled element;
- activate focused link;
- search for text;
- search again for same text;
- increase size of rendered
text, and decrease size of rendered text;
- increase global volume, and decrease global volume;
- stop, pause, resume, fast advance, and fast reverse selected audio and animations (including video and animated
images).
- If the user agent supports
the following functionalities, the default input configuration must also
include bindings for them:
- next history state (forward), and previous history state (back);
- enter URI for new resource;
- add to favorites (i.e., bookmarked resources);
- view favorites;
- stop loading resource;
- reload resource;
- refresh rendering;
- forward one viewport, and back one viewport;
- next line, and previous line.
For user agent features
Techniques for checkpoint 11.5
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 11.3.
11.6 User profiles. (P2)
- For the configuration requirements of this document, allow the user to save
user preferences in at least one user
profile.
- Allow the user to choose from among available default profiles, profiles
created by the same user, and no profile (i.e., the user agent default
settings).
For user agent features
Techniques for checkpoint 11.6
11.7 Configure tool bars. (P3)
- 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.
For user agent features
Techniques for checkpoint 11.7
Note: This checkpoint is a special case of checkpoint 11.3.
Documentation of the user interface is important, as is documentation of the
user agent's underlying functionalities. While intuitive user interface design
is valuable to many users, some users may still not be able to understand or be
able to operate the native user interface without thorough documentation (e.g.,
a user with blindness may not find a graphical user interface intuitive without
supporting documentation).
There are three types of requirements in this guideline:
- accessibility of the documentation (checkpoint 12.1);
- minimal requirements of what must be documented (checkpoint 12.2, checkpoint 12.3, and checkpoint 12.4).
Documentation should include much more to
explain how to install, get help for, use, or configure the user agent;
- organization of the documentation (checkpoint 12.5).
Refer to checkpoint 7.3
for information about following system conventions for documentation.
Checkpoints
12.1 Accessible documentation. (P1)
- Ensure that at least one version of the user agent
documentation conforms to at least Level
Double-A of the Web Content Accessibility Guidelines 1.0
[WCAG10].
For user agent features
Techniques for checkpoint 12.1
12.2 Document accessibility features.
(P1)
-
Document all user agent features that benefit accessibility.
- For the purposes of this checkpoint, a user agent feature that benefits
accessibility is one implemented to satisfy the requirements of this document
(including the requirements of checkpoints 8.1 and 7.3).
- The user agent may satisfy this checkpoint either by
- providing a centralized view of the accessibility features, or
- integrating accessibility features into the rest of the documentation.
For user agent features
Techniques for checkpoint 12.2
Note: The help system should include discussion of user
agent features that benefit accessibility. The user agent should satisfy this
checkpoint by providing both centralized and integrated views of accessibility
features in the documentation.
12.3 Document default bindings.
(P1)
-
Document the default user agent input configuration (e.g., the default keyboard
bindings).
For user agent features
Techniques for checkpoint 12.3
Note: If the default input configuration is inconsistent
with conventions of the operating environment, the documentation should alert
the user.
12.4 Document changes. (P2)
-
Document changes from the previous version of the user agent to
accessibility features, including accessibility features of the user
interface.
- Accessibility features are those defined in checkpoint 12.2.
For user agent features
Techniques for checkpoint 12.4
12.5 Dedicated section on accessibility.
(P2)
- Provide a centralized view of all features of the user agent that benefit
accessibility in a dedicated section of the
documentation.
- The features that benefit accessibility are those defined in checkpoint 12.2.
For user agent features
Techniques for checkpoint 12.5
Note: The user agent satisfies this checkpoint
automatically by providing a centralized view of accessibility features to
satisfy checkpoint
12.2. However, developers are encouraged to integrate descriptions of
accessibility features into the documentation alongside other features, in
addition to providing a centralized view.
This normative
section defines what it means to conform to this document and explains how to
make a valid conformance claim. The following
are important conformance concepts.
- Conformance and conformance claims differ. This document
distinguishes conformance requirements and conformance claim
requirements. The sections on
unconditional conformance and
conditional conformance explain the conformance requirements. The section
on well-formed claims explains the claim
requirements (e.g., identification of the components that make up the user
agent, the operating environment in which they run, etc.) Here is a sample claim (expressed in HTML):
<p>On 14 July
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-UAAG10-20010714, level Double-A. Unsupported
content types: Video, Speech. Unsupported input modalities: Voice. (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>
- Modular conformance. A conforming user agent is not required to be a single piece
of software. In general, a conforming user agent will consist of several
coordinated components, such as a browser, a multimedia player, documentation
on the Web, etc. The current document places no restrictions on the type or
number of components that make up the "subject of a conformance claim", i.e., the user agent
(i.e., set of components) about which someone has made a conformance
claim.
- Conditional conformance. A user agent is not required to
satisfy every checkpoint in order to conform. This document allows "conditional conformance", which means
conformance to less than (or more than) a default set of requirements.
Claimants may not pick and choose which requirements they wish to satisfy in
order to conform conditionally; conditional conformance is governed by several
mechanisms described below:
- conformance levels,
- content type labels,
- input modality labels,
- selection label.
When a user agent conforms conditionally, a conformance claim about the user
agent must indicate how the set of satisfied requirements differs from the
default set; see the section on well-formed
claims.
- Applicability. Some checkpoints may not apply to a particular user agent because of the nature
of the user agent's user interface or the nature of the format(s) implemented
by the user agent. If a checkpoint (or portion of a checkpoint) doesn't apply,
the user agent is not required to satisfy it for conformance. A claimant must
state in a well-formed conformance claim which
checkpoints, if any, do not apply. See the section on
applicability for information about how to determine whether a checkpoint
applies.
In this document (notably in the checkpoints and in this section on
conformance), the terms "must", "should", and "may" (and related terms) are
used in accordance with RFC 2119 [RFC2119].
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, some software may conform to this document
but still be inaccessible to some users with disabilities. Some requirements of
this document may not benefit some users for some content, but the requirements
are expected to benefit many users with disabilities, for general purpose
content. For more information, please see the sections on known limitations of this document and restricted functionality and
conformance.
A user agent conforms unconditionally to this document if:
- it satisfies all of the requirements of all the checkpoints. Note that each
checkpoint statement includes one or more requirements. The requirements made
by a checkpoint include those associated with any content type labels for that checkpoint. Each
checkpoint also states whether the requirements are
for all content, for all rendered content, for user agent features, or for both
user agent features and content;
- for each checkpoint in
guideline 6, it satisfies the requirements by implementing APIs. For every other checkpoint, it satisfies
the requirements by implementing at least one mechanism other than an API. Note: The checkpoints
outside of guideline 6
may be satisfied by assistive technologies as well, but are required by the
current document to be satisfied by a conforming user agent. For example, checkpoint 9.3 involves navigation
that must be possible through the user interface, not just via an API. Note
that an assistive technology may be part of the
subject of a claim.
These requirements together form the "default" set of conformance requirements.
To allow user agents with different capabilities to conform, and to
facilitate comparisons of claims about different user agents, this document
defines allows conditional conformance. A user agent conforms conditionally if
it satisfies any set of requirements that results from starting with the default set of requirements and removing or adding
requirements according to these steps:
- Choose a conformance level; conformance
levels A or Double-A remove requirements from the default set.
- Remove the requirements associated with any unsupported content type labels. In order to conform
conditionally, a user agent must satisfy the requirements of at least one
content type label.
- Add requirements associated with any supported input modality label. Note:
In the default set of requirements, the only input device requirements relate
to keyboard input.
- If the user agent does not implement a
selection mechanism, remove the requirements of any checkpoints or
parts of checkpoints associated with the selection
label.
- Remove the requirements of any checkpoints or parts of checkpoints that do
not apply.
Since these steps may produce very different sets of checkpoints for
different user agents, a well-formed conformance
claim must indicate how the set of requirements chosen for the claim
differs from the default set. The checklist
[UAAG10-CHECKLIST] may
prove useful when documenting the details of a conditional conformance
claim.
The following example illustrates how to apply the above steps to determine
which requirements must be satisfied for conformance, and what would be
required as part of a well-formed conformance claim. This informative example does not illustrate a
complete user agent evaluation.
Consider a user agent with these capabilities:
- it supports keyboard and pointing device input;
- it renders text (in color) and implements:
- one audio format,
- two image formats,
- two other animation formats (besides video, which is considered an
animation format in this document);
- it feeds video to a plug-in for rendering;
- it doesn't support synthesized speech output;
- it implements a selection mechanism.
Step 1: Choose a conformance level.
The claimant wishes to conform at level Double-A. This establishes a set of
requirements consisting of all of the requirements of all the priority 1 and 2
checkpoints.
Step 2: Remove the requirements associated with any
unsupported content type labels.
The claimant wishes to claim conformance for the user agent's support of
text, images, audio, and video. The claimant does not wish to claim conformance
for other animation
formats.
The following content type labels are therefore relevant: VisualText,
ColorText, Image, Animation, Video, and Audio. This means that:
- the claimant must remove the set of requirements associated with the Speech
content type label.
- the claimant must satisfy the requirements associated with the other
content type labels.
Step 3: Remove the requirements of any checkpoints or parts of
checkpoints that do not apply.
Consider checkpoint 4.4, for example, which is associated with both the
Audio and Animation content type labels:
4.4 Slow multimedia.
(P1)
- Allow the user to slow the presentation rate of audio and animations (including video and animated
images).
- 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 and
animations whose
recognized role is to create a purely stylistic effect.
Suppose that:
- The claimant wishes to claim support for the two image formats, the one
audio format, and the one video format;
- The claimant does not wish to claim support for the other two animation
formats (e.g., because the user agent doesn't satisfy the requirements of checkpoint 4.4 for those
animation formats);
- The user agent does not implement any synchronized multimedia formats.
The resulting applicable requirements from this checkpoint would be:
- For the audio format: Allow the user to slow the presentation rate of
audio. For a prerecorded audio track including audio-only presentations,
provide at least one setting between 75% and 80% of the original speed.
- For the video format: Allow the user to slow the presentation rate of
video. For a visual track, provide at least one setting between 40% and 60% of
the original speed.
- For the image formats: None, since the Image content type label does not
include checkpoint checkpoint
4.4.
- Limitation of scope for any format: The user agent is not required to
satisfy the requirements of this checkpoint for audio and animations whose
recognized role is to create a purely stylistic effect.
The following requirements would not apply:
- 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. Note: The relevant applicability provision is provision three: control of a
content property that the subject cannot recognize. In this case, no format
implemented by the user agent supports synchronized multimedia.
Step 4: Add requirements related to the selection.
In this example, since the user agent implements a
selection mechanism, it must satisfy the requirements associated
with the selection label.
Step 5: Add requirements associated with any supported input
modality label.
In this example, the claimant does not wish to claim conformance for
complete operation for pointing device or voice input, so no requirements are
added.
Construct a well-formed conformance claim.
The following information is an excerpt of that required for a well-formed
claim:
- Conformance level satisfied: Double-A
- Information about the subject. Both the "main" user agent and the plug-in used to support video must be
identified in the claim (since the plug-in is the component used to satisfy the
requirements for video).
The user agent does not conform
unconditionally, therefore, the claim must also include the following
information (excerpted from a complete claim):
- A general statement about lack of support for the Speech content type
label: "This user agent does not support the requirements of the Speech content
type label. "
- A specific statement about content type support for checkpoint 4.4: "This user
agent satisfies the requirements of the Animation content type label for the
audio format A and the video format V. It does not satisfy the Animation
requirements for animation formats Y and Z."
- A specific statement about applicability for checkpoint 4.4: "The
synchronized multimedia requirements of checkpoint checkpoint 4.4 do not apply
because the user agent does not implement any formats that support synchronized
multimedia."
The following normative subsections provide detail that is relevant to both
unconditional and conditional conformance.
Each checkpoint definition indicates whether the requirements of the
checkpoint must be satisfied by the subject of the claim for:
- content only, i.e., the document
object only;
- rendered
content only;
- user agent features only, i.e., everything that is not content (such as components of the user
agent user interface, user preferences, the user agent
documentation, and the
user interface focus);
- both content and user agent features.
Many of the content-only and rendered content-only requirements also make
sense for the user agent user interface (e.g., allow the user to render
blinking text as motionless text). User agent developers are encouraged to
consider the content-only requirements when designing the user agent's user
interface.
The user agent may satisfy a content-only or rendered content-only
requirement with a mechanism that also involves user agent features.
For instance, to satisfy
checkpoint 4.9, the user agent may provide a single control for all volume
(including content and user interface features). Similarly, to satisfy checkpoint 3.3, the user
agent may offer a single configuration that turns off blinking in both content
and the user interface.
Note. Depending on the checkpoint,
content focus and selection requirements may be labeled as being
for content or user agent features or both. Content focus and selection are
"state variables" that straddle both worlds of content and user agent user
interface.
A user agent may conform by satisfying the checkpoint requirements of this
document for some, but not all,
implemented specifications and APIs. For example, a developer may implement
ten image formats but only wish to claim "Image" conformance for three of them.
In particular, the following requirements may be satisfied for some but not
all implemented specifications:
The user agent may satisfy the configuration requirements of this document
through configuration files (e.g., profiles, initialization files, themes,
etc.). For instance, style sheets might be used as a mechanism to satisfy the
highlight and configuration requirements of checkpoints 10.2 and 10.4. Any functionality that
is configurable through a configuration file should also be configurable
through the user
agent user interface. Furthermore, if configuration files may be
edited by hand, the user agent documentation should explain the configuration
file format, or refer to an explanation (such as a format specification).
For some of the checkpoints in this document (checkpoint 3.3, checkpoint 5.1, checkpoint 5.3, checkpoint 5.5, checkpoint 5.6), configuration is
preferred, but not required to satisfy the checkpoint in some circumstances.
For other checkpoints, the configuration requirement is considered as important
as the functionality being configured.
Since this document allows conformance by multiple software components
(e.g., a browser, a media player, and several plug-ins), there are likely to be
times when, to satisfy the configuration requirements of the document, each
component has to provide for configuration independently. To make configuration
easier for the user, components should share and inherit configurations
(including from the operating environment).
To satisfy the requirements of this document, developers are encouraged to
adopt
operating environment conventions and features that benefit
accessibility. When an operating environment feature (e.g., the operating
system's audio control feature, including its user interface) 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 environment 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.
Some of the checkpoints in this document involve operating environment
conventions. When a user agent runs in more than one operating environment
(e.g., a user agent implemented in Java on top of another operating system),
developers may satisfy the requirements of this document by following the
conventions of a single operating environment. Developers should follow the
conventions that benefit accessibility most, while meeting the developers'
design goals. For instance, some developers may prefer cross-platform
consistency over consistency with other user agents running in a given
operating environment, and this might affect which conventions would be
preferred.
User agents do not conform to this document on a per-resource basis; claims
are not as specific as "the user agent conforms for this particular Web page."
A user agent conforms if it satisfies the requirements of this document for
most general-purpose content, in ordinary operating conditions.
In some cases, an author may wish to limit the user agent's functionality
for specific reasons, such as to protect intellectual property rights, for
security reasons, or to provide a read-only view (allowing no user
interaction). Content that limits the functionality of the user agent in some
cases does not automatically invalidate a conformance claim. A valid
conformance claim remains valid as long as the user agent is capable of
satisfying the requirements of the document (i.e., the functionalities have
been implemented), and does so for most general-purpose content.
Note: The User Agent Accessibility Guidelines Working Group
recognizes that further work is necessary in the area of digital rights
management as it relates to accessibility. Digital rights management refers to
methods of describing and perhaps enforcing intellectual property associated
with Web resources.
Each conformance level defines a set of requirements, based on priority.
Note: Conformance levels are spelled out in text (e.g.,
"Double-A" rather than "AA") so they may be understood when rendered as
synchronized speech.
Each content type label defines a set of requirements related to support for
images, video, animations generally, visually displayed text (in color), and
synthesized speech.
- VisualText
- This content type label refers to all of the requirements related to the
visual rendering of text for the following checkpoints: 3.3, 4.1, and 4.2. To conform, the user
agent must
support visually rendered text.
- ColorText
- This content type label refers to all of the requirements related to text
foreground and background color for the following checkpoint: 10.4. To conform, the user
agent must
support more than one text foreground
color and more than one text background color.
-
Image
- This content type label refers to all of the requirements related to images
(excluding animated images) for the following checkpoints: 3.1, and 3.7. To conform, the user agent
must
implement at least one image format. The
image requirements apply to content that
is
recognized as distinct and that,
according to the encoding format, may be rendered as a coherent unit.
- Animation
- This content type label refers to all of the requirements related to animations (including video and animated
images) for the following checkpoints: 3.2, 4.4,
4.5, 4.7, and 4.8. To conform, the
user agent must implement
at least one animation format. The animation requirements apply to animation
content that is
recognized as distinct and that, according to the encoding format,
may be rendered as a coherent unit.
-
Video
- This content type label refers to all of the requirements related to video
for the following checkpoints: 2.5,
2.6, and 3.2. To
conform, the user agent must implement
at least one video format. The video requirements apply to video content that
is
recognized as distinct and that,
according to the encoding format, may be rendered as a coherent unit.
-
Audio
- This content type label refers to all of the requirements related to audio for the following checkpoints: 2.5, 2.6, 3.2, 4.4, 4.5, 4.7, 4.8, 4.9, 4.10, and 4.11 To conform, the user
agent must implement
at least one audio format. The audio requirements apply to audio content that
is
recognized as distinct and that,
according to the encoding format, may be rendered as a coherent unit.
- Speech
- This content type label refers to all of the requirements related to
synthesized speech for the following checkpoints: 4.12, 4.13, 4.14, 4.15, and 4.16. To conform, the
user agent must support
synthesized speech.
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 8.2.
Each input modality label defines a set of requirements related to support
for pointing device and voice input. Input device requirements in this document
are either stated generically (e.g., "input configuration" requirements) or as
keyboard-specific requirements (e.g., "keyboard API").
-
Pointer
- This input modality label refers to all of the input device requirements of
this document, applied to pointing device input. For keyboard-specific
requirements, substitute "pointing device input" for "keyboard." The set of
pointing device input requirements does not include the requirements of checkpoint 11.4.
-
Voice
- This input modality label refers to all of the input device requirements of
this document, applied to voice input. For keyboard-specific requirements,
substitute "voice input" for "keyboard." The set of voice input requirements
does not include the requirements of
checkpoint 11.4.
Note: Developers are encouraged to design user agents that
are at least partially operable through all three input modalities.
This document does not require the user agent to implement a selection mechanism in order to conform.
However, if the user agent does implement a selection mechanism, in order to
conform it must satisfy the relevant portions of the following checkpoints: 6.5, 7.1, 9.4, 10.2, 10.3, and 5.4. The Selection label refers to the selection requirements of
these checkpoints.
If a user agent does not implement a selection mechanism, then a well-formed claim must say so.
Note: This document does require implementation of both
content focus and user interface focus; see checkpoint 9.1 and checkpoint 9.2.
A checkpoint (or part of a checkpoint) applies unless 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,
associated
conditional content, fee link,
synchronization cue, client-side redirect, purpose of a table, 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 specified mechanisms
for
conditional content. HTML user agents are not expected to recognize
that a nearby paragraph is a text
equivalent for the image (when not marked up as such).
- 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 encoded in an unrecognized XML namespace;
- 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 unrecognized in a script. Some
input device behavior may be controlled by scripts in a manner that the user
agent cannot recognize. For example, when the author uses
event bubbling to dispatch events, the
user agent is not likely to recognize the full set of elements that may receive
those events; the user agent is expected to recognize which element has the explicitly associated event handler.
A claim is well-formed if meets the following conditions.
Condition 1: The claim must include the following information:
- The date of the claim.
- The guidelines title/version: "User Agent Accessibility Guidelines
1.0".
- The URI of the guidelines:
http://www.w3.org/WAI/UA/WD-UAAG10-20010714.
- 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 user agent name and version information. Version information must be
sufficient to identify the user agent (e.g., vendor name, version number, minor
release number, required patches or updates, natural language of the user
interface or documentation). The version information may refer to a range of
user agents (e.g., "this claim refers to all user agents version 6.x").
- The name and version number of the operating environment(s) in which the user
agent is running.
- If a conformance icon is part of a claim
on the Web, it must link to the W3C explanation of the icon.
Condition 2: The claim must include the following information if the user
agent conforms conditionally:
- Content type labels. Content type labels
are used in assertions that the subject either (1) does not satisfy the
requirements associated with the label (e.g., for a specific checkpoint, for
any checkpoint, etc.), or (2) does satisfy the requirements associated with the
label (e.g., for a particular format when satisfying the requirements of a
checkpoint). In order to conform conditionally, a user agent must satisfy the
requirements of at least one content type label.
- Input modality labels. Each input
modality label ("Pointer" or "Voice") is an assertion that the user agent
satisfies the requirements associated with the label.
- Selection label. If the user agent does not
implement a selection
mechanism, the claim must say so.
- A list of requirements (checkpoints or portions of checkpoints) that the
claim asserts do not apply.
Condition 3: At least one version of the claim must conform to the "Web
Content Accessibility Guidelines 1.0" [WCAG10], level A. This claim may
appear on the Web, on a CD-ROM, etc.
A well-formed claim should also include the following information:
This specification imposes no restrictions 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 if the following conditions are met:
- The claim is well-formed.
- It is verified that the user agent satisfies the default set of requirements, in addition to (or
except) those requirements added (or exempted) by the allowable mechanisms: conformance levels, content type labels, input modality labels, and applicability.
It is not currently possible to validate a claim entirely automatically.
Notes:
- The subject of the claim may consist of more than one software component,
and taken together they must satisfy all requirements that are not excluded
through the claim. These components may run on the user's computer or on a
server. This includes assistive technologies and
operating environment 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 6 as long as the
subject of the claim as a whole makes all content available through
those APIs.
- The document has been designed so that non-experts can determine the
validity of a claim. In some cases, a requirement might be clear, but without
documentation or feedback from developers (e.g., about implemented APIs), it may be difficult to verify that the
subject of the claim has satisfied the
requirement. Some checkpoints (e.g., those requiring developers to follow
conventions or implement specifications defined outside this document) are
inherently more open to interpretation than others.
- Ideally, the default user agent installation procedure should provide and
install all components that are part of a conformance claim. This is because,
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, etc.
This specification imposes no restrictions about:
- who may make a claim (e.g., vendors about their own user agents, third
parties about those user agents, journalists about user agents, etc.), or
- where claims may be published (e.g., on the Web or in paper
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
Recommendation available.
As part of a conformance claim, people may use a conformance icon (or,
"conformance logo") on a Web site, on user agent packaging, in documentation,
etc. A conformance icon does not represent that a claim is valid, only that a claim has been made. The
appearance of a conformance icon does not imply that W3C has reviewed the
claim.
It is inappropriate and meaningless to use a conformance icon on its own,
i.e., to use the icon without an associated
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.
This glossary is
normative. Some terms (or parts of explanations of terms) may not
have an impact on conformance.
Note: In this document, glossary terms generally link to
the corresponding entries in this section. These terms are also highlighted
through style sheets and identified as glossary terms through markup.
- Activate
- In this document, the verb "to activate" means (depending
on context) either:
The effect of activation depends on the type of enabled element or user
interface control. For instance, when a link is activated, the user agent
generally retrieves the linked Web
resource. When a form element is activated, it may change state
(e.g., check boxes) or may take user input (e.g., a text entry field).
-
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.
-
Animation
- In this document, an "animation" refers to content that, when rendered, creates a visual
movement effect automatically (i.e., without manual user interaction). This
definition of animation includes video and animated images. Animation
techniques include:
- graphically displaying a sequence of snapshots within the same region
(e.g., as is done for video and animated images). The series of snapshots may
be provided by a single resource (e.g., an animated GIF image) or from distinct
resources (e.g., a series of images downloaded continuously by the user
agent).
- scrolling text (e.g., achieved through markup or style sheets).
- displacing graphical objects around the viewport (e.g., a picture of a ball
that is moved around the viewport giving the impression that it is bouncing off
of the viewport edges). For instance, the SMIL 2.0 [SMIL20] animation modules explain
how to create such animation effects in a declarative manner (i.e., not by
composition of successive snapshots).
-
Applet
- An applet is a program (generally written in the Java
programming language) that is part of content,
and that the user agent executes.
- Application
Programming Interface (API), conventional input/output/device
API
- An application programming interface (API) defines how
communication may take place between applications.
Implementing APIs that are independent of a particular operating environment
(as are 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 conventional APIs for a particular
operating environment may reduce implementation costs for assistive technology
developers who wish to interoperate with more than one piece of software
running on that operating environment.
A "device API" defines how communication may take place
with an input or output device such as a keyboard, mouse, video card, etc.
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 "conventional input/output API" is one that
is expected to be implemented by software running on a particular operating
environment. For example, on desktop computers today, the conventional input
APIs are for the mouse and keyboard. For touch screen
devices or mobile devices, conventional input APIs may
include stylus, buttons, voice, etc. The graphical display and sound card are
considered conventional ouput devices for a graphical desktop computer
environment, and each has an associated 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 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.
- voice 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. For
example, the following very general definition of "assistive technology device"
comes from the (U.S.) Assistive Technology Act of 1998 [AT1998]:
Any item, piece of equipment, or product system, whether acquired
commercially, modified, or customized, that is used to increase, maintain, or
improve functional capabilities of individuals with disabilities.
-
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
- In this document, the term "audio" refers to content that
encodes pre-recorded sound.
- Audio-only
presentation
- An audio-only presentation is content 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 narration.
-
Audio track
- An audio object is content rendered as sound through an
audio
viewport. 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 (sometimes, "audio description")
is either a prerecorded human voice or a synthesized voice (recorded or
generated dynamically) describing the key visual elements of a movie or other
animation. The auditory description is
synchronized with (and possibly included as part of) 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 content (e.g., style sheets within a document,
that are associated with a document, or that are generated by a server).
- Captions
- Captions (sometimes, "closed captions") are text
transcripts that are
synchronized with other audio
tracks 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.
- Character encoding
- A "character encoding" is a mapping from a character set
definition to the actual code units used to represent the data. Please refer to
the Unicode specification [UNICODE] for more information
about character encodings. Refer to "Character Model for the World Wide Web"
[CHARMOD] for additional information about characters and character
encodings.
- Collated text
transcript
- A collated text transcript is a text equivalent of a movie or other 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.
- Conditional content
- Conditional content is content that, by format
specification, should be made available to users through the user interface,
generally under certain conditions (e.g., based on user preferences or
operating environment limitations). Some examples of conditional content
mechanisms include:
- The "
alt
" attribute of the IMG
element in HTML 4.
According to
section 13.2 of the HTML 4 specification ([HTML4]): "User agents must render
alternate text when they cannot support images, they cannot support a certain
image type or when they are configured not to display images.
OBJECT
elements in HTML 4.
Section 13.3.1 of the HTML 4 specification ([HTML4]) explains the conditional
rendering rules of (nested) OBJECT
elements. The rules select
among ordered alternatives according to user preferences or error
conditions.
- The
switch
element and test attributes in SMIL 1.0. Sections
4.3 and 4.4, respectively,
of SMIL 1.0
[SMIL] explain the conditional rendering rules of these
features.
- SVG 1.0
[SVG] also includes a
switch
element and several
attributes for conditional processing.
- The
NOSCRIPT
and NOFRAMES
elements in HTML 4
[HTML4]
allow the author to provide content under conditions when the user agent does
not support scripts or frames, or the user has turned off support for scripts
or frames.
Specifications vary in how completely they define how and when to render
conditional content. For instance, the HTML 4 specification includes the
rendering conditions for the "alt
" attribute, but not for the
"title
" attribute. The HTML 4 specification does indicate that the
"title
" attribute should be available to users through the user
interface ("Values of the title attribute may be rendered by user agents in a
variety of ways...").
Note: The Web Content Accessibility Guidelines 1.0 requires
that authors provide text equivalents for non-text content. This is generally
done by using the conditional content mechanisms of a markup language. Since
conditional content may not be rendered by default, the current document
requires the user agent to provide access to unrendered conditional content (checkpoint 2.3 and checkpoint 2.9)
as it may have been provided to promote accessibility.
-
Configure,
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 needs to 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 limitations of the
operating environment or hardware.
Both configuration and control may apply at different "levels": across
Web resources (i.e., at the user agent
level, or inherited from the operating environment), to the entirety of a
Web resource, or to components of a Web resource (e.g., on a per-element
basis).
A
global configuration is one that applies across elements of the
same Web resource, as well as across Web resources. A global configuration may
be implemented by more than one setting (e.g., per component of the user
agent). For instance, when a user agent consists of a browser that renders HTML
and a plug-in that renders SVG, to satisfy the global configuration
requirements of this document, the browser may provide one setting and the
plug-in another.
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" refers to a
component of the user
agent user interface.
-
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.
Empty
content is either a null value or a string consisting of zero
characters. For instance, in HTML, "alt=''
" sets the value of the
"alt
" attribute to the empty string. In some markup languages, an
element may have empty content (e.g., the HR
element in HTML).
- Device-independence
- Device-independence refers to the ability to make use of
software with any appropriate supported input or output device.
-
Document object,
Document Object Model (DOM)
- 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- or schema-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 kinds of data
through the user interface. Most of the requirements of this document apply to
the document object after its construction. However, a few checkpoints (e.g.,
checkpoint 2.7 and checkpoint 2.11) may
affect the construction of the document object.
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 (a 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, text source
- 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", or as the result of viewing a resource on the local
file system). The document source generally refers to the "payload" of the user
agent's request, and doesn't generally include information exchanged as part of
the transfer protocol. The document source is data that is prior to any repair
by the user agent (e.g., prior to repairing invalid markup). "Text source"
refers to document source that is composed of
text.
-
Documentation
- Documentation refers to information that supports the use
of a user agent. This information may be found in manuals, installation
instructions, the help system, tutorials, etc. Documentation may be distributed
(e.g., some parts may be delivered on CD-ROM, others on the Web). Refer to guideline 12 for information about
documentation requirements.
- Element, element type,
- This document uses the terms "element" and "element type"
in the sense employed by the XML 1.0 specification ([XML], section 3): an element type is
a syntactic construct of a Document Type Definition (DTD) for its application.
This sense is also relevant to structures defined by XML schemas. The document
also uses the term "element" more generally to mean a type of content (such as
video or sound) or a logical construct (such as a header or list).
-
Enabled element, disabled element
- An enabled element is a piece of
content with associated behaviors that may be activated through the
user interface or through an API. The set of elements that a user agent
enables is generally derived from, but is not limited to, the set of
interactive elements defined by implemented markup languages.
Some elements may only be enabled elements for part of a user session. For
instance, an element may be disabled by a script as the result of user
interaction. Or, an element may only be enabled during a given time period
(e.g., during part of a SMIL 1.0 [SMIL] presentation). Or, the user
may be viewing content in "read-only" mode, which may disable some
elements.
A disabled element is a piece of content
that is potentially an enabled element, but is not in the current session.
Generally, disabled elements will be interactive elements that are not enabled in
the current session. This document distinguishes disabled elements (not
currently enabled) from non-interactive elements (never enabled).
For the requirements of this document, user
selection does not constitute user interaction with enabled
elements. See the definition of content
focus.
Note: Enabled and disabled elements come from content; they
are not part of the user
agent user interface.
Note: The term "active element" is not used in this
document since it may suggest several different concepts, including:
interactive element, enabled element, an element "in the process of being
activated" (which is the meaning of ':active' in CSS2 [CSS2], for example).
-
Equivalent (for content)
- The term "equivalent" is used in this document as it is
used in the Web Content Accessibility Guidelines 1.0 [WCAG10]:
Content is "equivalent" to other content when both fulfill essentially the
same function or purpose upon presentation to the user. In the context of this
document, the equivalent must fulfill essentially the same function for the
person with a disability (at least insofar as is feasible, given the nature of
the disability and the state of technology), as the primary content does for
the person without any disability.
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.).
Each markup language defines its own mechanisms for specifying
conditional content, and these mechanisms may be used by authors to
provide text 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 environment, etc.). Some markup languages allow authors to
specify that a script, called an event handler, be executed when
the event occurs. An event handler is "explicitly associated with an
element" when the event handler is associated with that element
through markup or the DOM. The term "event
bubbling" describes a programming style where a single event
handler dispatches events to more than one element. In this case, the event
handlers are not explicitly associated with the elements receiving the events
(except for the single element that dispatches the events).
Note: The combination of HTML, style sheets, the Document
Object Model (DOM) and scripting is commonly referred to as
"Dynamic HTML" or DHTML. However, as there is no W3C specification that
formally defines DHTML, this document only refers to event handlers and
scripts.
-
Explicit user request
- In this document, the term "explicit user request" refers to any user
interaction with a control
provided by the user
agent user interface (not those in content), the focus, or
selection. Control behavior should be
documented.
Some examples of explicit user requests include when the user selects "New
viewport", responds "Yes" to a prompt in the user agent's user interface,
configures the user agent to behave in a certain way, or changes the selection
or focus with the keyboard or pointing device.
Note: Users make mistakes. For example, a user may
inadvertently respond "yes" to a prompt when they meant "no." 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 is 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
- In this document, the term "content focus" refers to a
user agent mechanism that satisfies all of the following properties:
- It designates zero or one element in content
that is either
enabled or
disabled. (In general, the focus should only designate enabled
elements, but it may also designate disabled elements.)
- The user may "set" content focus (programmatically or through the user
interface) on an enabled element without triggering the associated
behaviors.
- It has state. The user may prefer to always move the content focus manually
from one element to another.
- It may be used (programmatically or through the user interface) to trigger
the behaviors associated with an enabled element. This is generally implemented
by making the focus respond to input device events (often just keyboard
events).
User interface mechanisms may resemble content focus, but do not satisfy all
of the properties. For example, text editors often implement a "caret" that
indicates the current location of text input or editing. The caret may have
state and may respond to input device events, but it does not enable users to
activate the behaviors associated with enabled elements.
The user interface focus shares the properties of the content focus except
the first: the user interface focus designates zero or one control of the user agent user interface that has associated
behaviors (e.g., radio button, text box, menu, etc.).
On the screen, the content focus may be
highlighted using colors, fonts, graphics, magnification, etc. The
content focus may also be highlighted when rendered as synthesized speech, for
example through changes in speech prosody. The dimensions of the rendered
content focus may exceed those of the viewport.
In this document, each viewport is expected to have at most one content
focus and at most one user interface focus. This document includes requirements
for content focus only, for user interface focus only, and for both. When a
requirement refers to both, the term "focus" is used.
When several viewports
coexist, at most one viewport's content focus or user
interface focus responds to input events; this is called the current focus.
-
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. Graphical highlight mechanisms include dotted boxes,
underlining, and reverse video. Synthesized speech highlight mechanisms include
alterations of voice pitch and volume ("speech prosody").
- Image
- In this document, an "image" refers to content that encodes static (i.e., unmoving)
visual information. See also the definition of
animation.
- Input configuration
- An input configuration is the mapping of user agent
functionalities to some user
interface input 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 documented (per checkpoint 12.3]). Input
configurations may be affected by author-specified bindings (e.g., through the
"accesskey" attribute of HTML 4 [HTML4]).
- Interactive element,
non-interactive element,
- An interactive element is piece of content that, by
specification, may have associated behaviors to be executed or carried out as a
result of user or programmatic interaction. For instance, the interactive
elements of HTML 4 [HTML4] include: links, image maps,
form elements, elements with a value for the "longdesc" attribute, and elements
with event
handlers explicitly associated with them (e.g., through the various
"on" attributes). The role of an element as an interactive element is subject
to applicability. A non-interactive element is an
element that, by format specification, does not have associated behaviors. The
expectation of this document is that interactive elements become enabled
elements in some sessions, and non-interactive elements never become
enabled elements.
- 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.
-
Normative,
informative
- As used in this document, the term "normative" refers to
"that on which the requirements of this document depend for their most precise
statement." What is normative is required for
conformance (though the conformance scheme of this document allows
claimants to exempt certain normative provisions as long as the claim discloses
the exemption). What is identified as "informative" (sometimes,
"non-normative") is never required for conformance.
- Operating
environment
- The term "operating environment" refers to the environment
that governs the user agent's operation, whether it is an operating system or a
programming language environment such as Java.
-
Override
- In this document, the term "override" means that one
configuration or behavior preference prevails over another. Generally, the
requirements of this document involve user preferences prevailing over author
preferences and user agent default settings and behaviors. Preferences may be
multi-valued in general (e.g., the user prefers blue over red or yellow), and
include the special case of two values (e.g., turn on or off blinking text
content).
- 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,
images, and audio cues.
This document includes requirements that the user be able to view the
original author-supplied content associated with a placeholder. To satisfy
these requirements, the user agent might render the content in place of the
placeholder or in a separate viewport (leaving the placeholder as is). A
request to view the original content associated with a placeholder is considered an explicit
user request to render that content.
This document does not require user agents to include placeholders in the document
object. A placeholder that is 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).
-
Plug-in
- A plug-in is a program that runs as part of the user agent
and that is not part of content.
Users generally choose to include or exclude plug-ins from their user
agent.
-
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 the viewport, but it may exceed the spatial or temporal dimensions of
the viewport (see the definition of rendered content for more information about
viewport dimensions). 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 determine the point of
regard in a number of ways, including based on viewport position in content,
content focus,
selection, etc. A user agent should not change the point of regard
unexpectedly as this may disorient the user.
-
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. In
operating environments 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 prompt me before
doing X, always do X without prompting me, never do X but tell me when you
could have, never do X and never tell me that you could have, 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, synthesized 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 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. On the other hand,
behaviors, style, meaning encoded in a script, and
markup in an unfamiliar XML namespace may not be recognized by the user agent
as easily or at all. 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 that the user agent makes available to the user's senses of
sight and hearing (and only those senses for the purposes of this document).
Any content that causes an effect that may be perceived through these senses
constitutes rendered content. This includes text characters, images, style
sheets, scripts, and anything else in content that, once processed, may be
perceived through sight and hearing.
The term "rendered text" refers to text content
that is rendered in a way that communicates information about the characters
themselves, whether visually or as synthesized speech.
- 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
conditional content that is required by format specification,
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."
Information encoded in scripts may be difficult for a user agent to recognize 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).
- Selection, current
selection
- In this document, the term "selection" refers to a user
agent mechanism for identifying a range of
content (e.g., text, images, etc.). Generally, user agents limit
selection to text content (e.g., one or more fragments of text). The selection may be structured (based on the
document tree) or unstructured (e.g., text-based). The range may be empty.
On the screen, the selection may be
highlighted using colors, fonts, graphics, magnification, etc. The
selection may also be highlighted when rendered as synthesized speech, for
example through changes in speech prosody. The dimensions of the rendered
selection may exceed those of the viewport.
The selection may be used for a variety of purposes: for cut and paste
operations, to designate a specific element in a document for the purposes of a
query, as an indication of point of
regard, etc.
The selection has state. It may be set programmatically or through the user
interface.
In this document, each viewport is expected to have at most one selection.
When several viewports
coexist, at most one viewport's selection responds to input events; this is
called the current selection.
See the section on the selection label for
information about implementing a selection and
conformance.
Note: Some user agents may also implement a selection for
designating a range of information in controls of the user agent user interface. The current document
only includes requirements for a content
selection mechanism.
- 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 conformance requirements to
other specifications (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.
- 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
- As used in this document a "text element" adds text characters to either content or the
user interface. Both in the Web Content Accessibility Guidelines 1.0
[WCAG10] and in this document, text elements are presumed to produce
text that can be understood when rendered visually, as synthesized speech, or
as Braille. Such text elements benefit at least these three groups of users:
- visually-displayed text benefits users who are deaf and adept in reading
visually-displayed text;
- synthesized speech benefits users who are blind and adept in use of
synthesized speech;
- braille benefits users who are blind, and possibly deaf-blind, and adept at
reading braille.
A text element may consist of both text and non-text data. For instance, a
text element may contain markup for style (e.g., font size or color), structure
(e.g., heading levels), and other semantics. The essential function of the text
element should be retained even if style information happens to be lost in
rendering.
A user agent may have to process a text element in order to have access to
the text characters. For instance, a text element may consist of markup, it may
be encrypted or compressed, or it may include embedded text in a binary format
(e.g., JPEG).
"Text content" is content that is composed of one or more text elements. A
"text equivalent" (whether in content or the user interface) is an
equivalent composed of one or more text elements. Authors generally
provide text equivalents for content by using the
conditional content mechanisms of a specification.
A "non-text element" is an element (in content or the user interface) that
does not have the qualities of a text element. "Non-text content" is composed
of one or more non-text elements. A "non-text equivalent" (whether in content
or the user interface) is an
equivalent composed of one or more non-text elements.
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). Both text
elements and non-text elements should be understood as "pre-rendering" content
in contrast to the "post-rendering" content that they produce.
-
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 other 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 voice-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 (e.g., menus, buttons, prompts,
etc.) and mechanisms (e.g., selection and focus) provided by the user agent
("out of the box") that are not created by
content.
- the "content user interface", i.e., the enabled elements that are part of content, such
as form elements, 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-only presentation
- A visual-only presentation is content consisting
exclusively of one or more visual
tracks presented concurrently or in series. A silent movie is an
example of a visual-only presentation.
-
Visual track
- A visual object is content rendered through a graphical viewport. Visual objects include graphics,
text, and visual portions of movies and other animations. 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 object or software
object. A visual track may be text-based or graphic. A visual track may be
static or involve
animation.
-
Views,
viewports
- The user agent renders content through one or more viewports.
Viewports include windows, frames, pieces of paper, loudspeakers, virtual
magnifying glasses, etc. A viewport may contain another viewport (e.g., nested
frames). User interface controls such as prompts, menus, alerts, etc. are not
viewports.
When the dimensions (spatial or temporal) of rendered content exceed the
dimensions of the viewport (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.), the user agent provides mechanisms such as scroll
bars and advance and rewind controls so that the user can access the rendered
content "outside" the viewport.
When several viewports
coexist, only one has the current
focus at a given moment. This viewport is
highlighted to make it stand out.
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); refer to 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.
Note: In this document, bracketed labels such as "[HTML4]"
link to the corresponding entries in this section. These labels are also
identified as references through markup.
There are two recommended ways to refer to the "User Agent Accessibility
Guidelines 1.0" (and to W3C documents in general):
- References to a specific version of "User Agent Accessibility Guidelines
1.0". For example, use the "this version" URI to refer to
the current document: http://www.w3.org/WAI/UA/WD-UAAG10-20010714/.
- References to the latest version of "User Agent Accessibility Guidelines
1.0". Use the "latest version" URI to refer to the most recently published
document in the series: http://www.w3.org/WAI/UA/UAAG10/.
In almost all cases, references (either by name or by link) should be to a
specific version of the document. W3C will make every effort to make this
document indefinitely available at its original address in its original form.
The top of this document includes the relevant catalog metadata for specific
references (including title, publication date, "this version"
URI, editors' names, and copyright information).
An XHTML 1.0
[XHTML10] paragraph including a reference to this specific document
might be written:
<p>
<cite><a href="http://www.w3.org/WAI/UA/WD-UAAG10-20010714/">
"User Agent Accessibility Guidelines 1.0"</a></cite>,
I. Jacobs, J. Gunderson, E. Hansen, eds.,
W3C Working Draft, 14 July 2001.
The <a href="http://www.w3.org/WAI/UA/UAAG10/">latest
version</a> of this document is available at
http://www.w3.org/WAI/UA/UAAG10/.</p>
For very general references to this document (where stability of content,
anchors, etc., is not required), it may be appropriate to refer to the latest
version of this document. In this case, please use the "latest version" URI at
the top of this document.
See also information about making conformance
claims to this document.
- [CSS1]
- "CSS, level 1
Recommendation", B. Bos, H. Wium Lie, eds., 17 December 1996,
revised 11 January 1999. This W3C Recommendation is
http://www.w3.org/TR/1999/REC-CSS1-19990111.
- [CSS2]
- "CSS, level 2
Recommendation", B. Bos, H. Wium Lie, C. Lilley, and I. Jacobs,
eds., 12 May 1998. This W3C Recommendation is
http://www.w3.org/TR/1998/REC-CSS2-19980512/.
- [DOM2CORE]
-
"Document Object Model (DOM) Level 2 Core Specification", 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/.
- [RFC2046]
- "Multipurpose Internet
Mail Extensions (MIME) Part Two: Media Types", N. Freed, N.
Borenstein, November 1996.
- [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/.
Some of the references in this section become normative if they are used to
satisfy the requirements of
guideline 6 and
guideline 8.
- [AT1998]
- The Assistive
Technology Act of 1998, 13 November 1998, United States P.L.
105-394.
- [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/
- [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/.
- [MATHML20]
-
"Mathematical Markup Language (MathML) Version 2.0", D. Carlisle, P.
Ion, R. Miner, N. Poppelier, et al., 21 February 2001. This W3C Recommendation
is http://www.w3.org/TR/2001/REC-MathML2-20010221/.
-
[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/.
- [SMIL20]
- Synchronized
Multimedia Integration Language (SMIL 2.0) Specification, J. Ayars,
et al., eds., 1 March 2001. This W3C Working Draft is
http://www.w3.org/TR/2001/WD-smil20-20010301/. The latest version of SMIL 2.0
is available at http://www.w3.org/TR/smil20.
- [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-SUMMARY]
- An appendix to this document provides a summary of the goals and structure of User Agent
Accessibility Guidelines 1.0.
-
[UAAG10-TECHS]
- "Techniques for User
Agent Accessibility Guidelines 1.0", I. Jacobs, J. Gunderson, E.
Hansen, eds. The latest draft of the techniques document is available at
http://www.w3.org/WAI/UA/UAAG10-TECHS/.
- [UNICODE]
- "The Unicode
Standard, Version 3.1". This technical report of the Unicode Consortium is available at
http://www.unicode.org/unicode/reports/tr27/. This is a revision of "The
Unicode Standard, Version 3.0", The Unicode Consortium, Addison-Wesley
Developers Press, 2000. ISBN 0-201-61633-5. Refer also to
http://www.unicode.org/unicode/standard/versions/. For information about character
encodings, refer to Unicode Technical
Report #17 "Character Encoding Model".
-
[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), Harvey Bingham, Al Gilman, Jon Gunderson (Chair of the Working
Group, University of Illinois, Urbana-Champaign), Eric Hansen (Educational
Testing Service), Ian Jacobs (Team Contact, W3C), Tim Lacy (Microsoft), Charles
McCathieNevile (W3C), David Poehlman, Mickey Quenzer, Gregory Rosmaita
(Visually Impaired Computer Users Group of New York City), and Rich
Schwerdtfeger (IBM).
Many thanks to the following people who have contributed through review and
past participation in the Working Group: Paul Adelson, Kitch Barnicle, Olivier
Borius, Judy Brewer, Dick Brown, 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, Marja-Riitta Koivunen, Peter Korn, Josh Krieger, Catherine
Laws, Aaron Leventhal, Greg Lowney, Susan Lesch, Scott Luebking, William
Loughborough, Napoleon Maou, Peter Meijer, Karen Moses, Masafumi Nakane, Mark
Novak, Charles Oppermann, Mike Paciello, David Pawson, Michael Pederson, Helen
Petrie, Michael Pieper, Richard Premack, Jan Richards, Hans Riesebos, Joe
Roeder, Lakespur L. Roca, Madeleine Rothberg, 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.