User Agent Accessibility Guidelines 1.0
W3C Working Draft, 8 July 2002
- This version:
-
http://www.w3.org/WAI/UA/WD-UAAG10-20020708/
- Latest version:
-
http://www.w3.org/WAI/UA/UAAG10/
- Previous version:
-
http://www.w3.org/WAI/UA/WD-UAAG10-20010831/
- Editors:
- Ian Jacobs, W3C
Jon Gunderson, University of Illinois at
Urbana-Champaign
Eric Hansen, Educational Testing
Service
- Authors and Contributors:
- See acknowledgements.
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Copyright © 1999 - 2002 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 is the 8 July 2002 Working Draft of "User Agent Accessibility
Guidelines 1.0". Working Draft status is described in section
5.2.1 of the Process Document. This document incorporates the resolutions
of the User Agent Accessibility Guidelines Working Group to issues raised
during the second Candidate Recommendation period for this document (which
began in September 2001). The list of changes to this
document includes information about modifications to checkpoints, conformance
mechanisms, and other editorial clarifications. Most of the modifications to
checkpoints were the result of the UAWG's discussions with developers over the
past ten months.
As of the publication of this document, the UAWG has decided to keep some
checkpoints for which there is little implementation experience. This revision
of the document does not include that information, but the UAWG expects to make
that information available at its Web site. The UAWG will continue to seek
implementation experience for these checkpoints.
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 this document 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.
This document specifies requirements that, if satisfied by user agent developers, will lower barriers
to accessibility. This document includes:
- This introduction, which provides context for understanding the
requirements listed in section 2.
- Section 2 explains twelve general principles of
accessible design, called "guidelines". Each guideline consists of a list of
requirements, called "checkpoints", which must be satisfied in order to conform
to this document.
- Section 3 explains how to make claims that
software components satisfy the requirements of section 2.
- An appendix offers a summary of this document's principal goals and
structure; see [UAAG10-SUMMARY].
- A second appendix lists all the checkpoints for convenient reference (e.g.,
as a tool for developers to evaluate software for conformance); see
[UAAG10-CHECKLIST].
A separate document, entitled "Techniques for User Agent Accessibility
Guidelines 1.0" (the "Techniques document" from here on)
[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 in the Techniques document 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.
Developers, W3C Working Groups, users, and others are encouraged to contribute
techniques.
"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, XHTML, XML, SVG,
SMIL, MathML, 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. The "XML Accessibility Guidelines (XAG)"
[XAG10]
explains the responsibilities of XML format designers; many XAG requirements
make sense for non-XML formats as well.
- 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. The "Web Content Accessibility Guidelines
(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 2.10) 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.
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 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 consist of more than
one component. For example, these components might include a Web browser,
one or more media players, and documentation distributed with the software or
available on the Web.
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 4.9
to checkpoint
4.13). 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 4.9).
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.
- 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
document [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.
A number of themes run through the guidelines in this document. The
following in particular are worth noting before you read the guidelines.
User control
The user must have control over the rendering and behavior of content and
the user interface. For instance, many of the requirements in this document
give the user manual control over behavior that would otherwise occur
automatically. This document strikes a balance between honoring author
preferences and ensuring that the user can create an accessible
environment.
Configurability
This document includes requirements for users with a variety of
disabilities, in part because some users may have more than one disability. In
some cases, it may appear that two requirements contradict each other. For
instance, a user with a physical disability may prefer that the user agent
offer more automatic behavior (to reduce demand for physical effort) than a
user with a cognitive disorder (for whom automatic behavior may cause
confusion). Many of the requirements in this document involve configuration as
one way to ensure that a functionality designed to improve accessibility for
one user does not interfere with accessibility for another. Also, since a
default user agent setting may be useful for one user but interfere with
accessibility for another, this document prefers configuration requirements
over default setting requirements. Finally, there may be some cases where, for
some content, a feature required by this document is ineffective or causes
content to be less accessible, making it imperative that the user be able to
turn off the feature.
To avoid the risk that users are overwhelmed by an abundance of
configuration options, this document includes requirements that promote ease of
configuration and documentation of accessibility features.
Independence
Many requirements in this document promote independence on a variety of
axes:
- Input and output device independence. This document includes some
requirements to promote device-independence natively, and requirements for
interoperability with assistive technologies that provide complementary input
and output functionalities.
- Spatial independence. Some users may not navigate effectively in
two-dimensional space (e.g., users who do not use a pointing device) or may be
constrained to one-dimensional output (e.g., users of audio-only output).
- Temporal independence. Some users (e.g., users with a physical or cognitive
disability) may not be able to interact with content that changes over time, or
interaction with content that is time-sensitive.
Relation to other specifications
This document promotes conformance to other specifications as part of
accessible design. Conformance to specifications makes it easier to design
assistive technologies, and helps ensure that built-in accessibility functions
are implemented.
This document also includes some requirements to implement an accessibility
feature that may only be optional in another specification.
In rare cases, a requirement in UAAG 1.0 may conflict with a requirement in
another specification. UAAG 1.0 does not include requirements for resolving
this conflict, but the authors of this document anticipate that developers will
consider accessibility implications when determining how to resolve the
conflict.
The twelve guidelines in this document state general principles for the
development of accessible user agents. Each guideline includes:
- The guideline number.
- The guideline title.
- 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 parts. Some parts are normative (i.e., relate to conformance);
others are informative only.
- The checkpoint number.
- The checkpoint title. This title is not a requirement, just a phrase to
help readers remember an important requirement made by the checkpoint
provision(s). (Informative)
- The priority of the checkpoint. (Normative)
- A link to the Techniques document [UAAG10-TECHS] for more
information about the checkpoint: rationale, who benefits, example techniques,
references, and more. (Informative)
- The checkpoint provisions, which include one or more requirements that must
be satisfied by the user agent (i.e., the subject of
the claim) for conformance. (Normative)
- Optional: Techniques that are sufficient for satisfying
all or part of a checkpoint provision. (Normative)
- Optional: Normative inclusions and exclusions. These are
normative qualifications about what is required (inclusion) or is not required
(exclusion) to satisfy the checkpoint. Two important types of inclusions that
may appear are:
- A "content/rendered content/user agent
feature/both" label that indicates 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 only, or for both content and user agent features. The label only
appears when necessary to disambiguate the checkpoint.
- Content type labels, which are explained
in the section on conformance.
(Normative)
- Optional: Notes about the checkpoint (beginning with the
word "Note"). The 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. (Informative)
Note: A user agent may conform to this document without
satisfying every checkpoint. See the section on conditional conformance for more
information about how to eliminate some checkpoints and still conform.
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. The Techniques document [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 in most operating environments, 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
6.7. 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 input 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.
Checkpoint definitions
- Ensure that the user can operate
through keyboard input alone any user agent functionality available through the
user interface.
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.
- Allow the user to activate, through keyboard input alone, all
event handlers of any input
device event type that are explicitly associated with the element designated by
the content focus.
- In order to satisfy provision
one, the user must be able to activate as a group all event handlers of the
same input device event type.
Normative inclusions and exclusions
- 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 (e.g., a mouse down event followed by a
mouse drag event followed by a mouse up event).
- 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.
- Conformance labels:
Events.
Note: 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.
-
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.
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
6.5, a text equivalent for each such message must be available through an
API. See also
checkpoint 6.6 for
requirements for programmatic notification 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:
- Both manual and automatic selection of which conditional content to render are
important to accessibility.
- Both structured navigation and unstructured access to content are important
to accessibility.
- 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).
Checkpoint definitions
- Render content
according to format specification (e.g., for a markup language or style sheet
language).
Normative inclusions and exclusions
- 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).
- 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.
- 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.
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.).
- For content
authored in text formats, provide a view of the text source. For the purposes of this
checkpoint, a text format is any media object given an Internet media type of
"text" (e.g., text/plain, text/html, or text/*) as defined in RFC 2046
[RFC2046], section 4.1.
Normative inclusions and exclusions
- The user agent is only required to satisfy this checkpoint for text formats
that are part of a conformance claim; see the section on conformance and implementing specifications for
more information. However, user agents should provide a text view for all
implemented text formats. A user agent would also satisfy this checkpoint by
providing a source view for any text format, not just implemented text
formats.
- Allow
configuration to provide access to each piece of unrendered conditional content "C".
- 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 allowing the user to query 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.
Sufficient techniques
- To satisfy provision one, the configuration may be a switch that, for all
content, turns on or off the access mechanisms described in provision two.
- To satisfy provision two, 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).
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).
- For rendered content where user input is
only possible within a finite time interval controlled by the user agent, allow
configuration to provide a view where user
interaction is time-independent.
Sufficient techniques
- The user agent may satisfy this checkpoint by pausing processing
automatically to allow for user input, and resuming processing on explicit user request. When
this technique is used, pause at the end of each time interval where user input
is possible. In the paused state:
- Alert the user that the rendered content has been paused
(e.g., highlight the "pause" button in a multimedia player's control
panel).
- Highlight which enabled elements are
time-sensitive.
- Allow the user to interact with the enabled elements.
- Allow the user to resume on explicit user request (e.g., by
pressing the "play" button in a multimedia player's control panel; see also checkpoint 4.5).
- The user agent may satisfy this checkpoint by generating a
time-independent ("static") view, based on the original content,
that offers the user the same opportunities for interaction. The static view
should reflect the structure and flow of the original time-sensitive
presentation; orientation cues will help users understand the context for
various interaction opportunities.
Normative inclusions and exclusions
- When satisfying this checkpoint for a real-time presentation, the user
agent may discard packets that continue to arrive after the construction of the
time-independent view (e.g., when paused or after the construction of a static
view).
- 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).
Note: If the user agent satisfies this checkpoint by
pausing automatically, it may be necessary to pause more than once when there
are multiple opportunities for time-sensitive user interaction. 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. See also checkpoint 3.5, which involves client-driven content
retrieval.
- Allow
configuration or control to render text transcripts, collated text transcripts,
captions, and audio descriptions at the same time
as the associated audio tracks and visual tracks.
Note: This checkpoint is an important special case of checkpoint 2.1.
- Respect synchronization cues (e.g., in
markup) during rendering.
Normative inclusions and exclusions
- Conformance labels:
Video, Audio.
Note: This checkpoint is an important special case of checkpoint 2.1.
-
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.
Sufficient techniques
- 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. Note, however, that additional information that would enable
more helpful repair might be available but not "near" the missing conditional
content. 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 designated by the URI
reference.
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).
- Allow at
least two configurations for when the user agent recognizes that conditional content required by
the format specification is present but
empty:
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.
- Allow
configuration to render all conditional content
automatically.
- As part of satisfying
provision one, provide access according to specification, or where unspecified,
by applying one of the techniques described in checkpoint 2.3: 1a, 2a, or
1b.
Normative inclusions and exclusions
- The user agent is not required to render all conditional content at the
same time in a single viewport.
- For all content.
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.).
- Allow
configuration not to render content in unsupported natural languages, when that content
would otherwise be rendered. Content "in a natural language" includes
pre-recorded spoken language and text in a given script, i.e., writing system.
- When configured per provision
one, indicate to the user in context that author-supplied content has not been
rendered.
Normative inclusions and exclusions
- This checkpoint is designed primarily to benefit users who access content
serially, allowing them to skip portions of content that would be unusable if
rendered as "garbage". This checkpoint does not require the user agent to allow
different configurations for different natural languages.
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,
automatic content retrieval, 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 might pose accessibility problems. Requirements
for interactive control of rendered content are part of guideline 4.
Checkpoint definitions
- Allow
configuration not to render background image
content.
Sufficient techniques
- The user agent may satisfy this checkpoint with a configuration to not
render any images, including background images. However, user agents
should satisfy this checkpoint by allowing users to turn off background images
alone, independent of other types of images in
content.
Normative inclusions and exclusions
- This checkpoint must be satisfied for all
applicable implemented formats; see the section on conformance and implementing specifications.
- When configured not to render background images, the user agent is not
required to retrieve them until the user requests them explicitly; see checkpoint 2.3 for
information about access to conditional content.
- 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".
- Conformance 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.
- Allow
configuration not to render audio, video, or animated image content, except on explicit user request.
Sufficient techniques
- The user agent may satisfy this checkpoint by making video and animated
images invisible and audio silent, but this technique is not
recommended.
Normative inclusions and exclusions
- 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 that is not an explicit user request (e.g.,
when the user activates a link).
- This checkpoint must be satisfied for all
applicable implemented formats; see the section on conformance and implementing specifications.
- When configured not to render audio, video, or animated images except on
explicit user request, the user agent is not required to retrieve them until
the user requests them explicitly; see checkpoint 2.3 for information about access to conditional
content.
- Conformance labels: Animation, Video,
Audio.
Note: See
guideline 4 for additional requirements related to the control of rendered
audio, video, and animated images.
- Allow
configuration to render animated or blinking text content as motionless, unblinking text.
Blinking text is text whose visual rendering alternates between visible and
invisible, at any rate of change.
Sufficient techniques
- 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.
Note: Animation (a rendering effect) differs from streaming
(a delivery mechanism). Streaming content might be rendered as an animation
(e.g., an animated stock ticker or vertically scrolling text) or as static text
(e.g., movie subtitles, which are rendered for a limited time, but do not give
the impression of movement).
-
Allow configuration not to execute any executable
content (e.g., scripts and
applets).
Normative inclusions and exclusions
- This checkpoint does not apply to plug-ins and other programs that are not part
of content.
Note: 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.
- Allow
configuration so that the user agent only retrieves content on
explicit user request.
Normative inclusions and exclusions
- When the user chooses not to retrieve (fresh) content, the user agent may
ignore that content; buffering is not required.
- The user agent is not required to satisfy this checkpoint for "client-side
redirects", i.e., author-specified instructions that a piece of content is
temporary and intermediate, to be replaced by content that results from a
second request. Authors (and Webmasters) should use the redirect mechanisms of
HTTP instead of client-side redirects.
- This checkpoint only applies when the user agent (not the server)
automatically initiates the request for fresh content.
Note: For example, if an HTML author has used a
META
element for automatic content retrieval, allow configuration to
override the automatic behavior with manual confirmation.
-
Allow configuration not to render image content.
Sufficient techniques
- The user agent may satisfy this checkpoint by making images invisible, but this technique is
not recommended.
Normative inclusions and exclusions
- This checkpoint must be satisfied for all
applicable implemented formats; see the section on conformance and implementing specifications.
- When configured not to render images, the user agent is not required to
retrieve them until the user requests them explicitly; see checkpoint 2.3 for
information about access to conditional content.
- Conformance labels:
Image.
Checkpoints: 4.1,
4.2, 4.3,
4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, 4.12, 4.13, 4.14
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, and
navigate it quickly. User agents rendering audio have to allow the user to
control the audio volume globally and to allow the user to control
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.
Checkpoint definitions for visually rendered text
- Allow global configuration of the
scale of visually rendered text. Preserve
text size differences when the user changes the scale.
- As part of satisfying provision one,
provide a configuration option to override rendered text sizes
specified by the author or user agent defaults.
- As part of satisfying provision one,
offer a range of text sizes to the user that includes at least:
- the range offered by the conventional utility available in the operating environment that
allows users to choose the text size (e.g., the font size), or
- if no such utility is available, the range of text sizes supported by the
conventional APIs of the
operating environment for drawing text.
Sufficient techniques
- The user agent may satisfy provision one of this checkpoint through a
number of mechanisms, including zoom, magnification, and allowing the user to
configure a reference size for rendered text (e.g., render text at 36 points
unless otherwise specified). For example, for CSS2 [CSS2] user agents, the 'medium'
value of the 'font-size' property corresponds to a reference size.
Note: The user agent's default reference size of rendered
text may vary among user agents. Refer, for example to the Scalable Vector
Graphics specification
[SVG] for information about scalable rendering.
- 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.
- As part of satisfying provision one,
offer a range of font families to the user that includes at least:
- the range offered by the conventional utility available in the operating environment that
allows users to choose the font family, or
- if no such utility is available, the range of font families supported by
the conventional APIs of the
operating environment for drawing text.
Sufficient techniques
- For text that cannot be rendered properly using the
user's preferred font family, the user agent may substitute an alternative font
family.
Note: For example, allow the user to specify that all text is to be rendered in a particular
sans-serif font family.
- 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.
- As part of satisfying provision one,
offer a range of colors to the user that includes at least:
- the range offered by the conventional utility available in the operating environment that
allows users to choose colors, or
- if no such utility is available, the range of colors supported by the
conventional APIs of the
operating environment for specifying colors.
Normative inclusions and exclusions
- Color includes black, white, and greys.
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 10.2 for more
information about highlight styles.
Checkpoint definitions for multimedia presentations and other
presentations that change continuously over time
- Allow the user to slow the presentation rate
of rendered audio and animations (including video
and animated images).
- As part of satisfying provision one, for a
visual track, provide at least one
setting between 40% and 60% of the original speed.
- As part of satisfying provision one, 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 (per checkpoint 2.6). Below 80%,
the user agent is not required to render the audio
track.
Normative inclusions and exclusions
- The user agent is not required to satisfy this checkpoint for audio and
animations whose recognized role is to create a purely
stylistic effect. Purely stylistic effects include background sounds,
decorative animated images, and effects caused by style sheets.
- Conformance labels: Animation, Audio.
Note: 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).
- Allow the user to stop, pause, and resume
rendered audio and animations (including video and animated
images) that last three or more seconds at their default playback rate.
- Allow the user to navigate efficiently
within audio and animations (including video and animated
images) that last three or more seconds at their default playback rate.
Sufficient techniques
- The user agent may satisfy the navigation requirement of provision two
through forward and backward sequential access techniques (e.g., advance three
seconds), or direct access techniques (e.g., play starting at the 10-minute
mark), or some combination.
Normative inclusions and exclusions
- When serial techniques are used to satisfy provision two, the user agent is
not required to play back content during serial advance or rewind (though doing
so may help orient the user).
- When the user pauses a real-time audio or animation, the user agent may
discard packets that continue to arrive during the pause.
- This checkpoint applies to content that is either rendered automatically
(e.g., on load) or on explicit request from the user.
- The user agent is not required to satisfy this checkpoint for audio and
animations whose recognized role is to create a purely
stylistic effect; see checkpoint
4.4 for more information about what constitutes a stylistic effect.
- Conformance labels: Animation, Audio.
Note: Respect synchronization cues, per checkpoint 2.6.
- For
graphical viewports, allow configuration so that captions
synchronized with a visual track are not
obscured by it.
Sufficient techniques
- Render captions "on top" of the visual track and, as part of satisfying checkpoint 4.3, allow the
user to configure the foreground and background color of the rendered captions
text.
- Render captions and video in separate
viewports so that the user may position them independently.
Checkpoint definitions for audio volume control
- Allow global configuration of the
volume of all rendered audio, with an option to override
audio volumes specified by the author or user agent defaults.
- As part of satisfying provision one,
allow the user to choose zero volume (i.e.,
silent).
Note: User agents should allow configuration of volume
through available operating
environment controls.
- Allow independent control of the volumes of rendered audio sources synchronized to play
simultaneously.
Normative inclusions and exclusions
- The user control required by this checkpoint includes the ability to override author-specified volumes for the
relevant sources of audio.
- The user agent is not required to satisfy this checkpoint for audio whose
recognized role is to create a purely
stylistic effect; see checkpoint
4.4 for more information about what constitutes a stylistic effect.
- Conformance labels:
Audio.
Note: 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 checkpoint 4.10 for information about controlling the volume
of synthesized speech.
Checkpoint definitions for synthesized speech rendering
- Allow
configuration of the synthesized speech rate, according to the full range
offered by the speech synthesizer.
Normative inclusions and exclusions
- Conformance labels:
Speech.
Note: The range of synthesized speech rates offered by the
speech synthesizer may depend on natural language.
- Allow control of
the synthesized speech volume, independent of other sources of audio.
Normative inclusions and exclusions
- The user control required by this checkpoint includes the ability to override author-specified synthesized speech
volume.
- Conformance labels:
Speech.
Note: See also checkpoint 4.8.
- Allow configuration of synthesized speech
characteristics according to the full range of values offered by the speech
synthesizer.
Normative inclusions and exclusions
- Conformance labels:
Speech.
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.
- Allow
configuration of synthesized speech pitch. Pitch refers to the average
frequency of the speaking voice.
- Allow
configuration of synthesized speech pitch range. Pitch range specifies a
variation in average frequency.
- Allow
configuration of synthesized speech stress. Stress refers to the height of
"local peaks" in the intonation contour of the voice.
- Allow
configuration of synthesized speech richness. Richness refers to the
richness or brightness of the voice.
Normative inclusions and exclusions
- Conformance labels:
Speech.
Note: This checkpoint is more specific than checkpoint
4.11: 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.
- Provide support
for user-defined extensions to the synthesized speech dictionary.
- Provide support
for spell-out: where text is spelled one character at a time, or according to
language-dependent pronunciation rules.
- Allow at least two configurations for speaking numerals: one
where numerals are spoken as individual digits, and one where full numbers are
spoken.
- Allow at least two configurations for speaking punctuation:
one where punctuation is spoken literally, and one where punctuation is
rendered as natural pauses.
Normative inclusions and exclusions
- Conformance labels:
Speech.
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.
Checkpoint definitions related to style sheets
- Allow the user to choose from and apply
alternative author style sheets (such as linked
style sheets).
- Allow the user to choose from and apply
at least one user style sheet.
- Allow the user to ignore author and user
style sheets.
Normative inclusions and exclusions
- This checkpoint only applies to user agents that support
style sheets.
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. Unexpected changes to the point of regard – what the user
is presumed to be viewing – may cause users to lose track of how many viewports are open, which viewport has the
current focus, etc. If carried out
automatically, these changes might go unnoticed (e.g., by some users with
blindness) or be disorienting (e.g., to some users with a cognitive
disability). This guideline includes requirements for control of opening and
closing viewports, the relative position of graphical viewports, changes to
focus, and inadvertent form submissions.
Checkpoint definitions
- Allow
configuration so that if a viewport opens without explicit user request, its content focus does not automatically
become the current focus.
Sufficient techniques
- Configuration is preferred, but is not required if the content focus can
only ever be moved on explicit user
request.
- 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.
- Allow
configuration so that viewports only open on explicit user request.
- When configured per provision one, 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.
Sufficient techniques
- Configuration is preferred, but is not required if viewports can only ever
open on explicit user request.
Normative inclusions and exclusions
- If a viewport (e.g., a frame set) contains other viewports, these
requirements only apply to the outermost container viewport.
- 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.
Note: Generally, viewports open automatically as the result
of instructions in content. See also checkpoint 5.1 (for
control over changes of focus when a viewport opens) and checkpoint 6.6 (for
programmatic notification of changes to the user interface).
- Ensure that when a viewport's selection or
content focus changes, it is at least partially in the viewport after the change.
Normative inclusions and exclusions
- Conformance labels: Selection.
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.
- Allow
configuration to prompt the user to confirm (or cancel) any
form submission.
Sufficient techniques
- Configuration is preferred, but it not required if forms can only ever be
submitted on explicit user request.
Note: Examples of automatic form submission include:
script-driven submission when the user changes the state of a particular form
control associated with the form (e.g., via the pointing device), submission
when all fields of a form have been filled out, and submission when a
"mouseover" or "change" event
occurs.
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 offer
specialized access.
Checkpoint definitions
-
Provide programmatic read access to XML content by making available
all of the information items defined by the W3C XML Infoset
[INFOSET].
-
Provide programmatic read access to HTML content by making available all of the
following information items defined by the W3C XML Infoset
[INFOSET]:
- Document Information item: children, document element, base URI,
charset
- Element Information items: element-type name, children, attributes,
parent
- Attribute Information items: attribute-type name, normalized value,
specified, attribute type, references, owner element
- Character Information items: character code, parent element
- Comment Information items: content, parent
-
If the user can modify HTML and XML content through the user interface
(e.g., through form controls), allow for the same modifications
programmatically.
-
As part of satisfying
checkpoint 6.1, conform to the following modules of the W3C Document Object
Model DOM Level 2 Core
Specification [DOM2CORE] and exporting bindings
for the interfaces they define:
- for HTML: the Core module.
- for XML: the Core and XML modules.
-
As part of satisfying provision one:
- Export the normative bindings specified in the DOM Level 2 Core
Specification [DOM2CORE] (namely, for Java
[JAVA] and ECMAScript
[ECMASCRIPT] operating environments).
- For other environments, the bindings exported to satisfy provision one must
be publicly documented.
Normative inclusions and exclusions
- The user agent is not required to export the bindings outside of the user
agent process.
Note: Please refer to the "Document Object Model (DOM)
Level 2 Core Specification" [DOM2CORE] for information about
HTML and XML versions covered.
- For content
other than HTML and XML, provide
structured programmatic read access to content,
and write access to those parts of content that the user can modify through the
user interface.
- As part of satisfying provision one,
implement at least one API according
to this API cascade:
- The API is defined by a W3C Recommendation, or the API is
publicly documented and 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,
Normative inclusions and exclusions
- "Structured programmatic access" means access through an API to recognized
information items of the content (such as the information items of the XML
Infoset
[INFOSET]). Plain text has little structure, so an API that provides
access to it will be correspondingly less complex than an API for XML content.
For content more structured than plain text, an API that only provides access
to a stream of characters does not satisfy the requirement of providing
structured programmatic access. This document does not otherwise define what is
sufficiently structured access.
- 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.
Note: This checkpoint addresses content not covered by checkpoint 6.1 and checkpoint 6.2.
- For graphical user agents, provide
programmatic read access to visually rendered information.
- As part of satisfying provision one,
implement at least one API according to the API cascade described in provision
2 of checkpoint 6.3.
Note: The API used to provide access to visually rendered
information should provide access to both structured information and
pixel-level information. User agents should also provide information about the
correspondence (in both directions) between locations in content and related locations in the
rendering structure.
-
Provide programmatic read access to user agent user interface
controls.
-
Provide programmatic write access for those user agent user interface
controls that the user can modify through the user interface.
-
As part of satisfying provisions one and two, implement at least one API
according to the API cascade described in provision 2 of checkpoint 6.3.
Note: APIs used to satisfy the requirements of this
checkpoint may be independent of a particular operating environment (e.g., 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.
- Provide programmatic notification of
changes to content,
user interface controls, selection, content focus, and user interface focus.
- As part of satisfying provision one,
implement at least one API according to the API cascade of provision 2 of checkpoint 6.3.
Normative inclusions and exclusions
- The user agent is not required to provide notification of rendering
changes (e.g., due to an animation effect or an effect caused by a style
sheet), just changes to the content itself.
- Conformance labels: Selection.
- For both content and user agent.
Note: For instance, provide programmatic notification when
user interaction in one frame causes automatic changes to content in
another.
-
Implement
APIs for the keyboard as follows:
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.
- For an API implemented to satisfy
requirements of this document, support the character encodings required for
that API.
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.
-
For user agents that implement Cascading Style
Sheets (CSS), provide programmatic access to style sheets by
conforming to the CSS module of the W3C Document Object Model (DOM) Level 2 Style Specification
[DOM2STYLE] and exporting bindings for the interfaces it
defines.
-
As part of satisfying provision one:
- Export the normative bindings specified in the CSS module of the
DOM) Level 2 Style Specification
[DOM2STYLE] (namely, for Java [JAVA] and
ECMAScript [ECMASCRIPT] operating
environments).
- For other environments, the bindings exported to satisfy provision one must
be publicly documented.
Normative inclusions and exclusions
- For the purposes of satisfying this checkpoint, Cascading Style Sheets
(CSS) are defined by either CSS Level 1
[CSS1] or CSS Level 2 [CSS2].
- The user agent is not required to export the bindings outside of the user
agent process.
Note: Please refer to the "Document Object Model (DOM)
Level 2 Style Specification" [DOM2STYLE] for information
about CSS versions covered.
- For APIs implemented to satisfy the
requirements of this document, ensure that programmatic exchanges proceed in a
timely manner.
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 also increases predictability for users and for
developers of assistive
technologies. These guidelines explain what users will expect from the look
and feel of the user interface, keyboard conventions, documentation, etc. These
guidelines also include information about accessibility features that the user
agent should adopt rather than reimplement.
The chapter on conformance explains more on the use of operating environment features as part of
conformance.
Checkpoint definitions
- Follow operating environment
conventions that benefit accessibility when
implementing the selection, content focus, and user interface focus.
Normative inclusions and exclusions
- Conformance labels: Selection.
Note: This checkpoint is an important special case of checkpoint 7.3. See also checkpoint 9.1 and checkpoint 9.2.
- Ensure that default input configurations of the user
agent do not interfere with operating environment
accessibility conventions (e.g., for keyboard accessibility).
Note: Information about operating environment accessibility
conventions is available in the Techniques document
[UAAG10-TECHS]. See checkpoint 11.5 for information about the user agent's
default input configuration.
-
Follow operating
environment conventions that benefit accessibility. In particular, follow
conventions that benefit accessibility for
user interface design, keyboard configuration, product installation, and documentation.
Normative inclusions and exclusions
- 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.
Note: Some of these conventions (e.g., sticky keys, mouse
keys, show sounds, etc.) are discussed in the Techniques document
[UAAG10-TECHS].
- Follow operating environment
conventions to indicate the input configuration.
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 checkpoint 11.5 for
information about the user agent's default input configuration.
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.
Checkpoint definitions
- Implement the accessibility
features of specifications (markup languages, style sheet languages, metadata
languages, graphics formats, etc.).
Normative inclusions and exclusions
- This checkpoint applies to both W3C-developed and non-W3C
specifications.
- For the purposes of this checkpoint, an accessibility feature of a
specification is either:
- one identified as such in the specification, or
- one that allows the author to satisfy any requirement of the "Web Content
Accessibility Guidelines 1.0" [WCAG10].
- 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.
- For all content.
Note: The Techniques document
[UAAG10-TECHS] provides information about the accessibility features
of some specifications, including W3C specifications.
- 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].
Sufficient techniques
- 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.
Normative inclusions and exclusions
- 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.
- 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.
- For all content.
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].
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.).
Checkpoint definitions
- 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.
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. See checkpoint 7.1 for
information about implementing content focus according to operating environment
conventions.
-
Provide a user interface focus.
Note: See checkpoint 7.1 for information about implementing user
interface focus according to operating environment
conventions.
-
Allow the user to move the content focus to any enabled element in the viewport.
-
Allow configuration so that the content focus of
a viewport only changes on explicit user
request. Configuration is not required if the content focus only ever
changes on explicit user request. See checkpoints 5.1 and 6.6 for more information
about focus changes.
- If
the author has not specified a navigation order, allow at least forward
sequential navigation, in document order, to each element in the set
established by provision one.
Normative inclusions and exclusions
- The user agent may also include disabled elements in the navigation
order.
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.
- 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 (e.g., via the "back button"), restore the saved values
for the point of regard, content focus, and selection.
Normative inclusions and exclusions
- The viewport history associates values for these three state variables (point of regard, content focus, and selection) with a particular document
object. If the user returns to a state in the history and the user agent
retrieves new content, the user agent is not required to restore the saved
values of the three state variables.
- Conformance labels: Selection.
- Allow
configuration so that moving the
content focus to or from an enabled element does not
automatically activate any explicitly associated event handlers of any event type.
Normative inclusions and exclusions
- Conformance labels:
Events.
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.
-
For the element with content focus, make
available the list of input device event types for which there are event handlers explicitly associated
with the element.
Normative inclusions and exclusions
- Conformance labels:
Events.
Note: For example, allow the user to query the element with
content focus for the list of input device event types, 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.
- As part of satisfying provision three of checkpoint 9.3, allow the same
sequential navigation in reverse document order.
- As part of satisfying provision three of checkpoint 9.3, the user agent must
not include disabled elements in the navigation
order.
Note: This checkpoint is a special case of checkpoint 9.3.
-
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.
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 environment
conventions for indicating the result of a search (e.g., selection or
content focus).
-
Allow the user to navigate efficiently to and among important structural
elements in rendered content.
-
As part of satisfying provision one, allow forward and backward sequential
navigation.
Note: This specification intentionally does not identify
which "important elements" must be navigable as this will vary by
specification. 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.
- Allow
configuration of the set of important elements identified in checkpoints 9.9 and 10.4.
- As part of satisfying provision one,
allow the user to include and exclude element types in the set.
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.
- information about specific elements, such as the dimensions of a table, the
length of an audio clip, the structure of a form, etc.
- information about relationships among elements, such as between table cells
and related table headers.
- information about the structure of content, e.g., through an outline view
of a document.
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.
Checkpoint definitions
-
For graphical user agents that render tables, allow the user to view the
header information associated with any table cell in the same viewport and at
the same time as the table cell.
Sufficient techniques
- The user agent may satisfy this checkpoint with a technique frequently
employed by spreadsheet applications: the user agent fixes the position of
headers in the viewport and allows the user to scroll through associated data
cells. Through horizontal and vertical alignment, the data cells and header
cells are visually associated.
Normative inclusions and exclusions
- This checkpoint refers only to cell/header relationships that the user
agent can recognize.
10.2 Highlight selection, content focus, enabled elements, visited
links. (P1)
Techniques for checkpoint 10.2
- Allow global configuration to highlight the following four classes of
information in each viewport: the selection, content focus, enabled elements, and recently
visited links.
- For graphical user interfaces, as part
of satisfying provision one, allow at least one configuration where the
highlight mechanisms for the four classes of information:
- differ from each other, and
- do not rely on rendered text foreground
and background colors alone.
- For graphical user interfaces, as part
of satisfying provision one, if a highlight mechanism involves text size, font
family, rendered text foreground and background
colors, or text decorations, offer at least the following range of values:
- for text size, the range required by provision two of checkpoint 4.1.
- for font family, the range required by provision two of checkpoint 4.2.
- for text foreground and background colors and decorations, the range
offered by the conventional utility available in the operating environment for
users to choose rendered text colors or decorations (e.g., the standard font
and color dialog box resources supported by the operating system). If no such
utility is available, the range supported by the conventional APIs of the
operating environment for specifying text colors or drawing text.
- Highlight enabled elements according to the
granularity specified in the format. For example, an HTML user agent rendering
a PNG image as part of a client-side image map is only required to highlight
the image as a whole, not each enabled region. An SVG user agent rendering an
SVG image with embedded graphical links is required to highlight each (enabled) link that may be rendered
independently according to the SVG specification.
Normative inclusions and exclusions
- Conformance labels: Selection.
Note: Examples of highlight mechanisms for selection and
content focus include foreground and background color variations, underlining,
distinctive synthesized speech prosody, border styling, 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. Graphical highlight mechanisms that generally do
not rely on rendered text foreground and background color alone include
underlines or border styling. Per checkpoint 7.1, follow operating environment conventions
that benefit accessibility when implementing the selection and content focus.
For instance, if specified at the level of the operating environment, inherit
the user's preferences for selection styles.
- As part of satisfying provision two
of checkpoint 10.2,
allow configuration through a single
setting.
Normative inclusions and exclusions
- Conformance labels: Selection.
- 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, and other
labels that are part of the content).
Normative inclusions and exclusions
- What constitutes a label is defined by each markup language specification.
For example, in HTML, a heading (
H1
-H6
) is a label
for the section that follows it, a CAPTION
is a label for a table,
the "title
" attribute is a label for its element, etc.
- The user agent is not required to generate a label for an important element
when no label is present in content. The user agent may generate a label when
one is not present.
- A label is not required to be text only.
Note: This outline view will provide the user with a
simplified view of content (e.g, a table of contents). 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 checkpoint 9.10 for additional configuration options.
- 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, and
- information about the type, size, and natural language of linked Web
resources.
Normative inclusions and exclusions
- The user agent is not required to compute or make available information
that requires retrieval of linked Web
resources.
Checkpoint definitions for the user interface
- Allow global configuration to highlight the
viewport with the current focus (including
any frame that takes current focus).
- For graphical viewports, as part of
satisfying provision one, allow at least one configuration where the highlight
mechanism does not rely on rendered text foreground
and background colors alone (e.g., use a thick outline).
- If the techniques used to satisfy
provision one involve rendered text size, font
family, rendered text foreground and background
colors, or text decorations, offer the same ranges of values required by
provision three of
checkpoint 10.2.
Note: See checkpoint 7.1 for information about implementing highlight
mechanisms according to operating environment
conventions.
- 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.).
Sufficient techniques
- The user agent may calculate the relative position according to content
focus position, selection position, or viewport position, depending on how the
user has been browsing.
- The user agent may indicate the proportion of content viewed in a number of
ways, including as a percentage, as a relative size in bytes, etc. See checkpoint 1.3 for more information
about text versions of messages to the user, including messages about position
information.
Normative inclusions and exclusions
- For two-dimensional renderings, relative position includes both vertical
and horizontal positions.
- This checkpoint does not require the user agent to present information
about retrieval progress. However, for streaming content, viewport
position may be closely tied to retrieval progress.
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. An input configuration is the
set of "bindings" between user agent functionalities and user interface input mechanisms.
The chapter on conformance explains more about configuration requirements and conformance.
Checkpoint definitions
- Provide information to the user about
current user preferences for input configurations.
Sufficient techniques
- 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). See related checkpoints 12.2,
12.3, and
12.5.
- Provide a centralized view of the
current author-specified input configuration.
Sufficient techniques
- The user agent may satisfy this checkpoint by providing different views for
different input modalities (keyboard, pointing device, voice, etc.).
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.
- Allow the user to override
any binding that is part of the user agent default input configuration.
Normative inclusions and exclusions
- 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.
Note: See also checkpoints 11.5, 11.7, and 12.3.
- As
part of satisfying checkpoint
11.3 for the keyboard, 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.
- For
each functionality in the set required by checkpoint 11.5, allow the user to
configure a single-key binding. A single-key binding is one where a single
key press performs the task, with zero modifier keys.
Sufficient techniques
- The requirements of provision two 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).
Normative inclusions and exclusions
- In this checkpoint, "key" refers to a physical key of the keyboard (rather
than, say, a character of the document character
set).
- The user agent is not required to allow the user to override
conventional bindings for the operating environment (e.g.,
for access to help).
- Provision two does not require single physical key bindings for character
input, only for the activation of user agent functionalities.
- If the number of physical keys on the keyboard is less than the number of
functionalities required by checkpoint 11.5, provision two does not require the user
agent to allow single-key bindings for all of the functionalities. The user
agent should give preference to those functionalities listed in provision one
of that checkpoint.
- For user agent features.
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
6.7.
- 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, and navigate efficiently 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 a new resource;
- add a URI to favorites (i.e., bookmarked resources);
- view favorites;
- reload a resource;
- interrupt a request to reload a resource;
- for graphical viewports: navigation forward and backward through rendered
content by approximately the height of the viewport;
- for user agents that render content in lines of (at least) text: move point
of regard to next line, and previous line.
Sufficient techniques
- The user agent may satisfy the functionality of entering a URI for a new
resource in a number of ways, including by prompting the user, or by moving the
user interface focus to a user
interface control for entering URIs
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 addressed by the configuration requirements of checkpoint 11.3.
-
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).
Normative inclusions and exclusions
- This checkpoint does not require that user profiles be portable, i.e.,
removable from the user agent to be reread by a different instance of the
agent. Portable user profiles are very useful, however.
- For user agent features.
- For graphical user agent user interfaces
with tool bars, allow the user to configure the position of
controls on those tool bars.
- Offer a predefined set of controls that
may be added to or removed from tool bars.
- Allow the user to restore the default
tool bar configuration.
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. For
instance, 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 (checkpoints 12.2, 12.3, and 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).
See checkpoint 7.3 for
information about following system conventions for documentation.
Checkpoint definitions
-
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].
-
Document all user agent features that benefit accessibility.
Sufficient techniques
- 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.
Normative inclusions and exclusions
- 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, and the API requirements of
guideline 6).
- For user agent features.
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.
-
Document the default user agent input configuration (e.g., the
default keyboard bindings).
Sufficient techniques
- If the user agent does not allow the user to override the default user
agent input configuration (see
checkpoint 11.3), the documentation used to satisfy this checkpoint also
satisfies checkpoint
11.1.
Note: Documentation should warn the user whenever the
default input configuration is inconsistent with conventions of the operating
environment.
-
Document changes from the previous version of the user agent to features
that benefit accessibility, including features of the user interface.
- As part of satisfying checkpoint 12.2, provide
a centralized view of all features of the user agent that benefit
accessibility, in a dedicated section of the
documentation.
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 8 July
2002, UserAgent 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-UAAG10-20020708, level Double-A. Supported
conformance labels Image, Animation, Audio, Events, and Selection. Unsupported
conformance labels: Video, Speech, Pointer, and Voice. A <a
href="http://example.com/checkpoints">list</a> of formats used to
satisfy the requirements, and of checkpoints that do not apply 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 set of components about which someone has made a
conformance claim.
- Conditional conformance. A user agent may conform to this
document without satisfying every checkpoint. This document allows "conditional conformance", which means
conformance to fewer than (or more than) a default set of requirements.
Claimants do not arbitrarily choose which requirements they wish to satisfy in
order to conform conditionally; conditional conformance is governed by rules
for adding and removing well-defined sets of requirements. Each set is
identified by a
conformance labels. These mechanisms are called:
- Conformance levels,
- Content type labels,
- Events label,
- Selection label.
- Input modality labels,
When a user agent conforms conditionally, a conformance claim 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 section on known limitations of this document, and the section on
restricted functionality and
conformance.
A user agent conforms unconditionally to this document if:
- It satisfies the
default set of conformance requirements, defined to be all of the
requirements of all of the provisions of all the checkpoints, as well as all of
the normative inclusions and exclusions that
qualify the checkpoints, and
- It satisfies these requirements as follows:
- For each checkpoint in
guideline 6, the requirements are satisfied by implementing APIs;
- For all other checkpoints, the requirements are satisfied through at least
one mechanism (e.g., user interface feature or configuration file) 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.
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; for
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.
- If the user agent does not satisfy the requirements associated with the Events label, remove those
requirements.
- If the user agent does not implement a
selection mechanism, or if the user agent does not satisfy the requirements
associated with the Selection label,
remove those requirements.
- 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.
- 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 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 functionalities to allow keyboard access to event handlers originally designed to
be activated through a pointing device.
- 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: Identify requirements associated with content type
labels.
The claimant wishes to claim conformance for the user agent's support of
images, audio, and video. The claimant does not wish to claim conformance for
other animation formats.
The following content type labels are therefore relevant: Image, Animation,
Video, and Audio. This means that:
- the user agent is not required to satisfy the set of requirements
associated with the Speech content type label. The user agent may still satisfy
some of them.
- the user agent must satisfy the requirements associated with the other
content type labels.
Step 3: Identify requirements related to event handlers.
In this example, the user agent supports functionalities that promote
input-device independent access to
event handlers. Therefore, the claimant may rightly claim conformance for
the requirements associated with the Events
label.
These requirements are optional for conformance. However, if the claimant
does include the events label in the claim, the associated requirements must be
satisfied.
Step 4: Identify 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: Identify 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. The user agent may support partial operation through pointing device and
voice input.
Step 6: Identify 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 rendered
audio and animations (including video and animated
images).
- As part of satisfying provision one, for a visual track, provide at least one
setting between 40% and 60% of the original speed.
- As part of satisfying provision one, 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 (per
[#Trespect-sync-cues]). Below 80%, the user agent is not required to render the
audio track.
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 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 the third one: control of a
content property that the subject cannot recognize. In this case, no format
implemented by the user agent supports synchronized multimedia.
See the section on conformance and implementing
specifications for more information about identifying formats that are used
to satisfy the requirements of this document.
Construct a well-formed conformance claim.
With the information gathered above, it is possible to starting building a
conformance claim. A claim might include the following information:
- 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 support for the Events label: "This user agent satisfies
the requirements related to the Events label."
- A specific statement about support for the Selection label: "This user agent
satisfies the requirements related to the Selection label."
- 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.
The requirements of certain checkpoints might apply equally well to content
or to user agent user interface features. When it is necessary to remove
ambiguity about the scope of a checkpoint, the checkpoint includes a label to
indicate whether the requirements must be satisfied:
- for content only, i.e., the document object only;
- for 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);
- for 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 4.7, 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.
In general, a user agent is only required to satisfy the requirements of
this document for a subset of implemented specifications;
these specifications must be named in a
well-formed conformance claim. For example, the user agent may implement
ten image formats, but a developer may only wish to claim "Image" conformance for three of them. In
the well-formed claim, the developer must list the three formats used to
satisfy the Image requirements. The developer is thus "rewarded" for improving
user agent accessibility for three image formats.
There are several checkpoints, however, that must be satisfied for
all applicable implemented specifications,
otherwise the intent of the checkpoint may not be met. For instance, checkpoint 3.3 involves
turning off blinking and animated text. Since there is a risk that these
rendering effects may trigger seizures in people with photosensitive epilepsy,
it is important that the user be able to turn them off in all cases (whether
the specification is named in a conformance claim or not).
For a given conformance claim, the user agent must satisfy all checkpoints
in this document for at least those specifications named in the claim (e.g.,
format specifications, style sheet specifications, API specifications,
operating environment conventions, etc.). The user agent is not required to
satisfy all checkpoints for all implemented specifications, except for the
following cases:
- The user agent must satisfy checkpoint 3.3 for all specifications that cause animated or
blinking text effects (e.g., markup languages or style sheet
specifications).
- If the claim includes the Image
content type label, the user agent must satisfy checkpoint 3.1 and
checkpoint 3.6 for all image
formats.
- If the claim includes one of the
Animation, Video, Audio content type labels, the user agent
must satisfy checkpoint
3.2 for all animation, video, or audio formats, respectively.
- If the claim includes the Audio
content type label, the user agent must satisfy checkpoint 4.7 for all
audio formats.
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 checkpoint 10.2. 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 (a format specification, for example).
For some of the checkpoints in this document (checkpoints 3.3, 5.1, 5.3, and 5.5), 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 those of 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 4.7, 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, the author's content may limit the user agent's functionality
for specific reasons, such as to protect intellectual property rights, 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 satisfies the requirements of this document 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.
Some of the requirements of this document have security implications:
communication through APIs, allowing programmatic read and write access to
content and user interface control, etc. This document assumes that features
required by this document will be built on top of an underlying security
architecture. Consequently, unless permitted explicitly in a checkpoint (as in
checkpoint 6.5), this document
grants no conformance exemptions based on security issues.
Consider the example of a form control that allows the user to enter a
password. Graphical user agents commonly display typed characters as asterisks
(or display nothing). The user agent should not communicate asterisks to
assistive technologies, but the real password, properly encrypted.
Appropriate user agent behavior with respect to security (and more generally
as well) also depends on the user's context. For instance, hiding typed
passwords with asterisks is much less important for someone in a room alone
than for someone in a crowded room. Similarly, unencrypted passwords rendered
as synthesized speech should not be broadcast in a crowded room, but may pose
no security risk if the user is wearing an earphone.
For information related to security, refer to "XML-Signature Syntax and
Processing"
[XMLDSIG] and "XML Encryption Syntax and Processing" [XMLENC].
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, animations, video, audio, and synthesized speech.
- Image
- This content type label refers to all of the requirements related to images
(excluding animated images) for the following checkpoints: 3.1 and 3.6. To conform, the user agent
must implement at least one image format. The
user agent must satisfy these requirements for all
implemented image formats; see the section on
conformance and implementing specifications. 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,
and 4.5. To conform, the
user agent must implement at least one animation format.
The user agent must satisfy the requirements of checkpoint 3.2 for all implemented animation formats; see the
section on conformance and implementing
specifications. 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 user agent must satisfy the requirements of checkpoint 3.2 for all implemented video formats; see the section
on conformance and implementing specifications.
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, and 4.8. To conform, the
user agent must implement at least one audio format. The
user agent must satisfy the requirements of checkpoints 3.2 and 4.7 for all implemented audio formats; see the section
on conformance and implementing specifications.
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: 4.9, 4.10, 4.11, 4.12, and 4.13. 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.
The following checkpoints are designed to augment user agent support for
event-driven behavior specified by the author: 1.2, 9.5, and 9.6. Satisfying these
checkpoints will promote input device independence and thus enable users with
some disabilities to make better use of content designed for a single input
device (generally a pointing device). The Events
label refers to the requirements of these checkpoints.
A conforming user agent is not required to satisfy these requirements.
However, if a user agent does not implement these requirements, then a well-formed claim must say so.
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: 5.4, 6.6, 7.1, 9.4, 10.2, and 10.3. 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.
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 the three input modalities of keyboard,
pointing device, and voice.
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, synchronization cue, 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 forwarded or rewound;
- 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-UAAG10-20020708.
- 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, multimedia player, plug-ins,
documentation, etc.). For each component, the claim must include the following:
- Name and version information for the component. 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").
- Name and version information for the operating environment(s) in
which the component is running.
- Information about which specifications have
been implemented to satisfy the requirements of the document (e.g.,
formats, style sheet languages, APIs, operating environment conventions, etc.)
The information must be sufficient to identify the specification.
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.
- Events label. If the user agent
does not implement these checkpoints related to event handlers, the claim must
say so.
- Selection label. If the user
agent does not implement a selection mechanism, or if
the user agent does not satisfy the requirements associated with the Selection
label, the claim must say so.
- Input modality labels. Each input
modality label ("Pointer" or "Voice") is an assertion that the user agent
satisfies the requirements associated with the label.
- A list of requirements (checkpoints or portions of checkpoints) that the
claimant 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. If a
conformance icon is part of a claim on the Web, it must link to the W3C
explanation of the icon.
A well-formed claim should also include the following information:
- Rationale for any requirements that do not
apply.
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.
Authors of technical specifications (such as W3C Recommendations) should
incorporate the requirements of UAAG 1.0 as part of conformance to their
specifications. This may be done by direct inclusion, or by reference using a
conformance profile. Direct inclusion promotes the integration of specialized
accessibility requirements; inclusion by reference is easier and less prone to
error.
- Identify accessibility features of the specification where they are defined
(see checkpoint
8.1). Optionally, create an appendix of these accessibility features as
well.
- Remember to include user interface requirements as part of conformance to
the specification. Authors of technical specifications tend to focus more on
rendering or other content-related behavior and less on user interface
requirements. UAAG 1.0 makes a number of user interface requirements that
authors will need to consider (such as those in guideline 5 pertaining to viewport behavior).
- Include at least an informative reference to UAAG 1.0 and Techniques for
UAAG 1.0. See the section on how to refer to UAAG
1.0 for more information.
- When a question arises about how a checkpoint applies for a technology,
whether a term is used differently between UAAG 1.0 and the technical
specification, etc. consult the User Agent Accessibility Guidelines Working
Group.
For more information on designing specifications that promote accessibility,
refer to W3C's "XML Accessibility Guidelines" [XAG10].
- Rather than include the generic UAAG 1.0 requirements, tailor them to the
specification. Be specific in the requirements, and include (in context) a
reference to the original UAAG 1.0 checkpoint. The following examples
illustrate what is meant by direct inclusion:
- In an HTML specification, where the
script
,
applet
, and object
elements are defined, include a
statement such as "Per checkpoint 3.4 of UAAG 1.0, a conforming user agent must
allow configuration not to execute scripts, applets, or other executable
content."
- In a CSS specification, where the
'text-decoration'
property
is defined, include a statement such as "A conforming user agent must either:
(a) allow configuration to override the 'blink'
value with the
'none' value, or (b) ignore the 'blink'
value. This is required by
checkpoint 3.3 of UAAG
1.0 [UAAG10]."
Note how these examples refer to the specific elements, attributes, properties,
etc. of the specifications.
- It is better to include some UAAG 1.0 requirements in a specification than
no UAAG 1.0 requirements. However, since UAAG 1.0 requirements are designed to
complement one another, arbitrary selection of requirements may result in
accessibility gaps. Authors are encouraged to include requirements according to
the groups defined by the conformance
labels.
Section G.5 of the SVG 1.0 Recommendation [SVG] states:
Additionally, an authoring tool which is a Conforming SVG Generator conforms
to all of the Priority 1 accessibility guidelines from the document "Authoring
Tool Accessibility Guidelines 1.0" that are relevant to generators of SVG
content.
This statement requires conformance to the Authoring Tool Accessibility
Guidelines as part of conformance to SVG 1.0 (for certain classes of tools).
This type of "conformance requirement by reference" is also possible for UAAG
1.0. However, since conditional
conformance to UAAG 1.0 can vary beyond three conformance levels, it is
important for references to state precisely what is required. This is called a
conformance profile.
This section explains how to create a valid conformance profile to UAAG 1.0.
UAAG 1.0 does not define any (named) conformance profiles, just the mechanism
for creating them.
A valid conformance profile must include the following information:
- The guidelines title/version: "User Agent Accessibility Guidelines
1.0".
- The URI of the guidelines:
http://www.w3.org/WAI/UA/WD-UAAG10-20020708.
- The Conformance level to be satisfied:
"A", "Double-A", or "Triple-A".
- Content type labels. The profile must
include at least one content type label. The requirements associated with that
label must be satisfied as part of conforming to the profile.
- Events label. The profile must
indicate whether the requirements associated with this conformance label
(related to event handlers) are part of conformance to the profile.
- Selection label. The profile
must indicate whether the requirements associated with this conformance label
(related to a selection mechanism) are part of conformance to the profile.
A valid conformance profile should include the following information:
- Applicability: Which checkpoints (or portions of
checkpoints) do not apply for this specification. For instance, if a
specification does not define "tables", the conformance profile should indicate
that checkpoint 10.1 does not
apply. Specification authors should include rationale in their profiles that
explains why a checkpoint does not apply.
A valid conformance profile may include the following information:
- Input modality labels: If conformance
for pointer or voice input is required in addition to keyboard input.
Note: that the following are always required and therefore
need not appear in a conformance profile:
- Keyboard input requirements
- Content focus requirements (only when
the content includes enabled elements; see checkpoint 9.1).
The following is an (partial) example of a valid conformance profile
(expressed in plain text):
As part of conformance to MyFormat 1.0, a user agent must satisfy the
following conformance profile of the "User Agent Accessibility Guidelines 1.0"
[UAAG10]:
- Conformance level A
- Content type labels: Image, Animation, and Video. This means that a
conforming MyFormat user agent must satisfy the requirements associated with
those labels; refer to UAAG 1.0 section 3.5 for details.
- Selection: A conforming MyFormat user agent must implement a text selection
mechanism, and therefore satisfy the requirements associated with the UAAG 1.0
selection label; refer to UAAG 1.0 section 3.7 for details. A conforming
MyFormat user agent is only required to allow users to select text
content.
- Applicability: The following UAAG 1.0 checkpoints do not apply to MyFormat
and therefore do not need to be satisfied for conformance to this
specification:
- 1.2, 3.4, 9.5, 9.6: MyFormat does not allow
inclusion of scripts. Thus, there are no author-supplied event handlers.
- 2.4, 2.6: MyFormat does not
involve synchronization.
- 2.5, 4.6: MyFormat does not
define captions.
- 10.1: MyFormat does not
define tables.
- (And so on)
See the section on how to refer to UAAG 1.0 for
what should appear in the references section of the specification.
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 output 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).
- Audio description
- An audio description (called an "auditory description" in
the Web Content Accessibility Guidelines 1.0 [WCAG10]) 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 audio
description is synchronized with (and possibly included
as part of) the audio track of the presentation, usually
during natural pauses in the audio track. Audio
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 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 superimposed ("on top of") the synchronized visual track.
The term "open captions" generally refers to captions that are always
rendered with a visual track; they cannot be turned off. The term "closed
captions" generally refers to captions that may be turned on and off. The
captions requirements of this document assume that the user agent can recognize the captions as such; see the
section on applicability for more information.
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 audio 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. 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.). The results of "configuration" might
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 terms 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 2.10) 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 audio 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, event type
- User agents often perform a task when an event having a
particular "event type" occurs, including user interface, changes to content,
loading of content, a request from the operating environment, etc.
Some markup languages allow authors to specify that a script, called an event
handler, be executed when an event of a given type 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.
- Focus, content focus, user interface
focus,
current focus
- In this document, the term "content focus" refers to a
user agent mechanism that has 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.
- It has state: the user may "set it" (programmatically or through the user
interface) on an enabled element.
Events may be triggered when the focus is set (or unset). Which events are
triggered depends on the content (e.g., HTML events and CSS pseudo-classes) or
user interface settings.
- Once it has been set, it may be used to trigger other behaviors associated
with the enabled element (e.g., the user may activate a link or change the
state of a form control). These behaviors may be triggered programmatically or
through the user interface (e.g., through 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 set of "bindings" between
user agent functionalities and
user interface input mechanisms (e.g., menus, buttons, keyboard keys, voice
commands, etc.). The default input configuration is the set of bindings 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
- What is identified as "normative" is required for conformance (noting that one may conform in a variety
of well-defined ways to this document). 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. The
point of regard should be available programmatically (e.g., for assistive
technologies).
-
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, and the user may "set it" (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-UAAG10-20020708/.
- 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-UAAG10-20020708/">
"User Agent Accessibility Guidelines 1.0"</a></cite>,
I. Jacobs, J. Gunderson, E. Hansen, eds.,
W3C Working Draft, 8 July 2002.
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.
Other sections of this document explain how to build a conformance claim. Specification authors should also
read the section on designing a UAAG 1.0
conformance profile.
- [CSS1]
- "Cascading
Style Sheets (CSS1) Level 1 Specification", 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]
- "Cascading
Style Sheets, level 2 (CSS2) Specification", 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/.
- [ECMASCRIPT]
- "ECMAScript
Language Specification", European Computer Manufacturers
Association, December 1999. This specification is available at
http://www.ecma.ch/ecma1/STAND/ECMA-262.HTM.
- [INFOSET]
- "XML
Information Set", J. Cowan and R. Tobin, eds., 24 October 2001. This
W3C Recommendation is http://www.w3.org/TR/2001/REC-xml-infoset-20011024/.
- [JAVA]
- "The Java Language
Specification", Sun Microsystems Inc., J. Gosling, B. Joy, and G.
Steele, September 1996. The specification is available at
http://java.sun.com/docs/books/jls.
- [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.,
30 April 2002. This W3C Working Draft is
http://www.w3.org/TR/2002/WD-charmod-20020430/. The latest version is available at
http://www.w3.org/TR/charmod/.
- [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/.
- [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., 7 August 2001. This W3C Recommendation is
http://www.w3.org/TR/2001/REC-smil20-20010807/.
- [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 3.2". This technical report of the Unicode Consortium is available at
http://www.unicode.org/unicode/reports/tr28/. 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]
-
"Introduction and Overview of W3C Speech Interface Framework", J.
Larson, 4 December 2000. This W3C Working Draft is
http://www.w3.org/TR/2000/WD-voice-intro-20001204/. The latest version is available at
http://www.w3.org/TR/voice-intro. This document includes references to
additional W3C specifications about voice browser technology.
- [W3CPROCESS]
- "World Wide
Web Consortium Process Document", I. Jacobs ed. The 19 July 2001
version of the Process Document is
http://www.w3.org/Consortium/Process-20010719/. The latest version is available at
http://www.w3.org/Consortium/Process/.
-
[WCAG10-TECHS]
- "Techniques for Web
Content Accessibility Guidelines 1.0", W. Chisholm, G. Vanderheiden,
and I. Jacobs, eds., 6 November 2000. This W3C Note is
http://www.w3.org/TR/1999/WAI-WEBCONTENT-TECHS-19990505/. The latest version is available at
http://www.w3.org/TR/WCAG10-TECHS/. Additional format-specific techniques
documents are available from this Note.
- [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.
- [XAG10]
- "XML
Accessibility Guidelines 1.0", D. Dardailler, S. Palmer, eds., 29
August 2001. This W3C Working Draft is
http://www.w3.org/TR/2001/WD-xmlgl-20010829. The latest version is available at
http://www.w3.org/TR/xmlgl.
- [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.
- [XMLDSIG]
-
"XML-Signature Syntax and Processing", D. Eastlake, J. Reagle, D.
Solo, eds., 12 February 2002. This W3C Recommendation is
http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/.
- [XMLENC]
- "XML
Encryption Syntax and Processing", D. Eastlake, J. Reagle, eds., 4
March 2002. This W3C Candidate Recommendation is
http://www.w3.org/TR/2002/CR-xmlenc-core-20020304/. The latest version is available at
http://www.w3.org/TR/xmlenc-core/.
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, Jonny Axelsson, 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, Dirk Mueller, 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.