Editing Styles:
- changed-from-version1: Any text that has changed since version 1.0 except new changes.
- newly-approved-text: New changes to this draft
- proposed-text: Proposals that have not been accepted
- @@editor-notes@@: Notices from the editor(s).
Ensure that the user can interact with the
user agent (and the content it renders) through
different input and output devices.
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 (e.g., keyboard,
pointing device, and voice input) and output modalities (e.g.,
graphical, speech, or braille
rendering).
Enabling full user agent operation through
the keyboard is an important part of promoting device-independence in
target user agents. In addition to the fact
that most operating environments include support for some form of keyboard,
the reasons for this include:
- 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 generally makes fewer perceptual/motor demands for moving
the pointing device to a visual target.
- 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, or as braille.
The API requirements of guideline 6 also promote device independence by ensuring
communication with other software, including assistive technologies.
@@7.2, 7.4 Possibly move here@@
@@CL: "Precedence of 'operations' - keys"
Level A Success Criteria for Guideline 1.1
- 1.1.1 Keyboard (user interface "chrome", content display): The user must be
able, through keyboard input alone, to navigate to and operate all of the functions included in the user interface (e.g., navigating and selecting and content within views, operating the user interface "chrome", installing
and configuring the tool, and accessing documentation), except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints (e.g. freeform drawing). This applies to at least one mechanism per @@browsing outcome@@, allowing
non-keyboard accessible mechanisms to remain available (e.g.,
providing resizing with mouse-"handles" and with keystrokes).[ATAG 2.0]
- 1.1.2 Separate Activation (user interface "chrome", content display): The user must have
the option to have selection separate from activation
(e.g., navigating through the items in a dropdown menu without
activating any of the items).[ATAG 2.0]
- Provide a configuration to have the keyboard controls of the user agent interface "chrome" override any conflicting keyboard controls in the rendered content.
- 1.1.3 Available Keystrokes (user interface "chrome", content display): The user must be able to determine currently available
keystrokes at
all times (e.g., from a central location such as a list in the
help system or a distributed location such as associating shortcuts
with menu items).[ATAG 2.0]
- 1.1.4 Standard Text Area Conventions (content
display): Views that render text must support the standard text area conventions for
the platform including, but not necessarily limited to:
character keys, backspace/delete, insert, "arrow" key
navigation, page up/page down, navigate to start/end, navigate
by paragraph, shift-to-select mechanism, etc.[ATAG 2.0]
- 1.1.5 "Chrome" Navigation (user interface "chrome"): Authors must be able to use the keyboard to traverse all of the controls forwards and backwards, including controls in floating toolbars, panels, etc. using conventions of the platform (e.g., via "tab", "shift-tab", "ctrl-tab", "ctrl-shift-tab").[ATAG 2.0]
- Provide information to the user about current user preferences for input configurations.
Level AA Success Criteria for Guideline A.3.1
- 1.1.6 Accelerator Keys (user interface "chrome"): If any of the following functionalities are implemented by the
authoring tool, the author must have the option to enable
key-plus-modifier-key (or single-key) access to them:
[ATAG 2.0]
- (a) move content focus to the next/previous enabled element in document order,
- (b) activate the link designated by the content focus,
- (c) open find function,
- (d) increase/decrease the scale of rendered text,
- (e) increase/decrease global volume,
- (f) stop/pause/resume audio and animations, including video and animated images,
- (g) next/previous history state (forward/back),
- (h) enter a URI for a new resource,
- (i) add a URI to favorites (i.e., bookmarked resources),
- (j) view favorites,
- (k) reload a resource, and
- (l) interrupt a request to load or reload a resource.
- Allow the user to override any binding that is part of the user agent default input configuration.
- Provide a feature that displays author-defined keyboard bindings that are known to the user agent.
- 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.
Level AAA Success Criteria for Guideline A.3.1
- 1.1.7 Intergroup Navigation (user interface "chrome", content
display): If logical groups of focusable controls (e.g., toolbars, dialogs, labeled groups, panels) are present, authors must be able to use the keyboard to navigate to a focusable control in the next and previous groups.[ATAG 2.0]
- 1.1.8 Group Navigation (user interface "chrome", content
display): If logical groups of focusable controls are present, authors must be able to use the keyboard to navigate to the first, last, next and previous focusable controls in the current group.[ATAG 2.0]
Level A Success Criteria for Guideline 1.X
- Ensure that the user can operate,
through keyboard input alone, any user agent functionality available through
the user
interface.
- If a keystroke is not defined by the user agent user interface,the user agent should pass it on to the user agent extensions, HTML elements, then JavaScript functions, in that order. (@@JA: binary choice between UA user interface grabs first and doc grabs first@@)
- Provide information to the user about
current user preferences for input configurations. (@@11.1@@)
- Follow operating environment conventions for keyboard selection. (@@broken out from 7.1@@)
Level AA Success Criteria for Guideline 1.X
- Allow the user to override any binding that is part of the
user agent default input configuration. (@@11.3@@)
- Provide a feature that displays author-defined keyboard bindings that are known to the user agent. (@@reword of 11.2@@)
- 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.(@@11.4@@)
- 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.(@@11.4@@)
- Provide documentation of the default user agent input
configuration (e.g., the default keyboard bindings).(@@12.3@@)
- Establish and document how the user agent resolves key binding conflicts between the user agent user interface, user agent extensions (e.g plug-ins), HTML elements (i.e. accesskeys), and JavaScript functions (i.e. keypress events).
- Ensure that the user agent default input
configuration includes bindings for the following functionalities required
by other checkpoints in this document(@@11.5@@)
:
- move content focus to the
next enabled element in
document order, and move content focus to the previous enabled
element in document order (checkpoints 9.3 and 9.7);
- activate the link designated by the content focus (checkpoints 1.1 and 9.1);
- search for text, search again for same text (checkpoint 9.8);
- increase the scale of rendered text, and decrease the scale
of rendered text (checkpoint 4.1);
- increase global volume, and decrease global volume (checkpoint 4.7); and
- stop, pause, resume, and navigate efficiently selected audio and animations, including video and animated
images (checkpoint 4.5).
- If the user agent supports the following functionalities, the
default input configuration must also include bindings for them(@@11.5@@) :
- next history state (forward), and previous history state (back);
- enter a URI for a new resource;
- add a URI to favorites (i.e., bookmarked resources);
- view favorites;
- reload a resource;
- interrupt a request to load or reload a resource;
- for graphical viewports: navigate forward and backward through rendered
content by approximately the height of the viewport; and
- for user agents that render content in lines of (at least) text: move the
point of regard to the next and previous line.
Level AAA Success Criteria for Guideline 1.X
Note: For example, ensure that the user can interact with
enabled elements, select content,
navigate viewports, configure the user agent, access documentation, install the
user agent, and operate user interface controls, all
entirely through keyboard input.
User agents generally support at least three types of keyboard
operation:
- Direct (e.g., keyboard shortcuts such as "F1" to open the help menu; see
checkpoint 11.4 for single-key
access requirements),
- Sequential
(e.g., navigation through cascading menus), and
- Spatial (e.g., when the keyboard is used to move the pointing device in
two-dimensional visual space to
manipulate a bitmap image).
User agents should support direct or sequential keyboard operation for all
functionalities. Furthermore, the user agent should satisfy this checkpoint by
offering a combination of keyboard-operable user interface controls (e.g.,
keyboard operable print menus and settings) and direct keyboard shortcuts
(e.g., to print the current page).
It is also possible to claim
conformance to this document for
full support through pointing device input and/or voice input. See the section
on Input modality
labels.
Level A Success Criteria for Guideline 1.2
- Allow the user to activate, through keyboard input alone, all
input device event handlers that are
explicitly associated with the element designated by the content focus.
- 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. @@moved from 9.5@@
- 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.@@moved from 9.6@@
- In order to satisfy provision one
of this checkpoint, the user must be able to activate as a group all event
handlers of the same input device event type. For example, if there are 10
handlers associated with the
onmousedown
event type, the user must
be able to activate the entire group of 10 through keyboard input alone, and
must not be required to activate each handler separately.
Level AA Success Criteria for Guideline 1.2
- (No level AA success criteria for Guideline 1.2)
Level AAA Success Criteria for Guideline 1.2
- (No level AAA success criteria for Guideline 1.2)
- Provision one of this checkpoint applies to handlers of any input
device event type, including event types for keyboard, pointing device, and
voice input.
- 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.
- This checkpoint is mutually exclusive of
checkpoint 1.1 since
the current checkpoint may be excluded from a
conformance profile, unlike
other keyboard operation requirements.
- Conformance
profile labels:
Events
Note: Refer to the checkpoints of guideline 9 for more information about focus
requirements.
Level A Success Criteria for Guideline 1.3
Level AA Success Criteria for Guideline 1.3
- (No level AA success criteria for Guideline 1.3)
Level AAA Success Criteria for Guideline 1.3
- (No level AAA success criteria for Guideline 1.3)
Note: For example, if the user is alerted of an event by an
audio cue, a visually-rendered text equivalent in the status bar could satisfy
this checkpoint. Per checkpoint
6.5, 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. Examples of priority properties for a text message are off (not currently live), polite (low priority), assertive (medium priority), and rude (high priority) for AJAX live regions.
Ensure that users have access to all content,
notably conditional
content that may have been provided to meet the requirements of the Web
Content Accessibility Guidelines 2.0 [WCAG20].
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, in order to find necessary information, the user
may have to look at Uniform Resource Identifiers (URIs) for
information, HTML comments, XML element
names, or script data.
- Configuration and control of rendering are important for access. For
instance, 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 might otherwise be impossible.
Authors may use the conditional content mechanisms of
a specification to satisfy the requirements of the Web Content Accessibility
Guidelines 2.0 [WCAG20]. 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 a configuration preference (e.g., they have a slow
Internet connection and prefer not to download movies or images).
- Render content according to format specification
(e.g., for a markup language or style sheet language).
- 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 UAAG 1.0, the user agent may disregard the rendering requirement
of the other specification and still satisfy this checkpoint; see the section
on the relation of this document to general
software design guidelines and other specifications for more
information.
- The user agent is not required to satisfy this checkpoint for all
implemented specifications; see the section on
conformance profiles for
more information.
- This checkpoint excludes the requirements of
checkpoint
2.6.
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 or by saving it to disk).
- 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, or
- any media object identified by Internet media type to be an XML document
(as defined in [XML], section 2) or SGML application.
Refer, for example, to Internet media types defined in "XML Media Types"
[RFC3023].
- 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 profiles for
more information. However, user agents should provide a text view for all
implemented text formats.
Level A Success Criteria for Guideline 2.3
- 2.3.1 Browse and Render: The user can browse and have rendered any items in a conditional content stack that are encoded in technologies that the user agent supports.
- 2.3.2 Configurable Dimensions: If the dimensions of the items in the conditional content stack differ, then a configuration should control whether the dimensions of the default item or the rendered item are used.
- 2.3.3 Available Programmatically: If an item in the conditional content stack is plain text (e.g. alt text) then it is available programmatically even when not on-screen.
- 2.3.4 Simultaneous Rendering: Previously rendered items can continue to be rendered alongside other items the user requests from the conditional content stack unless the user agent can recognize a mutual exclusion (e.g. conflicting soundtracks).
Level AA Success Criteria for Guideline 2.3
- 2.3.5 Configurable Default Rendering: The user can set preferences for which items in a conditional content stack are rendered by default.
- 2.3.6 Alert to Non-Rendered: The user is alerted to the presence of non-rendered items in the conditional content stack that are encoded in technologies that the user agent supports.
Level AAA Success Criteria for Guideline 2.3
- (No level AAA success criteria for Guideline 2.3)
- To satisfy provision one of this checkpoint, 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 of this checkpoint, the user agent may provide
access on a per-element basis (e.g., by allowing the user to query individual
elements) or for all elements (e.g., by offering a configuration to render
conditional content all the time).
- To satisfy the requirement of provision two of this checkpoint to allow the
user to view the content associated with each placeholder, the user agent may either
render the associated content in a separate viewport or in place of the
placeholder.
- For the placeholder requirement of
provision two of this checkpoint, a request to view the original content
associated with a placeholder is considered
an explicit user request to render
that content.
- The user agent is not required to include placeholders in the
document object. A placeholder that
is part of the document object should conform to the Web Content Accessibility
Guidelines 2.0 [WCAG20]. 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).
- Conformance detail: For all
content
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). User agents should expose configuration choices in as highly visible a fashion as is practical such as on a menu entry or dialog settings devoted to accessibility.
- 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.
- The user agent may satisfy this checkpoint by pausing processing
automatically to allow for user input, and resuming processing on
explicit user request. When
using this technique, 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 (or, "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.
- 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 3.4, which involves client-driven content
retrieval.
- Allow configuration or control to render text transcripts,
collated text
transcripts, captions, and
audio descriptions
in content at the same time as the associated
audio tracks and visual tracks.
- Respect synchronization cues (e.g., in markup)
during rendering.
-
Allow configuration to generate
repair text when the user agent
recognizes that the author has not provided
conditional
content required by the format specification.
- The user agent may satisfy this checkpoint by basing the repair text on any
of the following available sources of information: URI reference (as defined in
[RFC2396], section 4), 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 content:
Note: In some authoring scenarios, empty content (e.g.,
alt=""
in HTML) 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 does not make sense out of the mosaic. Refer to the Web
Content Accessibility Guidelines 2.0 [WCAG20] for more information about
text equivalents.
- Allow configuration to render all
conditional
content automatically.
- As part of satisfying provision
one of this checkpoint, provide access according to specification, or where
unspecified, by applying one of the techniques 1a, 2a, or 1b defined in
provision two of checkpoint
2.3.
- The user agent may satisfy provision one of this checkpoint through
multiple configurations (e.g., a first configuration to render one type of
conditional content automatically and a second to render another
type).
- The user agent is not required to render all conditional content at the
same time in a single viewport.
- Conformance detail: 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).
- For graphical user agents, allow
configuration not to render
text in unsupported scripts (i.e.,
writing systems) when that text would
otherwise be rendered.
- When configured per provision one
of this checkpoint, indicate to the user in context that author-supplied
content has not been rendered due to lack of support for a writing
system.
- This checkpoint does not require the user agent to allow different
configurations for different writing systems.
Note: The primary purpose of this checkpoint is to benefit
users with serial access to content
or who navigate
sequentially, allowing them to skip portions of content that would be
unusable if rendered graphically as "garbage."
Ensure that the user may turn off rendering of
content (e.g., audio, video, scripts) that may reduce accessibility by
obscuring other content or disorienting the user.
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 (e.g., viewports that open without notice or
automatic content retrieval) 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.
- Allow configuration not to render images that are rendered on the base background.
- Allowing users to turn off images that the user agent would render on the base background.
- This checkpoint must be satisfied for all implemented image specifications; see the
section on conformance
profiles.
- When configured not to render background images, the user agent is not
required to retrieve them until the user requests them explicitly. When
background images are not rendered, user agents should render a solid
background color instead; see checkpoint 4.3 for information about text colors.
- This checkpoint only requires control of background images for
"two-layered" renderings, where the background is considered the first layer
and everything rendered above it is considered the second layer.
- Conformance
profile labels:
Image
Note: When background images are not rendered, they are
considered conditional
content. See checkpoint
2.3 for information about providing access to conditional content.
3.2 Toggle audio, video, animated images, and animated/blinking text (P1)
Techniques for checkpoint 3.2
- Allow configuration not to render audio, video,
or animated image content, except on
explicit user
request.
- Allow configuration to render animated or blinking text content as motionless, unblinking text.
- The user agent may satisfy the first success criteria by making video and animated
images invisible and audio silent, but this technique is not
recommended.
- The user agent may satisfy the second success criteria by showing still images in place of video and image animations. @@Still issues with this@@
- The user must still have access to all animated/blinking text content, but the user agent may render it in a separate viewport (e.g., for
large amounts of streaming text).
- The user agent may satisfy the second success criteria by always
rendering animated or blinking text as motionless, unblinking
text.
- This checkpoint does not apply for content the user agent cannot deterministically recognize as audio, video, animated images, or animated/blinking text.
- 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 implemented audio, video, and animated
image specifications; see the section on
conformance profiles.
- 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.
- Checkpoint 4.3 addresses user control of blinking effects caused by rapid color changes.
- Conformance
profile labels: VisualText, Animation,
Video,
Audio
Note: See guideline 4 for additional requirements related to the
control of rendered audio, video, and animated images. When these content types
are not rendered, they are considered conditional content. See
checkpoint 2.3 for
information about providing access to conditional content. 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, objects and applets).
- Provide the user with the ability to toggle whether the base user agent executes content that it is able to . - if cond. content exists reveal it (2.3)
- Provide the user with the ability to toggle the loading of plugins that execute content the base browser is unable to execute - if cond. content exists reveal it (2.3)
Note: Executable content may provide very useful
functionality, not all of which causes accessibility problems. If content is not executed it is important to instead render any conditional content that the author may provide.@@take another look at this@@
- Allow configuration so that the user agent only
retrieves content on
explicit user
request.
- When the user chooses not to retrieve (fresh) content, the user agent may
ignore that content; buffering is not required.
- This checkpoint only applies when the user agent (not the server)
automatically initiates the request for fresh content. However, 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, and is replaced by content that results from a second
request.
Note: For example, if the user agent supports automatic
content retrieval, to ensure that the user does not become disoriented by
sudden automatic changes, allow configurations such as "Never retrieve content
automatically" and "Require confirmation before content retrieval."
- Allow configuration not to render image
content.
- The user agent may satisfy this checkpoint by making images
invisible, but this
technique is not recommended.
Note: When images are not rendered, they are considered
conditional
content. See checkpoint
2.3 for information about providing access to conditional content.
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
Ensure that the user can select preferred
styles (e.g., colors, size of rendered text, and synthesized speech
characteristics) from choices offered by the user agent. Allow the user to
override author-specified styles
and user agent
default styles.
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, some
users 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.
- Allow global configuration of the
scale of visually rendered text content. Preserve
distinctions in the size of rendered text as the user increases or decreases
the scale.
- As part of satisfying provision one of
this checkpoint, provide a configuration option to override rendered text sizes specified by
the author or user agent defaults.
- As part of satisfying provision one of
this checkpoint, 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.
- 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.
- The word "scale" is used in this checkpoint to mean the general size of
text.
- The user agent is not required to satisfy this requirement through
proportional scaling. What must hold is that if rendered text A is smaller than
rendered text B at one value of the configuration setting of provision one,
then text A will still be smaller than text B at another value of this
configuration setting.
- Conformance
profile labels:
VisualText
- Allow global configuration of the font
family of all visually rendered text content.
- As part of satisfying provision one of
this checkpoint, provide a configuration option to override font families specified by the
author or by user agent defaults.
- As part of satisfying provision one of
this checkpoint, 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.
- For text that cannot be rendered properly using the
user's preferred font family, the user agent should 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 content.
- As part of satisfying provision one of
this checkpoint, provide a configuration option to override foreground and background colors
specified by the author or user agent defaults.
- As part of satisfying provision one of
this checkpoint, 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.
Note: User configuration of foreground and background
colors may inadvertently lead to the inability to distinguish ordinary text
from selected text or focused text. See checkpoint 10.2 for more information about highlight
styles.
- Allow the user to slow the presentation rate
of rendered audio and animation content (including video and
animated images).
- As part of satisfying provision one of this
checkpoint, for a visual track, provide at
least one setting between 40% and 60% of the original speed.
- As part of satisfying provision one of this
checkpoint, 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.
- 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
profile 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 2.0" [WCAG20] not to convey information
through style alone (e.g., through color alone or style sheets alone). @@RE-LOOK AT THIS NOTE@@
- Allow the user to stop, pause, and resume
rendered audio and animation content (including
video and animated images) that last three or more seconds at their default
playback rate.
- Allow the user to navigate efficiently
within rendered audio and animations (including video and animated
images) that last three or more seconds at their default playback
rate.
- The user agent may satisfy the navigation requirement of provision two of
this checkpoint through forward and backward serial access techniques (e.g., advance
five seconds), or direct access techniques (e.g., start playing at the
10-minute mark), or some combination.
- When using serial access techniques
to satisfy provision two of this checkpoint, the user agent is not required to
play back content during 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
profile labels:
Animation,
Audio
Note: The lower bound of three seconds is part of this
checkpoint since control is not required for brief audio and animation content,
such as short clips or beeps. Respect synchronization cues per
checkpoint 2.6.
- For graphical viewports, allow configuration so
that captions synchronized with a
visual track in content are not obscured
by it.
- 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.
- Allow global configuration of the
volume of all rendered audio.
- As part of satisfying provision one of
this checkpoint, allow the user to choose zero volume (i.e.,
silent).
Note: User agents should allow configuration of volume
through available operating environment
mechanisms.
- Allow independent
control of the volumes of rendered
audio content synchronized to play
simultaneously.
- 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
profile 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.
- Allow configuration of the synthesized speech
rate, according to the full range offered by the speech synthesizer.
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.
Note: See checkpoint 4.8 for information about independent volume
control of different sources of audio.
- Allow configuration of synthesized speech
characteristics according to the full range of values offered by the speech
synthesizer.
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: voice (e.g., adult male voice, female
child voice, robot voice), pitch, and stress. 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.
Note: This checkpoint is more specific than
checkpoint
4.11. It requires support for the voice characteristics listed in the
provisions of this checkpoint. Definitions for these characteristics are based
on descriptions in section 19 of the Cascading Style Sheets Level 2
Recommendation [CSS2]; 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, for example, by choosing from
present options distinguished by gender, age, or accent. 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.
Note: Definitions for the functionalities listed in the
provisions of this checkpoint are based on descriptions in section 19 of the
Cascading Style Sheets Level 2 Recommendation
[CSS2]; refer to that specification
for additional informative
descriptions.
- 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 turn off (i.e., ignore)
author and user style sheets.
- 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.
Ensure that the user can control the behavior
of viewports and user interface controls, including those that may be
manipulated by the author (e.g., through scripts).
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, or which viewport has
the current focus. 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.
Guideline: 5.X Manage viewport opening
Level A Success Criteria for Guideline 5.X
Level AA Success Criteria for Guideline 5.X
- Allow configuration so that "top-level" viewports (defn: viewports that are not contained within other user agent viewports) only open
on explicit user request.
- When configured to open "top-level" viewports only on explicit user request, instead of opening a viewport automatically, alert the user and
allow the user to open it with an explicit request (e.g., by
confirming a prompt or following a link generated by the user agent).
- When configured to allow "top-level" viewports to open without explicit user request, allow configuration so that if a "top-level" viewport opens, neither
its content focus nor its user interface focus automatically becomes the current focus.
- Allow configuration so that the viewport with the current focus remains "on top" of all
other viewports with which it overlaps.
- Allow the user to close any "top-level" viewport.
- Ensure that when a viewport's selection changes, it is at least
partially in the viewport after the
change.
- Ensure that when a viewport's content focus changes, it is at least
partially in the viewport after the
change.
- Allow configuration so that all viewports follow the same user interface configuration as the current or spawning viewport, including chrome.
- Allow configuration to make graphical viewports resizable
- Graphical viewports must include scrollbars if the rendered content (including after user preferences have been applied) extends beyond the viewport dimensions
- "Top-level" viewports must include close mechanisms.
Level AAA Success Criteria for Guideline 5.X
- Allow configuration so that if a
viewport opens without
explicit user request, neither
its content focus nor its
user interface focus
automatically becomes the current focus.
- To satisfy provision one of this checkpoint, 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 of this
checkpoint, instead of opening a viewport automatically, alert the user and
allow the user to open it with an explicit request (e.g., by
confirming a prompt or following a link generated by the user agent).
- Allow the user to close viewports.
- To satisfy provision one of this checkpoint, configuration is preferred,
but is not required if viewports can only ever open on explicit user
request.
- If a viewport (e.g., a frame set) contains other viewports, the provisions
of this checkpoint 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.
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.
- Configuration is preferred, but is 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 (e.g., via the pointing device), submission when the user has
interacted with all form controls, and submission when an
onmouseover
or onchange
event
occurs.
Implement interoperable interfaces to
communicate with other software (e.g., assistive technologies, the operating
environment, and plug-ins).
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.
- 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 the state or value of a
piece of HTML or XML content through the user interface (e.g., by checking a
box or editing a text area), allow programmatic read access to the current
state or value, and allow the same degree of write access programmatically as
is available through the user interface.
- Provide access to the content required in
checkpoint 6.1 by conforming
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 of this
checkpoint:
- In the Java and ECMAScript operating environments, export the normative
bindings specified in the DOM Level 2 Core Specification
[DOM2CORE], or
- In other operating environments, the exported bindings (e.g., C++) must be
publicly documented.
- Refer to the "Document Object Model (DOM) Level 2 Core Specification"
[DOM2CORE] for information about
which versions of HTML, XML, Java, and
ECMAScript are covered.
Appendix
D contains the Java bindings and
Appendix E contains the ECMAScript bindings.
- The user agent is not required to export the bindings outside of the user
agent process (though doing so may be useful to assistive technology
developers).
Note: This checkpoint stands apart from
checkpoint 6.1 to emphasize
the distinction between what information is required and how to provide access
to that information. Furthermore, the DOM Level 2 Core Specification does not
provide access to current states and values referred to in provision three of
checkpoint 6.1. For HTML
content, the interfaces defined in [DOM2HTML] do provide access to
current states and values.
- For content other than HTML
and XML, provide structured programmatic read access to
content.
- If the user can modify the state or value
of a piece of non-HTML/XML content through the user interface (e.g., by checking a
box or editing a text area), allow programmatic read access to the current
state or value, and allow the same degree of write access programmatically as
is available through the user interface.
- As part of satisfying provision one of this
checkpoint, 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,
- "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
checkpoints 6.1 and
6.2.
- For graphical user agents, make available
bounding dimensions and coordinates of rendered graphical objects. Coordinates
must be relative to the point of origin in the graphical environment (e.g.,
with respect to the desktop), not the viewport.
- For graphical user agents, provide access
to the following information about each piece of rendered text: font family,
font size, and foreground and background colors.
- As part of satisfying provisions one and
two of this checkpoint, implement at least one API according to the API cascade
described in provision two of checkpoint 6.3.
Note: User agents should provide programmatic access to
additional useful information about rendered content that is not available
through the APIs required by checkpoints 6.2 and 6.3, including the correspondence (in both directions)
between graphical objects and their source in the document object, and information
about the role of each graphical object.
- Provide programmatic read access to
user agent user interface
controls, selection,
content focus, and
user interface focus.
- If the user can modify the state or value of a
user agent user interface
control (e.g., by checking a box or editing a text area), allow
programmatic read access to the current state or value, and allow the same
degree of write access programmatically as is available through the user
interface.
- As part of satisfying provisions one and two of
this checkpoint, implement at least one API according to the API cascade
described in provision two of checkpoint 6.3.
Note: APIs used to satisfy the requirements of this
checkpoint may vary. For instance, they may be independent of a particular
operating environment (e.g., the W3C DOM), or the conventional APIs for a
particular operating environment, or the conventional APIs for programming
languages, plug-ins, or virtual machine
environments. User agent developers are encouraged to implement APIs that allow
assistive technologies to interoperate with multiple types of software in a
given operating environment (e.g., user agents, word processors, and
spreadsheet programs), 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, states and values of content,
user agent user interface controls,
selection, content focus, and
user interface focus.
- As part of satisfying provision one of this
checkpoint, implement at least one API according to the API cascade of
provision two of checkpoint
6.3.
Note: For instance, provide programmatic notification when
user interaction in one frame causes automatic changes to content in
another.
-
Implement
APIs for the keyboard (@@better defn needed@@) 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 stage.
- For an API implemented to satisfy
requirements of this document, support the character encodings required for
that API.
Note: Support for character encodings is an important part
of ensuring that text is correctly 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.
- 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 of this
checkpoint:
- In the Java and ECMAScript operating environments, export the normative
bindings specified in the CSS module of the DOM Level 2
Style Specification
[DOM2STYLE], or
- In other operating environments, the exported bindings (e.g., C++) must be
publicly documented.
- For the purposes of satisfying this checkpoint, Cascading Style Sheets
(CSS) are defined by either CSS Level 1
[CSS1] or CSS Level 2
[CSS2].
- Refer to the "Document Object Model (DOM) Level 2 Style Specification"
[DOM2STYLE] for information
about which versions of Java and ECMAScript are covered.
Appendix B contains the Java bindings and
Appendix C contains the ECMAScript bindings.
- The user agent is not required to export the bindings outside of the user
agent process.
- 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.
Observe operating environment conventions for the
user agent user interface,
documentation, input configurations, and installation.
Part of user agent accessibility involves following the conventions of the
user's operating environment, including:
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, and documentation. 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.
7.X Observe operating environment conventions (@@Guideline A.1.3@@)
Level A Success Criteria for Guideline 7.X
Level AA Success Criteria for Guideline 7.X
Level AAA Success Criteria for Guideline 7.X
Follow operating environment
conventions that benefit accessibility when implementing the selection, content focus, and
user interface focus.
Note: See checkpoints 9.1 and 9.2
for more information about content focus and user interface focus.
Ensure that default
input
configurations of the user agent do not interfere with
operating
environment accessibility conventions (e.g., for keyboard
accessibility, speech commands).
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.
- 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 2.0"
[WCAG20] or of the current
document.
- This checkpoint excludes the requirements of checkpoints
7.1 and
7.4.
- Conformance detail: For user agent
features
Note: Some of these conventions (e.g., sticky keys, mouse
keys, and show sounds) 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. See checkpoint 11.5 for information about the user agent's
default input configuration.
Support the accessibility features of
all implemented specifications. Implement W3C Recommendations when available
and appropriate for a task.
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.
- Implement the accessibility features of
specifications (e.g., markup languages, style sheet languages, metadata
languages, and graphics formats).
- 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 2.0"
[WCAG20].
- The user agent is not required to satisfy this checkpoint for all
implemented specifications; see the section on
conformance profiles for
more information.
- Conformance detail: 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 2.0
[WCAG20].@@consider ATAG 2.0 "Benchmarked Technologies"@@
- When a requirement of another specification contradicts a requirement of
the current document, the user agent may disregard the requirement of the other
specification and still satisfy this checkpoint.
- A specification is considered "available" if it is published (e.g., as a
W3C Recommendation) in time for integration into a user agent's development
cycle.
- The user agent is not required to satisfy this checkpoint for all
implemented specifications; see the section on
conformance profiles for
more information.
- Conformance detail: For all
content
Note: For instance, for markup, the user agent may
conform to HTML 4
[HTML4], XHTML 1.0
[XHTML10], and/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].
Provide
access to content through a variety of navigation mechanisms, including
sequential navigation, direct navigation, searches, and structured
navigation.
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 with serial access to content
or who navigate
sequentially (by moving the focus).
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) and to users with visual disabilities. Expert users also
benefit from direct navigation. 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,
such as blocks of content, headers and sections, tables, forms and form
elements, enabled elements, navigation mechanisms, and containers. 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).
9.X Focus Management
Level A Success Criteria for Guideline 9.X
- Provide at least one content focus for each viewport (including frames) where enabled elements are part of the rendered
content. (@@from 9.1@@)
- Allow the user to make the content focus of
each viewport the current focus. (@@from 9.1@@)
- Provide a user interface
focus.(@@from 9.2@@)
- Ensure user interface focus for extensions to the user interface (chrome). (@@If it knows how to insert and render the extension in its chrome, then it should have good enough programmatic access and knowledge to properly give focus. - Tech XUL spec for FF@@)
- User agent is responsible for notifying any nested user agent that focus should move into it
- User agents must be able to escape focus from a nested viewport (including nested viewports that are user agents) @@techs: compound docs?@@
- Embedded user agents are responsible for notifying embedding user agent that focus should move back to it. @@Embedded user agents must write to AccessAPI and HTML DOM if applicable@@
- Allow the user to move the content focus forward or backward to any enabled element in the viewport.(@@from 9.3@@)
- If
the author has not specified a navigation order, allow at least forward sequential
navigation, in document order, to any enabled element in the viewport.(@@from 9.3@@)
- Allow configuration so that the content focus of
a viewport only changes on explicit user request.(@@from 9.3@@)
- Allow configuration so that moving the content focus to or from an enabled element does cause the user agent to take any further action.(@@9.5@@)
- Follow operating environment conventions that benefit accessibility when implementing content focus and user interface focus.(@@from 7.1@@)
Level AA Success Criteria for Guideline 9.X
Level AAA Success Criteria for Guideline 9.X
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.
- When a viewport includes no enabled elements (either because the format
does not provide for this, or a given piece of content has no enabled
elements), the content focus requirements of the following checkpoints do not
apply: 1.2,
5.1,
5.4,
6.6,
7.1,
9.3,
9.4,
9.5,
9.6,
9.7,
10.2, and
11.5.
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.
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 of this checkpoint.
- To satisfy provision two of this checkpoint, configuration is preferred,
but is not required if the content focus only ever changes on
explicit user
request.
Note: In addition to forward sequential navigation, the
user agent should also allow reverse sequential navigation. See
checkpoint 9.9 for information
about structured navigation. See checkpoints
5.1 and
6.6 for more information
about focus changes.
- If the user agent maintains a viewport history mechanism (e.g., via the "back button") that stores previous "viable" states (i.e., that have not been negated by the content, user agent settings or user agent extensions) it must maintain
information about the point of regard and it must restore the saved values when the user returns to a state in the history.
- 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
profile 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.
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.
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 sequential
navigation order described in checkpoint 9.3. See
checkpoint 1.2
for information about activation of event handlers associated with the element
with focus.
Extend the functionality required in provision
three of checkpoint 9.3 by
allowing the same sequential navigation in
reverse document order.
As part of satisfying provision one of this
checkpoint, the user agent must not include disabled elements in the navigation
order.
-
Allow the user to search within rendered (e.g., not hidden with a style) content for text and text alternatives for a sequence
of characters from the document character set.
-
Allow the user to start a forward or backward 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 at least partially
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 or after the last match in content (i.e.,
prior to starting the search over from the beginning of content).
-
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.
- Provide efficient navigation over important structural elements in rendered content.
- As part of satisfying provision one of this
checkpoint, 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., sequential
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 and attributes identified for checkpoints
9.9 and
10.4.
- As part of satisfying provision one of
this checkpoint, 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, or to navigate within and among tables and table cells.
Provide information that will help the user
understand browsing context.
All users require clues to help them understand their "location" when
browsing: where they are, how they got there, where they can go, and what's
nearby. 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, and the title of the current document or
frame.
- information about specific elements, such as the dimensions of a table, the
length of an audio clip, and the structure of a form.
- 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 with
serial access to content or who
navigate
sequentially. For instance, some users cannot scan a graphically displayed
table with their eyes for information about a table cell's headers or
neighboring cells. User agents need to provide other means for users to
understand, for example, table cell relationships, frame relationships (what
relationship does the graphical layout convey?), form context (have I filled
out the form completely?), and link information (have I already visited this
link?).
- For graphical user agents that render tables,
for each table cell, allow the user to view associated header
information.
- The user agent may satisfy this checkpoint by allowing the user to query
each table cell for associated header information.
- The user agent may satisfy this checkpoint by rendering the table cell and
associated header information so they are both visible in the same
viewport.
- 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 of this checkpoint, 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 of this checkpoint, 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 three of
checkpoint 4.1.
- for font family, the range required by provision three 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.
Note: Examples of highlight mechanisms for selection and
content focus include foreground and background color variations, underlining,
border styling, and distinctive synthesized speech prosody. 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.
- Extend the functionality required by
provision two of checkpoint 10.2 by allowing configuration through a single
setting.
- Make available to the user an "outline"
view of rendered 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).
- 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,
and the title
attribute is a label for its element.
- 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, 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 in content, 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.
- User agents are expected to compute information about recently traversed
links. For the other link information of this checkpoint, the user agent is
only required to make available what is present in content.
- The user agent is not required to compute or make available information
that requires retrieval of linked Web resources.
- Highlight the viewport with the current focus (including any frame that
takes current focus).
- For graphical viewports, as part of
satisfying provision one of this checkpoint, provide at least one highlight
mechanism that 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 of this checkpoint involve rendered text size, font family,
rendered text foreground and background
colors, or text decorations,
allow global
configuration and offer 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, or the
proportion of a Web page that has been viewed).
- 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 or as a relative size in bytes. See
checkpoint 1.3 for more
information about text versions of messages to the user, including messages
about position information.
- For two-dimensional spatial
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.
Allow users to configure the user agent so that
frequently performed tasks are made convenient, and allow users to save their
preferences.
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, and keyboard
configuration. 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.
Provide information to the user about
current user preferences for input configurations.
- To satisfy this checkpoint, the user agent may make available binding
information in a centralized fashion (e.g., a list of bindings) or a
distributed fashion (e.g., by listing keyboard shortcuts in user interface
menus). See related documentation checkpoints
12.2,
12.3, and
12.5.
Provide a centralized view of the
current author-specified input configuration.
- The user agent may satisfy this checkpoint by providing different views for
different input modalities (keyboard, pointing device, and
voice).
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 an entire
document to learn about available bindings.
Allow the user to override any binding that is part of the
user agent default input configuration.
- The user agent is not required to allow the user to override conventional
bindings for the operating environment (e.g.,
for access to help).
- The override requirement only applies to bindings for the
same input modality (e.g., the user must be able to override a keyboard binding
with another keyboard binding).
- This checkpoint excludes the requirements of checkpoint 11.4.
- Conformance detail: For user agent
features
Note: See checkpoint 11.5 for default input configuration requirements
and checkpoint 12.3
for information about their documentation.
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.
- The user agent may satisfy the requirements of provision two of this
checkpoint with a "single-key mode." In a single-key mode, the complete set of
functionalities required by provision two must be available through single-key
bindings. The user must be able to remain in single-key mode until explicitly
requesting to leave it.
- 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 of this checkpoint 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, then provision two of this checkpoint 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 checkpoint 11.5.
- This checkpoint is mutually exclusive of checkpoint 11.3 since it is specific to the keyboard and to
emphasize the importance of easy keyboard access.
- Conformance detail: 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 content focus to the
next enabled element in
document order, and move content focus to the previous enabled
element in document order (checkpoints 9.3 and 9.7);
activate the link designated by the content focus (checkpoints
1.1 and
9.1);
search for text, search again for same text (checkpoint
9.8);
increase the scale of rendered text, and decrease the scale
of rendered text (checkpoint 4.1);
increase global volume, and decrease global volume (checkpoint
4.7);
and
stop, pause, resume, and navigate efficiently selected audio and
animations, including video and animated
images (checkpoint 4.5).
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 a URI for a new resource;
add a URI to favorites (i.e., bookmarked resources);
view favorites;
reload a resource;
interrupt a request to load or reload a resource;
for graphical viewports: navigate forward and backward through rendered
content by approximately the height of the viewport; and
for user agents that render content in lines of (at least) text: move the
point of regard to the next and previous line.
- 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
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 user agent default
profiles, profiles created by the same user,
and no profile (i.e., the user agent default settings).
- This checkpoint does not require the user agent to provide multiple default
profiles.
- 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 user
agent). Portable user profiles are very useful, however.
- Conformance detail: For user agent
features
- For graphical user agent user interfaces
with tool bars, allow the user to configure the position of
user agent user interface
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.
Ensure that the user can learn about software
features that benefit accessibility from the documentation. Ensure that the
documentation is accessible.
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.
- Ensure that at least one version of the user
agent documentation conforms
to at least level Double-A of the Web Content Accessibility Guidelines 2.0
[WCAG20].
- Provide documentation of all user agent
features that benefit accessibility.
- 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.
A centralized view is sufficient to satisfy this checkpoint and is required to
satisfy checkpoint
12.5.
- 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).
- Conformance detail: 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.
Provide documentation of the default user agent
input
configuration (e.g., the default keyboard bindings).
- 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.
- Provide documentation of changes since the
previous version of the user agent to features that benefit
accessibility.
- Provide a centralized view of all
features of the user agent that benefit accessibility, in a dedicated section
of the documentation.
- A centralized view is required to satisfy this checkpoint and is sufficient
to satisfy checkpoint
12.2.
Glossary Changes
Base Background: The base background is the background of the content as a whole, such that no content may be layered behind it. In graphics applications, the base background is often referred to as the canvas.).
blinking text: text whose visual rendering alternates between visible and invisible at any rate of change.
This glossary is normative. However, 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 the 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 explicit 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, or video card.
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, the conventional input APIs of the
target user agent are for the mouse and
keyboard. For touch screen devices or mobile devices, conventional input
APIs may include stylus, buttons, and voice. 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 and parsing markup) 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, and content transformations (e.g., to make tables more
accessible).
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. These technologies include
wheelchairs, reading machines, devices for grasping, text telephones, and
vibrating pagers. 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 prerecorded 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. 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 should be made available to users only under certain conditions (e.g., based on user preferences or operating environment limitations). Some examples include:
- The
alt
attribute of the IMG
element in HTML 4 [HTML4].
OBJECT
elements in HTML 4 [HTML4].
- The
switch
element and test attributes in SMIL 1.0 [SMIL].
- The
NOSCRIPT
and NOFRAMES
elements in HTML 4
[HTML4].
Note: Specifications vary in how completely they define how and when to render conditional content.
Conditional content stack: The set of conditional content items for a given position in content.
The items may be mutually exclusive (e.g., regular contrast graphic vs.
high contrast graphic) or non-exclusive (e.g., caption track that can
play at the same time as a sound track).
- 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, or via style sheets or scripts). The results of "configuration" might not
take effect immediately (e.g., due to time spent reinitializing the system,
initiating a new session, or rebooting the system).
In order to be able to configure and control the user agent, the user needs
to be able to "write" as well as "read" 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 can 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.
User agents may allow users to choose configurations based on various
parameters, such as hardware capabilities or natural language preferences.
Note: In this document, the noun "control" refers to a
user interface
control.
- 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 (which may be conditional content) is either a
null value or an empty string (i.e., one that is zero characters long). 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
- In this document, device-independence refers to the
desirable property that operation of a user agent feature is not bound to only
one 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 (e.g., from style sheets, scripts, or transformations),
produced as a result of preferences set within the user agent, or added as the
result of a repair performed automatically by the user agent. Some data that is
part of the document object is routinely rendered (e.g., in HTML, what
appears between the start and end tags of elements and the values of attributes
such as
alt
, title
, and summary
). Other
parts of the document object are generally processed 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
and id
. Most of the requirements of this
document apply to the document object after its construction. However, a few
checkpoints (e.g., checkpoints 2.7 and
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.
- Document character set
- In this document, a document character set (a concept from
SGML) is a collection of abstract characters that a format specification allows
to appear in an instance of the format. A document character set consists of:
- A "repertoire": A set of abstract characters, such as the Latin letter "A,"
the Cyrillic letter "I," and the Chinese character meaning "water."
- 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 does not 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 the text portion of
the document source.
- Documentation
- Documentation refers to information that supports the use
of a user agent. This information may be found, for example, in manuals,
installation instructions, the help system, and tutorials. Documentation may be
distributed (e.g., some parts may be delivered on CD-ROM, others on the Web).
See guideline 12
for information about documentation requirements.
- Element, element type
- This document uses the terms "element" and "element type"
primarily 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 can 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. One example of a disabled
element is a menu item that is unavailable in the current session; it might be
"grayed out" to show that it is disabled. 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, or
collated text transcripts for a movie) 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).
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 and other conditional content 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 events, changes to
content, loading of content, and requests from the operating environment. 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 through the user agent user
interface (not through rendered content),
the focus, or the selection. User requests are made, for
example, through user agent user interface
controls and keyboard bindings.
- 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 instead of "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" (required by
checkpoint
9.1) 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, i.e., it may be "set" on an enabled element, programmatically
or through the user interface. Some content specifications (e.g., HTML, CSS)
allow authors to associate behavior with focus set and unset
events.
- 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, designers of word processing software 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
that, rather than designating pieces of content, it designates zero or one
control of the
user agent user interface
that has associated behaviors (e.g., a radio button, text box, or menu).
On the screen, the user agent may highlight the content focus in a variety of
ways, including through colors, fonts, graphics, and magnification. The user
agent may also highlight the content focus 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 (including text, colors, graphics, images, and animations) 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
- This document uses the term "image" to refer (as is
commonly the case) to pictorial content. However, in this
document, term image is limited to 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, and voice commands). The default input
configuration is the set of bindings the user finds after installation of the
software; see checkpoint 12.3 for relevant documentation requirements.
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 or by programmatic enablement, may have associated behaviors to be executed or carried out as a result of user or programmatic interaction."
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. @@edit the rest@@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
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 [WCAG 2.0, ATAG 2.0]
- 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.
- plug-in [ATAG 2.0]
- 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 during an audio rendering or a
cursor position 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, and
selection. The stability of the point of
regard is addressed by guideline 5 and
checkpoint
9.4.
- 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, and natural language preferences. In
operating environments with
distinct user accounts, profiles enable users to reconfigure software quickly
when they log on. Users may share their profiles with one another.
Platform-independent profiles are useful for those who use the same user agent
on different platforms.
- prompt [ATAG 2.0]
- Any user agent initiated
request for a decision or piece of information from users.
- 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, or on a mobile device. Style
information (e.g., fonts, colors, and synthesized speech prosody) 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 at installation is called the property's
default value.
- recognize
- Authors encode information in many ways, including in
markup languages, style sheet languages, scripting languages, and protocols.
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 a heading using a visual effect alone (e.g.,
just 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 is not rendered but that may influence
the graphical rendering (e.g., layout) of other content. Similarly,
silent
content is content that is not rendered but that may influence
the audio rendering of other content. 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" refers to the text portion of repair content.
Some error conditions that may lead to the generation of repair content
include:
- Erroneous or incomplete content (e.g., ill-formed markup, invalid markup,
or missing conditional
content that is required by format specification);
- Missing resources for handling or rendering content (e.g., the user agent
lacks a font family to display some characters, or the user agent does not
implement a particular scripting language).
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 (programming) 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 (possibly empty) range of
content. Generally, user agents limit the
type of content that may be selected to text content (e.g., one or more
fragments of text). In some user agents, the value of the
selection is constrained by the structure
of the document tree.
On the screen, the selection may be highlighted in a variety of ways, including
through colors, fonts, graphics, and magnification. 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, including for cut and
paste operations, to designate a specific element in a document for the
purposes of a query, and as an indication of point of regard.
The selection has state, i.e., it may be "set," programmatically or through
the user interface.
In this document, each viewport is expected to have at most one selection.
When several viewports coexist, at most one viewport's
selection responds to input events; this is called the current selection.
See the section on the
Selection label for
information about implementing a selection and
conformance.
Note: Some user agents may also implement a selection for
designating a range of information in the user agent user interface.
The current document only includes requirements for a content
selection mechanism.
- serial access,
sequential navigation
- In this document, the expression "serial access" refers to
one-dimensional access to rendered content.
Some examples of serial access include listening to an audio stream or watching
a video (both of which involve one temporal dimension), or reading a series of
lines of braille one line at a time (one spatial dimension). Many users with
blindness have serial access to content rendered as audio, synthesized speech,
or lines of braille.
The expression "sequential navigation" refers to navigation through an
ordered set of items (e.g., the enabled elements in a document, a
sequence of lines or pages, or a sequence of menu options). Sequential
navigation implies that the user cannot skip directly from one member of the
set to another, in contrast to direct or structured navigation (see
guideline 9 for
information about these types of navigation). Users with blindness or some
users with a physical disability may navigate content sequentially (e.g., by
navigating through links, one by one, in a graphical viewport with or without
the aid of an assistive technology). Sequential navigation is important to
users who cannot scan rendered content visually for context and also benefits
users unfamiliar with content. The increments of sequential navigation may be
determined by a number of factors, including element type (e.g., links only),
content structure (e.g., navigation from heading to heading), and the current
navigation context (e.g., having navigated to a table, allow navigation among
the table cells).
Users with serial access to content or who navigate sequentially may require
more time to access content than users who use direct or structured
navigation.
- 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
or a particular scripting language), 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.
- synchronize
- In this document, "to synchronize" refers to the act of
time-coordinating two or more presentation components (e.g., a
visual track with captions, or several
tracks in a multimedia presentation). 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.
- technology (Web content) - or shortened to technology [WCAG 2.0, ATAG 2.0]
- A mechanism for encoding instructions to be rendered, played or executed by user agents. Web Content technologies may include markup languages, data formats, or programming languages that authors may use alone or in combination to create end-user experiences that range from static Web pages to multimedia presentations to dynamic Web applications. Some common examples of Web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.
- 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.
- 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 created by hand 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:
- The software and documentation components that together,
conform to the requirements of this
document. This is the most common use of the term in this document and is the
usage in the checkpoints.
- 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.
- 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 content in that markup language;
others do not. 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,
user interface
control
- For the purposes of this document, user interface includes
both:
- the user agent user
interface, i.e., the controls (e.g., menus, buttons, prompts, and
other components for input and output) 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 controls, links, and applets.
The document distinguishes them only where required for clarity. For more
information, see the section on
requirements for content, for user
agent features, or both.
The term "user interface control" refers to a component of the user agent
user interface or the content user interface, distinguished where
necessary.
- user styles
- User styles are style property
values that come from user interface settings, user style sheets, or other
user interactions.
- view, viewport
- The user agent renders content through one or more
viewports. Viewports include windows, frames, pieces of paper, loudspeakers,
and virtual magnifying glasses. A viewport may contain another viewport (e.g.,
nested frames). User agent user interface
controls such as prompts, menus, and alerts are not viewports.
Graphical and tactile viewports have two spatial
dimensions. A viewport may also have
temporal dimensions, for instance when audio, speech, animations, and movies
are rendered. When the dimensions (spatial or temporal) of rendered content
exceed the dimensions of the viewport, 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. Examples include: when the user can
only view a portion of a large document through a small graphical viewport, or
when audio content has already been played.
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.
- 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.
- 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].