Techniques for User Agent Accessibility Guidelines 1.0
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This section lists each checkpoint of "User Agent Accessibility Guidelines
1.0" [UAAG10] along with some possible
techniques for satisfying it. Each checkpoint definition includes a link to the
checkpoint definition in "User Agent Accessibility Guidelines 1.0". Each
checkpoint definition is followed by one or more of the following:
- Notes and rationale: Additional rationale and explanation
of the checkpoint;
- Example techniques: Some techniques to illustrate how a
user agent might satisfy the requirements of the checkpoint;
- Doing more: Techniques to achieve more than what is
required by the checkpoint;
- Related techniques: Links to other techniques in section
3. The accessibility topics of section 3 generally apply to more than one
checkpoint.
- References: References to other guidelines,
specifications, or resources.
Note: Most of the techniques in this document are designed
for mainstream (graphical) browsers and multimedia players. However, some of
them also make sense for assistive technologies and other user agents. In
particular, techniques about communication between user agents will benefit
assistive technologies. Refer, for example, to the appendix on loading assistive technologies
for access to the document object model.
Each checkpoint in this document is assigned a priority that indicates its
importance for users with disabilities.
- [Priority
1]
- This checkpoint must be satisfied by user agents,
otherwise one or more groups of users with disabilities will find it impossible
to access the Web. Satisfying this checkpoint is a basic requirement for
enabling some people to access the Web.
- [Priority
2]
- This checkpoint should be satisfied by user agents,
otherwise one or more groups of users with disabilities will find it difficult
to access the Web. Satisfying this checkpoint will remove significant barriers
to Web access for some people.
- [Priority
3]
- This checkpoint may be satisfied by user agents to make it
easier for one or more groups of users with disabilities to access information.
Satisfying this checkpoint will improve access to the Web for some people.
Note: This information about checkpoint priorities is
included for convenience only. For detailed information about conformance to
"User Agent Accessibility Guidelines 1.0"
[UAAG10], please refer to that document.
Checkpoints
-
1.1 Ensure that the user can operate the user agent fully through
keyboard input alone. [Priority 1] Both
content and user agent. (
Checkpoint 1.1)
- 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, operate controls of the
user interface, etc., all entirely through keyboard input. It is also possible
to claim conformance
to User Agent Accessibility Guidelines 1.0
[UAAG10] for full support through pointing device input and voice
input. See the section on input modality
labels in UAAG 1.0.
-
- For instance, the user must be able to do the following through the
keyboard alone (or pointing device alone or voice alone):
- Select
content and operate on it. For example, if the user can select rendered text
with the mouse and make it the content of a new link by pushing a button, they
also need to be able to do so through the keyboard and other supported devices.
Other operations include cut, copy, and paste.
- Set the focus on
viewports and on enabled elements.
- Install, configure, uninstall, and update the user agent software.
- Use the graphical user
interface menus. Some users may wish to user the graphical user
interface even if they cannot use or do not wish to use the pointing
device.
- Fill out forms.
- Access documentation.
- Suppose a user agent does not allow complete operation through the
keyboard alone. It is still possible to claim conformance for the
user agent in conjunction with a special module designed to "fill in the
gap".
-
-
1.2 For the element with
content focus, allow the user to activate
any explicitly associated input device event
handlers through keyboard input alone.
[Priority 1] Content only. (
Checkpoint 1.2)
- Note: The requirements for this
checkpoint refer to any explicitly associated input device event
handlers associated with an element, independent of the input
modalities for which the user agent conforms. For example, suppose that an
element has an explicitly associated handler for pointing device events. Even
when the user agent only conforms for keyboard input (and does not conform for
the pointing device, for example), this checkpoint requires the user agent to
allow the user to activate that handler with the keyboard. This checkpoint is
an important special case of checkpoint 1.1. Please refer to the checkpoints of guideline 9 for more information about
focus requirements.
-
- For example, users without a pointing device (such as some users who are
blind or have physical disabilities) need to be able to activate
form controls
and links (including the links in a client-side image map).
-
- For example, in HTML 4 [HTML4], input device event handlers
are described in
section 18.2.3. They are:
onclick
, ondblclick
,
onmousedown
, onmouseover
, onmouseout
,
onfocus
, onblur
, onkeypress
,
onkeydown
, and onkeyup
.
- In "Document Object Model (DOM) Level 2 Events Specification"
[DOM2EVENTS], focus and activation types are discussed in
section 1.6.1. They are:
DOMFocusIn
, DOMFocusOut
,
and DOMActivate
. These events are specified independent of a
particular input device type.
- In "Document Object Model (DOM) Level 2 Events Specification"
[DOM2EVENTS], mouse event types are discussed in
section 1.6.2. They are:
click
, mousedown
,
mouseup
, mouseover
, mousemove
and
mouseout
.
- The DOM Level 2 Event specification does not provide a key event
module.
- Sequential technique: Add each input device event handler to the serial
navigation order (refer to checkpoint
9.2). Alert the user when the user has navigated to an event handler, and
allow activation. For example, an link that also has a onMouseOver and
onMouseOut event handlers defined, might generate three "stops" in the
navigation order: one for the link and two for the event handlers. If this
technique is used, allow configuration so that input device event handlers are
not inserted in the navigation order.
- Query technique: Allow the user to query the element with content focus for
a menu of input device event handlers.
- Descriptive information about handlers can allow assistive technologies to
choose the most important functions for activation. This is possible in the
Java Accessibility API [JAVAAPI], which provides an an
AccessibleAction Java interface. This interface provides a list of actions and
descriptions that enable selective activation. See also checkpoint
6.3.
- Using MSAA [MSAA] on the Windows platform:
- Retrieve the node in the document object that has current focus.
- Call the
IHTMLDocument4::fireEvent
method on that node.
-
- See image map
techniques.
-
- For example,
section 16.5 of the SVG 1.0 Candidate Recommendation [SVG]
specifies processing order for user interface events.
-
- 1.3 Ensure that every message (e.g.,
prompt,
alert, notification, etc.) that is a non-text
element and is part of the user agent user interface has a text
equivalent. [Priority 1] User
agent only. (Checkpoint
1.3)
- Note: For example, if the user is
alerted of an event by an audio cue, a visually-rendered text equivalent in the
status bar would satisfy this checkpoint. Per checkpoint 6.4, a text equivalent for each such message must
be available through a standard API. See also checkpoint 6.5 for requirements for programmatic alert of
changes to the user interface.
-
- User agents should use modality-specific messages in the user interface
(e.g., graphical scroll bars, beeps, and flashes) as long as redundant
mechanisms are available or possible. These redundant mechanisms will benefit
all users, not just users with disabilities. For instance, mechanisms that are
redundant to audio will benefit individuals who are deaf, hard of hearing, or
operating the user agent in a noisy or silent environment where the use of
sound is not practical.
-
- Render text messages on the status bar of the graphical user interface.
Allow users to query the viewport for this status information (in addition to
having access through graphical rendering).
- Make available information in a manner that allows other software to
present it according to the user's preferences. For instance, if the graphical
user agent uses proportional scroll bars to indicate the position of the
viewport in content, make available this same information in text form. For
instance, this will allow other software to render the proportion of content
viewed as speech or as braille.
-
- Allow configuration to render or not render status information (e.g., allow
the user to hide the status bar).
-
Checkpoints
- 2.1 For all format specifications
that the user agent
implements, make content
available through the rendering processes described by those specifications.
[Priority 1] Content only. (Checkpoint
2.1)
- Note: This includes format-defined
interactions between author preferences and user preferences/capabilities
(e.g., when to render the "
alt
" attribute
in HTML [HTML4], the rendering order of
nested OBJECT
elements in HTML, test attributes in SMIL
[SMIL], and the cascade in CSS2
[CSS2]). If a conforming user agent does not render a content type,
it should allow the user to choose a way to handle that content (e.g., by
launching another application, by saving it to disk, etc.). This checkpoint
does not require that all content be available through each
viewport.
-
- Provide access to attribute values (one at a time, not as a group). For
instance, allow the user to select an element and read values for all
attributes set for that element. For many attributes, this type of inspection
should be significantly more usable than a view of the text source.
- When content changes dynamically (e.g., due to embedded scripts or content
refresh), users need to have access to the content before and after the
change.
- Make available information about abbreviation and acronym expansions. For
instance, in HTML, look for abbreviations specified by the ABBR and ACRONYM
elements. The expansion may be given with the "title" attribute (refer to the
Web Content Accessibility Guidelines 1.0
[WCAG10], checkpoint 4.2). To provide expansion information, user
agents may:
- Allow the user to configure that the expansions be used in place of the
abbreviations,
- Provide a list of all abbreviations in the document, with their expansions
(a generated glossary of sorts)
- Generate a link from an abbreviation to its expansion.
- Allow the user to query the expansion of a selected or input
abbreviation.
- If an acronym has no explicit expansion in one location, look for another
occurrence in content with an explicit expansion. User agents may also look for
possible expansions (e.g., in parentheses) in surrounding context, though that
is a less reliable technique.
-
- See the sections on access to
content, link techniques, table techniques, frame techniques, and form techniques.
-
- Sections 10.4 ("Client Error 4xx") and 10.5 ("Server Error 5xx") of the
HTTP/1.1 specification [RFC2616] state that user agents
should have the following behavior in case of these error conditions:
Except when responding to a HEAD request, the server SHOULD include an
entity containing an explanation of the error situation, and whether it is a
temporary or permanent condition. These status codes are applicable to any
request method. User agents SHOULD display any included entity to the user.
-
- 2.2 For all text formats that the user
agent
implements, provide a view of the
text source. Text formats include at least the following: (1) all
media objects given an Internet media type of "text" (e.g., text/plain,
text/HTML, or text/*), and (2) all SGML and XML applications, regardless of
Internet media type (e.g., HTML 4.01, XHTML 1.1, SMIL, SVG, etc.). [Priority 1] Content only. (Checkpoint
2.2)
- Note: Refer to
[RFC2046], section 4.1 for information about the "text" Internet
media type. A user agent would also satisfy this checkpoint by providing a
source view for any text format, not just implemented text formats.
-
- In general, user agent developers should not rely on a "source view" to
convey information to users, most of whom are not familiar with markup
languages. A source view is still important as a "last resort" to some users as
content might not otherwise be accessible at all.
-
- Make the text view useful. For instance, enable links (i.e.,
URIs), allowing searching and other navigation within the view.
- A source view is an easily-implementable view that will help users inspect
some types of content, such as style sheet fragments or scripts. This does not
mean, however, that a source view of style sheets is the best user
interface for reading or changing style sheets.
-
- Provide a source view for any text format, not just implemented text
formats.
-
- 2.3
Allow global
configuration so that, for each piece of unrendered
conditional content "C", the user agent alerts the user to the existence of the content
and provides access to it. Provide access to this content according to format
specifications or where unspecified, as follows. If C has a close relationship
(e.g., C is a summary, title, alternative, description, expansion, etc.) with
another piece of rendered content D, do at least one of the following: (1a)
render C in place of D, (2a) render C in addition to D, (3a) provide access to
C by querying D, or (4a) allow the user to follow a link to C from the context
of D. If C does not have a close relationship to other content (i.e., a
relationship other than just a document tree relationship), do at least one of
the following: (1b) render a
placeholder for C, (2b) provide access to C by query (e.g., allow
the user to query an element for its
attributes), or (3b) allow the user to follow a link in context to
C. [Priority 1] Content only. (
Checkpoint 2.3)
- Note: The configuration requirement of
this checkpoint is global; the user agent is only required to provide one
switch that turns on or off these alert and access mechanisms. To satisfy this
checkpoint, the user agent may provide access on an element-by-element basis
(e.g., by allowing the user to query individual elements) or for all elements
(e.g., by offering a configuration to render conditional content all the time).
For 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).
-
- Allow users to choose more than one piece of
conditional content at a given time. For instance,users with low
vision may want to view images (even imperfectly) but require a text
equivalent for the image; the
text may be rendered with a large font or as speech.
-
- In HTML 4 [HTML4], conditional content
mechanisms include the following:
- Allow the user to
configure how the user agent renders a long description (e.g., "longdesc"
in HTML 4 [HTML4]). Some possibilities
include:
- Render the long description in a separate view.
- Render the long description in place of the associated element.
- Do not render the long description, but allow the user to query whether an
element has an associated long description (e.g., with a context-sensitive
menu) and provide access to it.
- Use an icon (with a text
equivalent) to indicate the presence of a long description.
- Use an audio cue to indicate the presence of a long description when the
user navigates to the element.
- For an object (e.g., an image) with an author-specified geometry that the
user agent does not render, allow the user to configure how the conditional
content should be rendered. For example, within the specified geometry, by
ignoring the specified geometry altogether, etc.
- For multimedia presentations with several alternative tracks, ensure access
to all tracks and allow the user to select individual tracks. The QuickTime
player [QUICKTIME] allows users to turn
on and off any number of tracks separately. For example, construct a list of
all available tracks from short descriptions provided by the author (e.g.,
through the "title" attribute).
- For multimedia presentations with several alternative tracks, allow users
to choose tracks based on natural language preferences. SMIL 1.0
[SMIL] allows users to specify
captions in different natural languages. By setting language
preferences in the SMIL player (e.g., the G2 player [G2]),
users may access captions (or audio) in different languages. Allow users to
specify different languages for different content types (e.g., English audio
and Spanish captions).
- If a multimedia presentation has several captions
(or subtitles) available, allow the user to choose from among them. Captions
might differ in level of detail, reading levels, natural
language, etc. Multilingual audiences may wish to have captions in
different natural
languages on the screen at the same time. Users may wish to use both
captions and auditory descriptions concurrently as well.
- Make apparent through the user
agent user interface which
audio tracks are meant to be played separately.
-
- Make information available with different levels of detail. For example,
for a voice
browser, offer two options for HTML
IMG
elements:
- Speak only "alt" text by default, but allow the user to hear "longdesc"
text on an image by image basis.
- Speak "alt" text and "longdesc" for all images.
- Allow the user to configure different natural
language preferences for different types of
conditional content (e.g., captions and auditory descriptions).
Users with disabilities may need to choose the language they are most familiar
with in order to understand a presentation for which supplementary tracks are
not all available in all desired languages. In addition, some users may prefer
to hear the program audio in its original language while reading captions in
another, fulfilling the function of subtitles or to improve foreign language
comprehension. In classrooms, teachers may wish to configure the language of
various multimedia elements to achieve specific educational goals.
-
- See the section on access to
content.
-
- 2.4 For
content where user input is only possible
within a finite time interval controlled by the user agent, allow
configuration to make the time interval "infinite". Do this by
pausing automatically at the end of each time interval where user input is
possible, and resuming automatically after the user has explicitly completed
input. In this configuration, alert the user when the session has been paused
and which enabled
elements are time-sensitive.
[Priority 1] Content only. (Checkpoint
2.4)
- Note: In this configuration, the user
agent may have to pause the presentation more than once if there is more than
one opportunity for time-sensitive input. In SMIL 1.0
[SMIL], for example, the "
begin
", "end
",
and "dur
"
attributes synchronize presentation components. The user may
explicitly complete input in many different ways (e.g., by following a link
that replaces the current time-sensitive resource with a different resource).
This checkpoint does not
apply when the user agent cannot recognize the time
interval in the presentation format, or when the user agent cannot control the
timing (e.g., because it is controlled by the server).
-
- The requirement to pause at the end (rather than at the beginning)
of a time-interval is to allow the user to review content that may change
during the elapse of this time.
- This checkpoint requires the user agent to pause a presentation
automatically, whereas the pause requirement of checkpoint 4.5 is
manual.
-
- Some HTML user agents recognize time intervals specified through the
META
element, although this usage is not defined in HTML 4
[HTML4].
- Render time-dependent links as a static list that occupies the same screen
real estate; authors may create such documents in SMIL 1.0
[SMIL]. Include temporal context in the list of links. For example,
provide the time at which the link appeared along with a way to easily jump to
that portion of the presentation.
-
- The checkpoint requires that the user agent make the time interval
infinite, but one consequence of this is that the user needs to confirm
manually the end of input. The user agent may provide additional configurations
to lengthen time intervals so that manual confirmation at the end of input is
not required. For instance, the user agent might include a configuration to
allow the user three to five times the author's specified time interval for
input. Or, the user agent might include a configuration to add additional time
to each time interval (e.g., 10 extra seconds).
- Allow users to view a list of all media elements or links of the
presentations sorted by start or end time or alphabetically.
-
- Refer to section
4.2.4 of SMIL 1.0 [SMIL] for information about the SMIL
time model.
-
-
2.5 Allow
configuration or control so
that text
transcripts, collated text transcripts, captions,
and auditory
descriptions are rendered at the same time as the associated audio
tracks and visual
tracks. [Priority 1] Content
only. (
Checkpoint 2.5)
- Note: This checkpoint is an important
special case of checkpoint
2.1.
-
- Allow users to turn on and off auditory descriptions and captions.
- For the purpose of applying this clause, SMIL 1.0
[SMIL] user agents should recognize as captions any media object
whose reference from SMIL is guarded by the '
system-captions
' test
attribute.
- SMIL user agents should allow users to configure whether they want to view
captions, and this user interface switch should be bound to the
'
system-captions
' test attribute. Users should be able to indicate
a preference for receiving available auditory descriptions, but SMIL 1.0
[SMIL] does not include a mechanism analogous to 'system-captions'
for auditory descriptions, though [SMIL20] is expected to.
- Another SMIL 1.0 test attribute, '
system-overdub-or-captions
',
allows users to choose between subtitles and overdubs in multilingual
presentations. User agents should not interpret a value of
'caption
' for this test attribute as meaning that the user prefers
accessibility captions; that is the purpose of the
'system-captions
' test attribute. When subtitles and accessibility
captions are both available, users who are deaf may prefer to view captions, as
they generally contain information not in subtitles: information on music,
sound effects, who is speaking, etc.
- User agents that play QuickTime movies should allow the user to turn on and
off the different tracks embedded in the movie. Authors may use these
alternative tracks to provide content for accessibility purposes. The Apple
QuickTime player provides this feature through the menu item "Enable
Tracks."
- User agents that play Microsoft Windows Media Object presentations should
provide support for Synchronized Accessible Media Interchange (SAMI
[SAMI]), a protocol for creating and displaying captions) and should
allow users to configure how captions are viewed. In addition, user agents that
play Microsoft Windows Media Object presentations should allow users to turn on
and off other
conditional content, including auditory description and alternative
visual
tracks.
-
- User agents that implement SMIL 1.0
[SMIL] should implement the "Accessibility Features of SMIL"
[SMIL-ACCESS].
-
- 2.6 Respect synchronization cues
during rendering. [Priority 1] Content
only. (Checkpoint
2.6)
- Note: This checkpoint is an important
special case of checkpoint
2.1.
-
- The term "synchronization cues" refers to pieces of information that may
affect synchronization, such as the size and expected duration of tracks and
their segments, the type of element and how much those elements can be sped up
or slowed down (both from technological and intelligibility standpoints).
- Captions
and auditory
descriptions may not make sense unless rendered synchronously with
related video or audio content. For instance, if someone with a hearing
disability is watching a video presentation and reading associated captions,
the captions should be
synchronized with the audio so that the individual can use any
residual hearing. For auditory descriptions, it is crucial that an audio
track and an auditory description track be synchronized to avoid
having them both play at once, which would reduce the clarity of the
presentation.
-
- The idea of "sensible time-coordination" of components in the definition of
synchronize centers on the idea of simultaneity of presentation, but
also encompasses strategies for handling deviations from simultaneity resulting
from a variety of causes. Consider how deviations might be handled for captions
for a multimedia presentation such as a movie clip. Captions consist of a text
equivalent of the audio track that is synchronized with the visual
track. Typically, a segment of the captions appears visually near
the video for several seconds while the person reads the text. As the visual
track continues, a new segment of the captions is presented. However, a problem
arises if the captions are longer than can fit in the display space. This can
be particularly difficult if due to a visual disability, the font size has been
enlarged, thus reducing the amount of rendered caption text that can be
presented. The user agent needs to respond sensibly to such problems, for
example by ensuring that the user has the opportunity to navigate (e.g., scroll
down or page down) through the caption segment before proceeding with the
visual presentation and presenting the next segment.
- Developers of user agents need to determine how they will handle other
synchronization challenges, such as:
- Under what circumstances will the presentation automatically pause? Some
circumstances where this might occur include:
- the segment of rendered caption text is more than can fit on the visual
display
- the user wishes more time to read captions or the collated text
transcript
- the auditory description is of longer duration than the natural pause in
the audio.
- Once the presentation has paused, then under what circumstances will it
resume (e.g., only when the user signals it to resume, or based on a predefined
pause length)?
- If the user agent allows the user to jump to a location in a presentation
by activating a link, then how will related tracks behave? Will they jump as
well? Will the user be able to return to a previous location or undo the
action?
- Developers of user agents need to anticipate many of the challenges that
may arise in synchronization of diverse tracks.
-
- 2.7 Allow
configuration to generate
repair text when the user agent
recognizes that the author has failed to provide
conditional content that was required by the format specification.
The user agent may satisfy this checkpoint by basing the repair text on any of
the following available sources of information: URI reference, content type, or
element type. [Priority 2] Content only.
(Checkpoint
2.7)
- Note: Some markup languages (such as HTML 4
[HTML4] and SMIL 1.0 [SMIL] require the author to provide
conditional content for some elements (e.g., the "
alt
" attribute
on the IMG
element). Repair text based on URI reference, content
type, or element type is sufficient to satisfy the checkpoint, but may not
result in the most effective repair. Information that may be
recognized as relevant to repair might not be "near" the missing
conditional content in the document object. For instance, instead of
generating repair text on a simple URI reference, the user agent might look for
helpful information near a different instance of the URI reference in the same
document object, or might retrieve useful information (e.g., a title) from the
resource designed by the URI reference.
-
- Some examples of missing conditional content that is required by
specification:
- in HTML 4 [HTML4], "
alt
" is
required for the IMG
and AREA
elements (for
validation). In SMIL 1.0 [SMIL], on the other hand,
"alt
" is not required on media objects.
- whatever the format, text equivalents for non-text content are required by
the Web Content Accessibility Guidelines 1.0
[WCAG10].
- Conditional content may come from markup, inside images (e.g., refer to
"Describing and retrieving photos using RDF and HTTP"
[PHOTO-RDF]), etc.
-
- When HTTP is used, HTTP headers provide information about the URI of the Web
resource ("Content-Location") and its type ("Content-Type"). Refer
to the HTTP/1.1 specification [RFC2616], sections 14.14 and
14.17, respectively. Refer to "Uniform Resource Identifiers (URI): Generic
Syntax" ([RFC2396], section 4) for
information about URI references, as well as the HTTP/1.1 specification
[RFC2616], section 3.2.1.
-
- When configured to generate text, also inform the user (e.g., in the
generated text itself) that this content was not provided by the author as a
text equivalent.
-
- See content repair techniques,
and cell header repair strategies.
-
- The "Altifier Tool" [ALTIFIER] illustrates smart
techniques for generating text
equivalents (for images, etc.) when the author has not specified
any.
-
- 2.8 Allow
configuration so that when the user agent
recognizes that conditional content required by the format
specification is present but empty (e.g., the empty string), the user agent
either (1) generates no repair
text, or (2) generates repair text as described in checkpoint 2.7. [Priority 3] Content only. (Checkpoint
2.8)
- Note: In some authoring scenarios, an empty string of text
(e.g., "
alt=''
") may be considered to be an appropriate text
equivalent (for instance, when some non-text
content has no other function than pure decoration, or an image is
part of a "mosaic" of several images and doesn't make sense out of the mosaic).
Please refer to the Web Content Accessibility Guidelines 1.0
[WCAG10] for more information about text equivalents.
-
- User agents should render nothing in this case because the author may
specify an empty text equivalent for content that has no function in the page
other than as decoration.
-
- The user agent should not render generic labels such as "[INLINE]" or
"[GRAPHIC]" in the face of empty conditional content (unless configured to do
so).
- If no captioning information is available and captioning is turned on,
render "no captioning information available" in the captioning region of the
viewport (unless configured not to generate repair content).
-
- Labels (e.g., "[INLINE]" or "[GRAPHIC]") may be useful in some situations,
so the user agent may allow configuration to render "No author text" (or
similar) instead of empty conditional content.
-
- 2.9 Allow
configuration to render all
conditional content automatically. Provide access to this content
according to format specifications or where unspecified, by applying one of the
following techniques described in checkpoint 2.3: 1a, 2a, or 1b.
[Priority 3] Content only. (
Checkpoint 2.9)
- Note: The user agent satisfies this checkpoint if it
satisfies checkpoint 2.3
by applying techniques 1a, 2a, or 1b. 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).
-
- None.
-
-
2.10 Allow
configuration not to render content in unsupported natural
languages. Indicate to the user in context that author-supplied
content has not been rendered. [Priority 3]
Content only. (
Checkpoint 2.10)
- Note: For example, use a text
substitute or accessible graphical icon to indicate that content in a
particular language has not been rendered. This checkpoint does not require the
user agent to allow different configurations for different natural
languages.
-
- Rendering content in an unsupported language (e.g., as "garbage"
characters) may confuse all users. However, this checkpoint is designed
primarily to benefit users who access content serially as it allows them to
skip portions of content that would be unusable as rendered.
- There may be cases when a conforming user agent supports a natural language
but a speech synthesizer does not, or vice versa.
-
- For instance, a user agent that doesn't support Korean (e.g., doesn't have
the appropriate fonts or voice set) should allow configuration to announce the
language change with the message "Unsupported language – unable to
render" (e.g., when the language itself is not recognized) or "Korean not
supported – unable to render" (e.g., when the language is recognized by
the user agent doesn't have resources to render it). The user should also be
able to choose no alert of language changes. Rendering could involve speaking
in the designated natural language in the case of a voice browser or screen
reader. If the natural language is not supported, the language change alert
could be spoken in the default language by a screen reader or voice
browser.
- A user agent may not be able to render all characters in a document
meaningfully, for instance, because the user agent lacks a suitable font, a
character has a value that may not be expressed in the user agent's internal
character encoding, etc. In this case,
section 5.4 of HTML 4
[HTML4] recommends the following for undisplayable characters:
- Adopt a clearly visible (or audible), but unobtrusive mechanism to alert
the user of missing resources.
- If missing characters are presented using their numeric representation, use
the hexadecimal (not decimal) form since this is the form used in character set
standards.
- When HTTP is used, HTTP headers provide information about content encoding
("Content-Encoding") and content language ("Content-Language"). Refer to the
HTTP/1.1 specification [RFC2616], sections 14.11 and
14.12, respectively.
- CSS2's attribute selector may be used with the HTML "lang" or XML
"xml:lang" attributes to control rendering based on
recognized natural language information. Refer also to the ':lang'
pseudo-class ([CSS2], section 5.11.4).
-
- See techniques for generated
content, which may be used to insert
text to indicate a language change.
- See content repair techniques
and accessibility and internationalization
techniques.
- See techniques for synthesized
speech.
-
- For information on language codes, refer to "Codes for the representation
of names of languages" [ISO639].
- Refer to "Character Model for the World Wide Web"
[CHARMOD]. It contains basic definitions and models, specifications
to be used by other specifications or directly by implementations, and
explanatory material. In particular, this document addresses early uniform
normalization, string identity matching, string indexing, and conventions for
URIs.
-
In addition to the techniques below, refer also to the section on user control of style.
Checkpoints
-
3.1 Allow
configuration not to render background images. In this
configuration, provide an option to alert the user when a background image is
available (but has not been rendered).
[Priority 1] Content only. (
Checkpoint 3.1)
- Note: This checkpoint only requires control of background
images for "two-layered renderings", i.e., one rendered background image with
all other content rendered "above it". When background images are not rendered,
user agents should render a solid background color instead (see checkpoint 4.3). In this
configuration, the user agent is not required to retrieve background images
from the Web.
-
- Background images may make it difficult or impossible to read superimposed
text or understand other superimposed content.
- This checkpoint does not address issues of multi-layered renderings and
does not require the user agent to change background rendering for multi-layer
renderings (refer, for example, to the 'z-index' property in Cascading Style
Sheets, level 2 ([CSS2], section 9.9.1).
-
- If background image are turned off, make available to the user associated
conditional content.
- In CSS, background images may be turned on/off with the
'background' and 'background-image' properties ([CSS2], section 14.2.1).
-
- Allow control of image depth in multi-layer presentations.
-
- 3.2
Allow
configuration not to render audio, video, or animated images except
on explicit request from the user. In this configuration, provide an option to
render a
placeholder in context for each unrendered source of audio, video,
or animated image. When placeholders are rendered, allow the user to view the
original author-supplied content associated with each placeholder. [Priority 1] Content only. (
Checkpoint 3.2)
- Note: This checkpoint requires configuration for content
rendered without any user interaction (including content rendered on load or as
the result of a script), as well as content rendered as the result of user
interaction that is not an explicit request (e.g., when the user activates a
link). When configured not to render content except on explicit user request,
the user agent is not required to retrieve the audio, video, or animated image
from the Web until requested by the user. See also checkpoint 3.8, checkpoint 4.5, checkpoint 4.9, and checkpoint
4.10.
-
- User agent may satisfy this checkpoint by treating content as invisible or silent (e.g., by implementing the
'visibility' property defined in section 11.2 of CSS 2
[CSS2]). However, this solution means that the content is processed,
though not rendered, and processing may cause undesirable side effects such as
firing events. Or, processing may interfere with the processing of other
content (e.g., silent audio may interfere with other sources of sound such as
the output of a speech synthesizer). This technique should be deployed with
caution.
- As a placeholder for an animated image, render a motionless image built
from the first frame of the animated image.
-
- 3.3
Allow
configuration to render animated or blinking text as motionless,
unblinking text. [Priority 1] Content only.
(
Checkpoint 3.3)
- Note: A "stock quote ticker" is an example of animated
text. This checkpoint does not apply for blinking and
animation
effects that are caused by mechanisms that the user agent cannot recognize. This
checkpoint requires configuration because blinking effects may be disorienting
to some users but useful to others, for example users who are deaf or hard of
hearing.
-
- The user agent may render the motionless text in a number of ways. Inline
is preferred, but for extremely long text, it may be better to render the text
in another viewport, easily reachable from the user's browsing context.
- Allow the user to turn off animated or blinking text through the user
agent user interface (e.g., by pressing the Escape key to
stop animations).
- Some sources of blinking and moving text are:
- The BLINK element in HTML. Note: The BLINK element is not
defined by a W3C specification.
- The MARQUEE element in HTML. Note: The MARQUEE element is
not defined by a W3C specification.
- The 'blink' value of the
'text-decoration' property in CSS ([CSS2], section 16.3.1).
- In JavaScript, to control the start and speed of scrolling for a
MARQUEE
element:
document.all.myBanner.start();
document.all.myBanner.scrollDelay = 100
-
- 3.4 Allow
configuration not to execute any executable
content (e.g., scripts and applets). In
this configuration, provide an option to alert the user when executable content
is available (but has not been executed).
[Priority 1] Content only. (Checkpoint
3.4)
- Note: Scripts and applets may provide
very useful functionality, not all of which causes accessibility problems.
Developers should not consider that the user's ability to turn off scripts is
an effective way to improve content accessibility; turning off scripts means
losing the benefits they offer. Instead, developers should provide users with
finer control over user agent or content behavior known to raise accessibility
barriers. The user should only have to turn off scripts as a last resort.
-
- Executable content includes scripts, applets, ActiveX controls, etc. This
checkpoint does not apply to plug-ins that are not part of
content.
- Executable content includes those that run "on load" (e.g., when a document
loads into a viewport) and when other events occur (e.g., user interface
events).
- The alert that scripts are available but not executed is important, for
instance, for helping users understand why some poorly authored pages without
script alternatives produce no content when scripts are turned off.
- Control of scripts is particularly important when they can cause the screen
to flicker, since people with photosensitive epilepsy can have seizures
triggered by flickering or flashing, particularly in the 4 to 59 flashes per
second (Hertz) range. Peak sensitivity to flickering or flashing occurs at 20
Hertz.
- Where possible, authors should encode knowledge in declarative formats
rather than in scripts. Knowledge and behaviors embedded in scripts is
difficult to extract, which means that user agents are less likely to be able
to offer control by the user over the script's effect.
-
- Do not make available the switch to turn scripts off only in the "Security"
part of the user interface as people may not think to look there. For instance,
include a "Scripts" entry in the index that allows people to find the switch
more easily.
-
- While this checkpoint only requires a global on/off switch, user agents
should allow finer control over executable content. For instance, in addition
to the global switch, allow users to turn off just input device event handlers,
or to turn on and off scripts in a given scripting language only.
-
- See the section on script
techniques.
-
-
3.5 Allow
configuration so that client-side content refreshes (i.e., those
initiated by the user agent, not the server) do not change
content except on explicit
user request. Allow the user to request the new content on demand
(e.g., by following a link or confirming a prompt). Alert the user, according
to the schedule specified by the author, whenever fresh content is available
(to be obtained on explicit user request).
[Priority 1] Content only. (
Checkpoint 3.5)
-
- Some HTML authors create a refresh effect by using a
META element with http-equiv="refresh" and the refresh rate specified in
seconds by the "content" attribute.
-
- Alert the user of pages that refresh automatically and allow them to
specify a refresh rate through the user agent user interface.
-
- Allow configuration for at least one very slow refresh rate (e.g., every 10
minutes).
- Retrieve new content without displaying it automatically. Allow the user to
view the differences (e.g., by highlighting or filtering) between the currently
rendered content and the new content (including no differences).
-
-
3.6 Allow
configuration so that a "client-side redirect" (i.e., one initiated
by the user agent, not the server) does not change
content except on explicit
user request. Allow the user to access the new content on demand
(e.g., by following a link or confirming a prompt). The user agent is not
required to provide these functionalities for client-side redirects that occur
instantaneously (i.e., when there is no delay before the new content is
retrieved). [Priority 2] Content only. (
Checkpoint 3.6)
-
- This checkpoint is a Priority 2 checkpoint in part because the author's
redirect implies that users aren't expected to use the content prior to the
redirect.
-
- Provide a configuration so that when the user navigates "back" through the
user agent history to a page with a client-side redirect, the user agent does
not re-execute the client-side redirect.
-
- Allow configuration to allow access on demand to new content even when the
client-side redirect has been specified by the author to be instantaneous.
-
- For Web content authors: refer to the HTTP/1.1 specification
[RFC2616] for information about using server-side redirect
mechanisms (instead of client-side redirects).
-
- 3.7 Allow
configuration not to render images. In this configuration, provide
an option to render a
placeholder in context for each unrendered image. When placeholders
are rendered, allow the user to view the original author-supplied content
associated with each placeholder.
[Priority 2] Content only. (Checkpoint
3.7)
- Note: See also checkpoint
3.8.
-
- See techniques for checkpoint 3.1.
-
- 3.8
Once the user has viewed the original author-supplied content associated with a
placeholder, allow the user to turn off the rendering of the
author-supplied content. [Priority 3]
Content only. (
Checkpoint 3.8)
- Note: For example, if the user agent
substitutes the author-supplied content for the placeholder in context, allow
the user to "toggle" between placeholder and the associated content. Or, if the
user agent renders the author-supplied content in a separate viewport, allow
the user to close that viewport. See checkpoint 3.2 and checkpoint 3.7.
-
- Allow the user to designate a placeholder and request to view the
associated content in a separate viewport (e.g., through the context menu),
leaving the placeholder in context. Per checkpoint 5.3, users are able to close the new
viewport.
-
In addition to the techniques below, refer also to the section on user control of style.
Checkpoints for visually rendered text
- 4.1
Allow global
configuration and control
over the reference size of rendered text, with an option to override reference
sizes specified by the author or user agent defaults. Allow the user to choose
from among the full range of font sizes supported by the
operating environment.
[Priority 1] Content only. (
Checkpoint 4.1)
- Note: The reference size of rendered
text corresponds to the default value of the CSS2 'font-size' property, which
is 'medium' (refer to CSS2 [CSS2], section 15.2.4). For example,
in HTML, this might be paragraph text. The default reference size of rendered
text may vary among user agents. User agents may offer different mechanisms to
allow control of the size of rendered text (e.g., font size control, zoom,
magnification, etc.). Refer, for example to the Scalable Vector Graphics
specification [SVG] for information about scalable
rendering.
-
- The choice of optimal techniques depends in part on which markup language
is being used. For instance, HTML user agents may allow the user to change the
font size of a particular piece of
text (e.g., by using CSS user style sheets) independent of other
content (e.g., images). Since the user agent can reflow the text after resizing
the font, the rendered text will become more legible without, for example,
distorting bitmap images. On the other hand, some languages, such as SVG, do
not allow text reflow, which means that changes to font size may cause rendered
text to overlap with other content, reducing accessibility. SVG is designed to
scale, making a zoom functionality the more natural technique for SVG user
agents satisfying this checkpoint.
-
- Inherit text size information from user preferences specified for the
operating environment.
- Use
operating environment magnification features.
- When scaling text, maintain size relationships among text of different
sizes.
- Implement the
'font-size' property in CSS ([CSS2], section 15.2.4).
-
- Allow the user to configure the text size on an element level (i.e., more
precisely than globally). User style sheets allow such detailed
configurations.
- Allow the user to configure the text size differently for different
scripts (i.e., writing systems).
-
-
4.2 Allow global configuration of the font family of all
rendered text, with an option to override font families specified by the author
or by user agent defaults. Allow the user to choose from among the full range
of font families supported by the
operating environment.
[Priority 1] Content only. (
Checkpoint 4.2)
- Note: For example, allow the user to
specify that all text is to be
rendered in a particular sans-serif font family. For text that cannot be rendered properly using the
user's preferred font family, the user agent may substitute an alternative font
family.
-
- Inherit font family information from user preferences specified for the
operating environment.
- Implement the
'font-family' property in CSS ([CSS2], section 15.2.2).
- Allow the user to override author-specified font families with differing
levels of detail. For instance, use font A in place of any sans-serif font and
font B in place of any serif font.
-
- Allow the user to configure font families on an element level (i.e., more
precisely than globally). User style sheets allow such detailed
configurations.
-
- 4.3
Allow global
configuration of the foreground and background color of all rendered
text, with an option to override foreground and background colors specified by
the author or user agent defaults. Allow the user to choose from among the full
range of colors supported by the
operating environment.
[Priority 1] Content only. (
Checkpoint 4.3)
- Note: User configuration of foreground
and background colors may inadvertently lead to the inability to distinguish
ordinary text from selected text, focused text, etc. See checkpoint 10.3 for more
information about highlight styles.
-
- Inherit foreground and background color information from user preferences
specified for the operating environment.
- Implement the
'color' and
'border-color' properties in CSS 2 ([CSS2], sections 14.1 and 8.5.2,
respectively).
- Implement the
'background-color' property (and other background properties) in CSS 2
([CSS2], section 14.2.1).
-
- Allow the user to specify minimal contrast between foreground and
background colors, adjusting colors dynamically to meet those
requirements.
-
Checkpoints for multimedia presentations and other
presentations that change continuously over time
- 4.4 Allow the user to slow the
presentation rate of audio and
animations (including video and animated images). For a visual
track, provide at least one setting between 40% and 60% of the
original speed. For a prerecorded
audio track including
audio-only presentations, provide at least one setting between 75%
and 80% of the original speed. When the user agent allows the user to slow the
visual track of a synchronized multimedia presentation to between 100% and 80%
of its original speed, synchronize the visual and audio tracks. Below 80%, the
user agent is not required to render the audio
track. The user agent is not required to satisfy this checkpoint for
audio and animations whose
recognized role is to create a purely stylistic effect. [Priority 1] Content only. (Checkpoint
4.4)
- Note: Purely stylistic effects include background sounds,
decorative animated images, and effects caused by style sheets. The style
exception of this checkpoint is based on the assumption that authors have
satisfied the requirements of the "Web Content Accessibility Guidelines 1.0"
[WCAG10] not to convey information through style alone (e.g.,
through color alone or style sheets alone). See checkpoint 2.6 and checkpoint 4.7.
-
- Allowing the user to slow the presentation of audio and
animations will benefit individuals with specific learning
disabilities, cognitive disabilities, or individuals with newly acquired
sensory limitations (such as a person who is newly blind and learning to use a
screen reader). The same feature will benefit individuals who have beginning
familiarity with a natural
language. Slowing one track (e.g., video) may make it harder for a
user to understand another synchronized track (e.g., audio), but if the user
can understand content after two passes, this is better than not being able to
understand it at all.
- Some formats (e.g., streaming formats), might not enable the user agent to
slow down playback and would thus be subject to applicability.
-
- When changing the rate of audio, avoid pitch distortion.
- HTML 4 [HTML4], background animations may
be specified with the deprecated
background
attribute.
- The
SMIL 2.0 Time Manipulations Module ([SMIL20], chapter 11) defines the
speed
attribute, which can be used to change the playback rate (as
well as forward or reverse direction) of any animation.
- Authors sometimes specify background sounds with the "bgsound" attribute.
Note: This attribute is not part of
HTML 4 [HTML4].
-
- Allowing the user to speed up audio is also useful. For example, some users
who access content serially benefit from the ability to speed up audio.
-
- Refer to variable playback speed techniques used for Digital Talking Books
[TALKINGBOOKS].
-
- 4.5 Allow the user to stop, pause,
resume, fast advance, and fast reverse audio and
animations (including video and animated images) that last three or
more seconds at their default playback rate. The user agent is not required to
satisfy this checkpoint for audio and animations whose
recognized role is to create a purely stylistic effect. The user
agent is not required to play synchronized audio during fast advance or reverse
of animations (though doing so may help orient the user). [Priority 1] Content only. (Checkpoint
4.5)
- Note: See
checkpoint 4.4 for more information about the exception for purely
stylistic effects. This checkpoint applies to content that is either rendered
automatically or on request from the user. The requirement of this checkpoint
is for control of each source of audio and animation that is
recognized as distinct. Respect synchronization cues per checkpoint 2.6.
-
- Some formats (e.g., streaming formats), might not enable the user agent to
fast advance or fast reverse content and would thus be subject to
applicability.
-
- Allow the user to advance or rewind the presentation in increments. This is
particularly valuable to users with physical disabilities who may not have fine
control over advance and rewind functionalities. Allow users to configure the
size of the increments.
- If buttons are used to control advance and rewind, make the advance/rewind
distances proportional to the time the user activates the button. After a
certain delay, accelerate the advance/rewind.
- The
SMIL 2.0 Time Manipulations Module ([SMIL20], chapter 11) defines the
speed
attribute, which can be used to change the playback
direction (forward or reverse) of any animation. See also the
accelerate
and decelerate
attributes.
- Some content lends itself to different forward and reverse functionalities.
For instance, compact disk players often let listeners fast forward and
reverse, but also skip to the next or previous song.
-
- The user agent should display time codes or represent otherwise position in
content to orient the user.
- Apply techniques for changing audio speed without introducing
distortion.
-
- Refer to fast advance and fast reverse techniques used for Digital Talking
Books [TALKINGBOOKS].
- Home Page Reader [HPR] lets users insert bookmarks in
presentations.
-
- 4.6 For graphical
viewports, allow the user to position text
transcripts, collated text transcripts, and captions
in the viewport. Allow the user to choose from among at least the range of
positions available to the author (e.g., the range of positions allowed by the
markup or style language). [Priority 1]
Content only. (Checkpoint
4.6)
-
- Some users need to be able to position captions, etc. so that they do not
obscure other content or are not obscured by other content. Other users (e.g.,
users with screen magnifiers or who have other visual disabilities) require
pieces of content to be in a particular relation to one another, even if this
means that some content will obscure other content.
-
- User agents should implement the positioning features of the employed
markup or style sheet language. Even when a markup language does not explicitly
allow positioning, when a user agent can recognize distinct text
transcripts, collated text transcripts, or captions,
the user agent should allow the user to reposition them. User agents are not
required to allow repositioning when the captions, etc. cannot be separated
from other media (e.g., the captions are part of the video track).
- For the purpose of applying this clause, SMIL 1.0
[SMIL] user agents should recognize as captions any media object
whose reference from SMIL is guarded by the '
system-captions
' test
attribute.
- Implement the CSS 2
'position' property ([CSS2], section 9.3.1).
- Allow the user to choose whether captions appear at the bottom or top of
the video area or in other positions. Currently authors may place captions
overlying the video or in a separate box. Captions prevent users from being
able to view other information in the video or on other parts of the screen,
making it necessary to move the captions in order to view all content at once.
In addition, some users will find captions easier to read if they can place
them in a location best suited to their reading style.
- Allow users to configure a general preference for caption position and to
be able to fine tune specific cases. For example, the user may want the
captions to be in front of and below the rest of the presentation.
- Allow the user to drag and drop the captions to a place on the screen. To
ensure device-independence, allow the user to enter the screen coordinates of
one corner of the caption.
- Do not require users to edit the source code of the presentation to achieve
the desired effect.
-
- Allow the user to position all parts of a presentation rather than trying
to identify captions specifically (i.e., solving the problem generally may be
easier than for captions alone).
- Allow the user to resize (graphically) the captions, etc.
-
-
4.7 Allow the user to slow the presentation rate of audio and
animations (including video and animated images) not covered by checkpoint 4.4. The same speed
percentage requirements of
checkpoint 4.4 apply. [Priority 2]
Content only. (
Checkpoint 4.7)
- Note: User agents automatically satisfy
this checkpoint if they satisfy
checkpoint 4.4 for all audio and animations.
-
- See the techniques for
checkpoint 4.4.
-
-
4.8 Allow the user to stop, pause, resume, fast advance, and fast
reverse audio and
animations (including video and animated images) not covered by checkpoint 4.5. [Priority 2] Content only. (
Checkpoint 4.8)
- Note: User agents automatically satisfy
this checkpoint if they satisfy checkpoint 4.5 for all audio and animations.
-
- See the techniques for
checkpoint 4.5.
-
Checkpoints for audio volume control
-
4.9 Allow global configuration and
control of the volume of all audio, with
an option to override audio volumes specified by the author or user agent
defaults. The user must be able to choose zero volume (i.e., silent).
[Priority 1] Content only. (
Checkpoint 4.9)
- Note: User agents should allow
configuration and control of volume through available
operating environment controls.
-
- Use audio control mechanisms provided by the
operating environment. Control of volume mix is particularly
important, and the user agent should provide easy access to those mechanisms
provided by the operating environment.
- Implement the CSS 2
'volume' property ([CSS2], section 19.2).
- Implement the
'display',
'play-during', and
'speak' properties in CSS 2 ([CSS2], sections 9.2.5, 19.6, and
19.5, respectively).
- Authors sometimes specify background sounds with the "bgsound" attribute.
Note: This attribute is not part of
HTML 4 [HTML4].
-
- Refer to guidelines for audio characteristics used for Digital Talking
Books [TALKINGBOOKS].
-
-
4.10 Allow independent
control of the volumes of distinct audio sources synchronized to
play simultaneously. [Priority 1] Content
only. (
Checkpoint 4.10)
- Note: Sounds that play at different times are
distinguishable and therefore independent control of their volumes is not
required by this checkpoint (since volume control required by checkpoint 4.9
suffices). The user agent should satisfy this checkpoint by allowing the user
to control independently the volumes of all distinct audio sources. The user
control required by this checkpoint includes the ability to override
author-specified volumes for the relevant sources of audio. See also checkpoint
4.12.
-
- There are at least three good reasons for strongly recommending that all
sounds be independently configurable, not just those synchronized to play
simultaneously.
- sounds that are not synchronized may end up playing simultaneously;
- if the user cannot anticipate when a sound will play, the user cannot
adjust the global volume control at appropriate times to affect this
sound;
- it is extremely inconvenient to have to adjust the global volume
frequently.
-
- For each source of audio recognized as distinct, allow the user to control
the volume using the same user interface used to satisfy the requirements of checkpoint 4.5.
-
Checkpoints for synthesized speech
See also techniques for synthesized
speech.
-
4.11 Allow
configuration and control of
the synthesized speech rate, according to the full range offered by the speech
synthesizer. [Priority 1] Content only. (
Checkpoint 4.11)
- Note: The range of speech rates offered
by the speech synthesizer may depend on natural language.
-
- For example, many speech synthesizers offer a range for English speech of
120 - 500 words per minute or more. The user should be able to increase or
decrease the speech rate in convenient increments (e.g., in large steps, then
in small steps for finer control).
- User agents may allow different speech rate configurations for different
natural languages. For example, this may be implemented with CSS2 style sheets
using the :lang
pseudo-class ([CSS2], section 5.11.4).
- Use synthesized speech mechanisms provided by the
operating environment.
- Implement the CSS 2
'speech-rate' property ([CSS2], section 19.8).
-
- Content may include commands that are interpreted by a speech engine to
change the speech rate (or control other speech parameters). This checkpoint
does not require the user agent to allow the user to override author-specified
speech rate changes (e.g., by transforming or otherwise stripping out these
commands before passing on the content to the speech engine). Speech engines
themselves may allow user override of author-specified speech rate changes. For
these such speech engines, the user agent should ensure access to this feature
as part of satisfying this checkpoint.
-
-
4.12 Allow control of
the synthesized speech volume, independent of other sources of audio. [Priority 1] Content only. (
Checkpoint 4.12)
- Note: The user control required by this checkpoint
includes the ability to override author-specified speech volume. See also checkpoint
4.10.
-
- The user agent should allow the user to make synthesized speech louder and
softer than other audio sources.
- Use synthesized speech mechanisms provided by the
operating environment.
- Implement the CSS 2
'volume' property ([CSS2], section 19.2).
-
- 4.13 Allow
configuration of speech characteristics according to the full range
of values offered by the speech synthesizer.
[Priority 1] Content only. (
Checkpoint 4.13)
- Note: Some speech synthesizers allow
users to choose values for speech characteristics at a higher abstraction
layer, i.e., by choosing from present options that group several
characteristics. Some typical options one might encounter include: "adult male
voice", "female child voice", "robot voice", "pitch", "stress", etc. Ranges for
values may vary among speech synthesizers.
-
- Use synthesized speech mechanisms provided by the
operating environment.
- One example of a speech API is Microsoft's Speech Application
Programming Interface [SAPI].
-
-
- For information about these speech characteristics, please refer to
descriptions in section 19.8 of Cascading Style Sheets Level 2
[CSS2].
-
-
4.14 Allow
configuration of the following speech characteristics: pitch, pitch
range, stress, richness. Pitch refers to the average frequency of the speaking
voice. Pitch range specifies a variation in average frequency. Stress refers to
the height of "local peaks" in the intonation contour of the voice. Richness
refers to the richness or brightness of the voice.
[Priority 2] Content only. (
Checkpoint 4.14)
- Note: This checkpoint is more specific
than checkpoint
4.13: it requires support for the voice characteristics listed. Definitions
for these characteristics are taken from section 19 of the Cascading Style
Sheets Level 2 Recommendation [CSS2]; please refer to that
specification for additional
informative descriptions. Some speech synthesizers allow users to
choose values for speech characteristics at a higher abstraction layer, i.e.,
by choosing from present options distinguished by "gender", "age", "accent",
etc. Ranges of values may vary among speech synthesizers.
-
- See
checkpoint 4.13.
-
-
4.15 Provide support for
user-defined extensions to the speech dictionary, as well as the following
functionalities: spell-out (spell text one character at a time or according to
language-dependent pronunciation rules), speak-numeral (speak a numeral as
individual digits or as a full number), and speak-punctuation (speak
punctuation literally or render as natural pauses).
[Priority 2] Content only. (
Checkpoint 4.15)
- Note: Definitions for the
functionalities listed are taken from section 19 of the Cascading Style Sheets
Level 2 Recommendation [CSS2]; please refer to that
specification for additional
informative descriptions.
-
-
-
- For information about these functionalities, please refer to descriptions
in section 19.8 of Cascading Style Sheets Level 2
[CSS2].
-
Checkpoints related to style sheets
- 4.16
For user agents that support
style sheets, allow the user to choose from (and apply) available
author and user style
sheets or to ignore them.
[Priority 1] Both content and user agent. (
Checkpoint 4.16)
- 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.
-
- For HTML [HTML4], make available "class" and
"id" information so that users can override styles.
- Implement user style
sheets.
- Implement the
"!important" semantics of CSS 2 ([CSS2], section 6.4.2).
-
- For information about how alternative style sheets are specified in HTML 4
[HTML4], please refer to
section 14.3.1.
- For information about how alternative style sheets are specified in XML 1.0
[XML], please refer to "Associating Style Sheets with XML documents
Version 1.0" [XMLSTYLE].
-
Checkpoints
-
5.1 Allow
configuration so that the
current focus does not move automatically to viewports
that open without explicit
user request. Configuration is not required if the current focus can
only ever be moved by explicit user request.
[Priority 2] Both content and user agent. (
Checkpoint 5.1)
- Note: For example, allow configuration
so that neither the current
focus nor the pointing device jump automatically to a viewport that
opens without explicit user request.
-
- Moving the focus automatically to a new viewport, this may disorient users
with cognitive disabilities or who are blind, and it may be difficult to
restore the previous point of regard.
-
- Allow the user to configure how the current
focus changes when a new viewport opens. For instance, the user
might choose between these two options:
- Do not change the focus when a viewport opens, but alert the user (e.g.,
with a beep, flash, and text message on the status bar). Allow the user to
navigate directly to the new window upon demand.
- Change the focus when a window opens and use a subtle alert (e.g., a beep,
flash, and text message
on the status bar) to indicate that the focus has changed.
- If a new viewport
or prompt appears but focus does not move to it, alert assistive technologies
(per checkpoint 6.5) so that they
may discreetly inform the user.
- When a viewport is duplicated, the focus in the new viewport should
initially be the same as the focus in the original viewport. Duplicate
viewports allow users to navigate content (e.g., in search of some information)
in one viewport while allowing the user to return with little effort to the
point of regard in the duplicate viewport. There are other techniques for
accomplishing this (e.g., "registers" in Emacs).
- In JavaScript, the focus may be changed with
myWindow.focus();
- For user agents that implement CSS 2
[CSS2], the following rule will generate a message to the user at
the beginning of link text for links that are meant to open new windows when
followed:
A[target=_blank]:before{content:"Open new window"}
-
- The user agent may also allow configuration about whether the pointing
device moves automatically to windows that open without an explicit user
request.
-
- 5.2 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. [Priority 2] Both content and
user agent. (Checkpoint
5.2)
-
- The alert is important to ensure that the user realizes a new viewport has
opened; the new viewport may be hidden by the viewport configured to remain on
top.
- In most operating environments, the viewport with focus is generally the
viewport "on top". In some environments, it's possible to allow a viewport that
is not on top to have focus.
-
- The user agent may also allow configuration about whether the viewport
designated by the pointing device always remains on top.
-
- 5.3 Allow
configuration so that viewports only open on explicit
user request. In this configuration, instead of opening a viewport
automatically, alert the user and allow the user to open it on demand (e.g., by
following a link or confirming a prompt). Allow the user to close viewports. If
a viewport (e.g., a frame set) contains other viewports, these requirements
only apply to the outermost container viewport.
[Priority 2] Both content and user agent. (Checkpoint
5.3)
- Note: User creation of a new viewport (e.g., empty or with
a new resource loaded) through the user agent's user interface constitutes an
explicit user request. See also checkpoint 5.1 (for control over changes of focus when a
viewport opens) and checkpoint 6.5
(for programmatic alert of changes to the user interface).
-
- Navigation of multiple open viewports may be difficult for some users who
navigate viewports serially (e.g., users with visual or physical disabilities)
and for some users with cognitive disabilities (who may be disoriented).
-
- For HTML [HTML4], allow the user to control
the process of opening a document in a new "target" frame or a viewport created
by a script. For example, for
target="_blank"
, open the window
according to the user's preference.
- For SMIL [SMIL], allow the user to control
viewports created with the "
new
" value of the "show
"
attribute.
- In JavaScript, windows may be opened with:
myWindow.open("example.com", "My New Window");
myWindow.showHelp(URI);
-
- 5.4 Allow
configuration to prompt the
user to confirm (or cancel) any form submission that is not caused by an explicit
user request to activate a
form submit control. [Priority 2] Content
only. (Checkpoint
5.4)
- Note: For example, do not submit a form
automatically when a menu option is selected, when all fields of a form have
been filled out, or when a "mouseover" or "change" event event occurs. The user agent may satisfy this
checkpoint by prompting
the user to confirm all form submissions.
-
- In HTML 4 [HTML4], form submit controls are
the
INPUT element (section 17.4) with
type="submit"
and
type="image"
, and the
BUTTON element (section 17.5) with type="submit"
.
- Allow the user to configure script-based submission (e.g., form submission
accomplished through an "onChange" event). For instance, allow these settings:
- Do not allow script-based submission.
- Allow script-based submission after confirmation from the user.
- Allow script-based submission without prompting the user (but not by
default).
- Authors may write scripts that submit a form when particular events occur (e.g., "onchange" events). Be
aware of this type of practice:
<SELECT NAME="condition" onchange="switchpage(this)">
As soon as the user attempts to navigate the menu, the "switchpage" function
opens a document in a new viewport. Try to avoid orientation problems that may
be caused by scripts bound to form controls.
- Be aware that users may inadvertently pressing the Return or
Enter key and accidentally submit a form.
- In JavaScript, a form may be submitted with:
document.form[0].submit();
document.all.mySubmitButton.click();
- Generate an explicit form submit button when the author has not provided
one.
-
- Users who navigate a document serially may think that the submit button in
a form is the "last" control
they need to complete before submitting the form. Therefore, for forms in which
additional controls follow a submit button, if those controls have not been
completed, inform the user and ask for confirmation (or completion) before
submission.
- For forms, allow users to search for
controls that need to be changed by the user before submitting the
form.
-
- 5.5 Allow
configuration to prompt the
user to confirm (or cancel) any payment that results from activation
of a fee link.
[Priority 2] Content only. (Checkpoint
5.5)
-
- Allow the user to configure the user agent to prompt for payments above a
certain amount (including any payment).
- Warn the user that even in this configuration, the user agent may not be
able to recognize some payment mechanisms.
-
- 5.6
Allow
configuration to prompt the
user to confirm (or cancel) closing any viewport that starts to close without
explicit
user request. [Priority 3] Both
content and user agent. (
Checkpoint 5.6)
-
- In JavaScript, windows may be closed with
myWindow.close();
-
Checkpoints
- 6.1 Provide programmatic read access to
HTML and XML
content by conforming to the following
modules of the W3C Document Object Model DOM Level 2 Core Specification [DOM2CORE] and exporting the
interfaces they define: (1) the Core module for HTML; (2) the Core and XML
modules for XML. [Priority 1] Content only.
(Checkpoint
6.1)
- Note: Please refer to the "Document
Object Model (DOM) Level 2 Core Specification"
[DOM2CORE] for information about HTML and
XML versions covered.
-
- The primary reason for requiring user agents to implement the DOM is that
this gives assistive technologies access to the original structure of the
document. For example, this means that assistive technologies that render
content as speech are not required to construct the speech view by "reverse
engineering" a graphical view. Direct access to the structure allows the
assistive technologies to render content in a manner best suited to a
particular output device. This does not mean that assistive technologies should
be prevented from having access to the rendering of the conforming user agent;
simply that they not be required to depend entirely on it. In fact, speech user
agents may wish to synchronize a graphical view with a speech view.
- Note that the W3C DOM is designed to be used on a server as well as a
client and does not address some user interface-specific information.
-
- Refer to a listing of DOM implementations at the Open
Directory Project [ODP-DOM].
-
- See the appendix on loading assistive
technologies for DOM access.
-
- For information about rapid access to Internet Explorer's
[IE-WIN] DOM through COM, refer to
[BHO].
- Refer to the DirectDOM Java implementation of the DOM
[DIRECTDOM].
-
- 6.2 If the user can modify
HTML and XML content
through the user
interface, provide the same functionality programmatically by
conforming to the following modules of the W3C Document Object Model DOM Level 2 Core Specification [DOM2CORE] and exporting the
interfaces they define: (1) the Core module for HTML; (2) the Core and XML
modules for XML. [Priority 1] Content only.
(Checkpoint
6.2)
- Note: For example, if the user
interface allows users to complete HTML forms, this must
also be possible through the required DOM APIs. Please refer to the "Document Object
Model (DOM) Level 2 Core Specification"
[DOM2CORE] for information about HTML and
XML versions covered.
-
- Allowing assistive technologies write access through the DOM allows them
to:
- modify the attribute list of a document and thus add information into the
document object that will not be rendered by the user agent.
- add entire nodes to the document that are specific to the assistive
technologies and that may not be rendered by a user agent unaware of their
function.
- The ability to write to the DOM can improve performance for the assistive
technology. For example, if an assistive technology has already traversed a
portion of the document object and knows that a section (e.g., a style element)
could not be rendered, it can mark this section "to be skipped".
- Another benefit is to add information necessary for audio rendering but
that would not be stored directly in the DOM during parsing (e.g., numbers in
an ordered list). An assistive technology component can add numeric information
to the document object. The assistive technology can also mark a subtree as
having been traversed and updated, to eliminate recalculating the information
the next time the user visits the subtree.
-
- See also techniques for
checkpoint 6.1.
-
- 6.3 For markup languages other than
HTML and XML, provide programmatic access
to content
using standard APIs (e.g., platform-independent APIs and
standard APIs for the
operating environment). If standard
APIs do not exist, provide programmatic
access through publicly documented
APIs.
[Priority 1] Content only. (Checkpoint
6.3)
- Note: This checkpoint addresses content
not covered by checkpoints
checkpoint 6.1 and
checkpoint 6.2.
-
- Some examples of markup languages covered by this checkpoint include
SGML
applications other than HTML and
RTF, and TeX.
-
- See techniques for checkpoint
6.4.
-
- Some public APIs that enable access include:
- Microsoft Active Accessibility ([MSAA]) in Windows 95/98/NT
versions.
- Sun Microsystems Java Accessibility API ([JAVAAPI]) in Java JDK. If the
user agent supports Java applets and provides a Java Virtual Machine to run
them, the user agent should support the proper loading and operation of a Java
native assistive technology. This assistive technology can provide access to
the applet as defined by Java accessibility standards.
-
- 6.4 Provide programmatic read and write
access to user
agent user interface controls using standard APIs. If standard APIs do not exist, provide programmatic access
through publicly documented APIs.
[Priority 1] User agent only. (Checkpoint
6.4)
- Note: Per checkpoint 6.6, provide
programmatic access through standard APIs (e.g.,
platform-independent APIs such as the W3C DOM; standard
APIs defined for a specific operating system; and
conventions for programming languages, plug-ins, virtual machine environments,
etc.). This checkpoint requires user agents to provide programmatic access even
in the absence of a standard API for doing so.
-
- Use standard operating environment) APIs
that support accessibility by providing a bridge between the standard user
interface supported by the operating operating and alternative user interfaces
developed by assistive
technologies. User agents that implement these
APIs are generally more compatible with assistive technologies and
provide accessibility at no extra cost.
- Use standard user
interface controls. Third-party assistive technology developers are
more likely able to access standard controls than custom
controls. If you use custom controls,
review them for accessibility and compatibility with third-party assistive
technology. Ensure that they provide accessibility information through an API
as is done for the standard controls.
- Make use of operating environment-level features. See the
appendix of accessibility features
for some common operating systems.
-
- Some public accessibility APIs include:
- Microsoft Active Accessibility ([MSAA]) in Windows 95/98/NT
versions.
- Sun Microsystems Java Accessibility API ([JAVAAPI]) in Java JDK. If the
user agent supports Java applets and provides a Java Virtual Machine to run
them, the user agent should support the proper loading and operation of a Java
native assistive technology. This assistive technology can provide access to
the applet as defined by Java accessibility standards.
- For information about rapid access to Internet Explorer's
[IE-WIN] DOM through COM, refer to Browser Helper Objects
[BHO].
-
- 6.5 Using standard APIs, provide programmatic alert of changes to
content, user
interface controls,
selection, content
focus, and user
interface focus. If standard
APIs do not exist, provide programmatic
alert through publicly documented
APIs.
[Priority 1] Both content and user agent. (Checkpoint
6.5)
- Note: For instance, when user
interaction in one frame causes automatic changes to content in another,
provide programmatic alert through standard APIs. Use the standard APIs required by the checkpoints of guideline 6.
-
- Write output to and take input from standard
operating environment APIs rather than directly
from hardware controls. This will enable the input/output to be redirected from
or to assistive technology devices – for example, screen readers and
braille displays often redirect output (or copy it) to a serial port, while
many devices provide character input, or mimic mouse functionality. The use of
generic APIs makes this feasible in a way that allows for interoperability of
the assistive technology with a range of applications.
- Alert the user when an action in one frame causes the content of another
frame to change. Allow the user to navigate with little effort to the frame(s)
that changed.
-
- Refer to "mutation events" in "Document Object Model (DOM) Level 2 Events
Specification" [DOM2EVENTS]. This DOM Level 2
specification allows assistive technologies to be informed of changes to the
document tree.
- Refer also to information about monitoring HTML events
through the document
object model in Internet Explorer
[IE-WIN].
-
- 6.6
Implement standard accessibility APIs (e.g., of the
operating environment). Where these APIs do not enable the user
agent to satisfy the requirements of this document, use the
standard input and output APIs of the
operating environment. [Priority 1] Both
content and user agent. (
Checkpoint 6.6)
- Note: Accessibility APIs enable
assistive technologies to monitor input and output events. As part of
satisfying this checkpoint, the user agent needs to ensure that text content is available as text through these
APIs (and not, for example, as a series of strokes drawn on the screen).
-
- Operating system and application frameworks provide standard mechanisms for
communication with input devices. In the case of Windows, OS/2, the X Windows
System, and Mac OS, the window manager provides Graphical User Interface
(GUI) applications with this information through the
messaging queue. In the case of non-GUI applications, the compiler run-time
libraries provide standard mechanisms for receiving keyboard input in the case
of desktop operating systems. If you use an application framework such as the
Microsoft Foundation Classes, the framework used should support the same
standard input mechanisms.
- Do not communicate directly with an input device; this may circumvent
operating environment messaging. For instance, in Windows, do not
open the keyboard device driver directly. It is often the case that the
windowing system needs to change the form and method for processing standard
input mechanisms for proper application coexistence within the user interface
framework.
- Do not implement your own input device event queue mechanism; this may
circumvent operating environment messaging. Some assistive technologies use
standard system facilities for simulating keyboard and mouse events. From the
application's perspective, these events are no different than those generated
by the user's actions. The "Journal Playback Hooks" (in both OS/2 and Windows)
are one example of an application that feeds the standard event queues. For an
example of a standard event queue mechanism, refer to the "Carbon Event Manager
Preliminary API Reference" [APPLE-HI].
-
Operating environments provide standard mechanisms for using
standard output devices. In the case of common desktop operating systems such
as Windows, OS/2, and Mac OS, standard
APIs are provided for writing to the
display and the multimedia subsystems.
- Avoid rendering text in the
form of a bitmap before transferring to the screen, since some screen readers
rely on the user agent's offscreen model. An offscreen model is rendered
content created by an assistive technology that is based on the rendered
content of another user agent. Assistive technologies that rely on
an offscreen model generally construct it by intercepting standard
Operating environments drawing calls. For example, in the case of
display drivers, some screen readers are designed to monitor what is drawn on
the screen by hooking drawing calls at different points in the drawing process.
While knowing about the user agent's formatting may provide some useful
information to assistive technologies, this document encourages assistive
technologies to access to content directly through published APIs (such as the
DOM) rather than via a particular rendering.
- Common operating environment two-dimensional graphics engines and drawing
libraries provide functions for drawing
text to the screen. Examples of this are the Graphics Device
Interface (GDI) for Windows, Graphics Programming Interface (GPI) for OS/2, and
the X library (XLIB) for the X Windows System or Motif.
- Do not communicate directly with an output device.
- Do not draw directly to the video frame buffer.
- Do not provide your own mechanism for generating pre-defined
operating environment sounds.
- When writing textual information in a GUI
operating environment, use standard operating environment APIs for drawing text.
- Use
operating environment resources for rendering audio information.
When doing so, do not take exclusive control of system audio resources. This
could prevent an assistive technology such as a screen reader from speaking if
they use software text-to-speech conversion. Also, in operating environments
like Windows, a set of standard audio sound resources are provided to support
standard sounds such as alerts. These
preset sounds are used to trigger
SoundSentry graphical cues when a problem occurs; this benefits users with
hearing disabilities. These cues may be manifested by flashing the desktop,
active caption bar, or current viewport. It is important to use the standard
mechanisms to generate audio feedback so that operating environments or special
assistive technologies can add additional functionality for users with hearing
disabilities.
-
- Microsoft Active Accessibility ([MSAA]) is the standard accessibility
API for the Windows 95/98/NT operating systems.
- Sun Microsystems Java Accessibility API ([JAVAAPI]) in the Java JDK is the
standard accessibility API for the Java environment.
-
- 6.7
Implement the operating environment's standard
APIs for the keyboard. If standard APIs for the keyboard do not exist, implement
publicly documented APIs for the keyboard.
[Priority 1] User agent only. (Checkpoint
6.7)
- Note: An operating environment may define more than one
standard API for the keyboard. For instance, for Japanese and Chinese, input
may be processed in two stages, with an API for each.
-
- Account for author-specified keyboard bindings, such as those specified by
"accesskey" attribute in HTML 4 ([HTML4], section 17.11.2).
- Test that all user
interface components may be operable by software or devices that
emulate a keyboard. Use SerialKeys and/or
voice recognition software to test keyboard event emulation.
-
- Enhance the functionality of standard operating environment controls to
improve accessibility where none is provided by responding to standard keyboard
input mechanisms. For example provide keyboard navigation to menus and dialog
box controls in the Apple Macintosh operating system. Another example is the
Java Foundation Classes, where internal frames do not provide a keyboard
mechanism to give them focus. In this case, you will need to add keyboard
activation through the standard keyboard activation facility for Abstract
Window Toolkit components.
-
- Apply the techniques for checkpoint 1.1 to the keyboard.
-
- 6.8 For an API implemented to satisfy
requirements of this document, support the character
encodings required for that API.
[Priority 1] Both content and user agent. (Checkpoint
6.8)
- Note: Support for character encodings is important so that
text is not "broken" when communicated to assistive technologies. For example,
the DOM Level 2 Core Specification [DOM2CORE], section 1.1.5
requires that the
DOMString
type be encoded using UTF-16. This
checkpoint is an important special case of the other API
requirements of this document.
-
- The list of character encodings that any conforming implementation of Java
version 1.3 [JAVA13] must support is: US-ASCII,
ISO-8859-1, UTF-8, UTF-16BE, UTF-16LE, and UTF-16.
- MSAA [MSAA] relies on the
COM interface, which in turn relies on Unicode
[UNICODE], which means that for MSAA a user agent must support
UTF-16. From Chapter 3 of the COM documentation, on interfaces, entitled "Interface Binary Standard":
Finally, and quite significantly, all strings passed through all COM
interfaces (and, at least on Microsoft platforms, all COM APIs) are Unicode
strings. There simply is no other reasonable way to get interoperable objects
in the face of (i) location transparency, and (ii) a high-efficiency object
architecture that doesn't in all cases intervene system-provided code between
client and server. Further, this burden is in practice not large."
-
- 6.9 For user agents that implement
Cascading Style Sheets (CSS), provide programmatic access to
those style sheets by conforming to the CSS module of the W3C Document Object
Model (DOM) Level 2 Style
Specification [DOM2STYLE] and exporting the
interfaces it defines. [Priority 2] Content
only. (Checkpoint
6.9)
- Note: As of the publication of this
document, Cascading Style Sheets (CSS) are defined by CSS
Level 1 [CSS1] and CSS Level 2
[CSS2]. Please refer to the "Document Object Model (DOM) Level 2
Style Specification"
[DOM2STYLE] for information about CSS versions
covered.
-
- See techniques for
checkpoint 6.1.
-
- 6.10 Ensure that programmatic exchanges
proceed in a timely manner. [Priority 2]
Both content and user agent. (Checkpoint
6.10)
- 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.
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.
-
- Alert the user when information may be lost due to communication
delays.
-
- Please see the appendix that explains how to load assistive technologies for DOM
access.
-
Checkpoints
-
7.1 Follow operating environment conventions that benefit
accessibility when
implementing the
selection, content
focus, and user
interface focus. [Priority 1]
User agent only. (
Checkpoint 7.1)
- Note: This checkpoint is an important special case of checkpoint 7.3. See also checkpoint 9.1.
-
- See techniques for checkpoint
7.3.
-
- Refer to
Selection and Partial Selection of DOM Level 2 ([DOM2RANGE], section
2.2.2).
- For information about focus in the Motif environment (under X Windows),
refer to the OSF/Motif Style Guide [MOTIF].
-
-
7.2 Ensure that default input
configurations do not interfere with
operating environment accessibility conventions. [Priority 1] User agent only. (
Checkpoint 7.2)
- Note: In particular, default
configurations should not interfere with operating conventions for keyboard
accessibility. See also
checkpoint 11.5.
-
- The default configuration should not include
"Alt-F4",
"Control-Alt-Delete", or other combinations
that have reserved meanings in a given operating environment.
- Clearly document any default configurations that depart from operating
environment conventions.
-
- Some reserved keyboard bindings are listed in the appendix on accessibility features of some operating
systems.
-
- 7.3 Follow
operating environment conventions that benefit accessibility. In
particular, follow conventions that benefit accessibility for user
interface design, keyboard configuration, product installation, and
documentation. [Priority 2] User
agent only. (Checkpoint
7.3)
- Note: Operating environment conventions that benefit
accessibility are those described in this document and in platform-specific
accessibility guidelines.
-
- Much of the rationale behind the content requirements of User Agent
Accessibility Guidelines 1.0 also makes sense for the user
agent user interface (e.g., allow the user to turn off any blinking
or moving user interface components).
-
- Follow operating environment conventions for loading assistive
technologies. See the appendix on loading
assistive technologies for DOM access for information about how an
assistive technology developer can load its software into a Java Virtual
Machine.
- Inherit
operating environment settings related to accessibility (e.g., for
fonts, colors, natural
language preferences, input configurations, etc.).
- Ensure that any online services (e.g., automated update facilities,
download-and-install functionalities, sniff-and-fill forms, etc.) observe
relevant operating environment conventions concerning device independence and
accessibility (as well as the Web Content Accessibility Guidelines 1.0
[WCAG10]).
- Evaluate the standard interface controls on the target platform against any
built-in operating environment accessibility functions (see the appendix on accessibility features of some
operating systems). Ensure that the user agent operates properly with all
these functions. Here is a sample of features to consider:
- Microsoft Windows offers an accessibility function called "High Contrast".
Standard window classes and controls automatically support this setting.
However, applications created with custom classes or controls work with the
"GetSysColor" API to ensure compatibility with High Contrast.
- Apple Macintosh offers an accessibility function called "Sticky Keys".
Sticky Keys operate with keys the operating environment recognizes as modifier
keys, and therefore a custom control should not attempt to define a new
modifier key.
- Maintain consistency in the user interface between versions of the
software. Consistency is less important than improved general accessibility and
usability when implementing new features. However, developers should make
changes conservatively to the layout of user interface
controls, the behavior of existing
functionalities, and the default keyboard configuration.
-
- See techniques for
checkpoint 6.6, checkpoint
6.4, and checkpoint
7.2.
-
- Follow accessibility guidelines for specific platforms:
- "Macintosh Human Interface Guidelines"
[APPLE-HI]
- "IBM Guidelines for Writing Accessible Applications Using 100% Pure Java"
[JAVA-ACCESS].
- "An Inter-client Exchange (ICE) Rendezvous Mechanism for
X Window System Clients" [ICE-RAP].
- "Information for Developers About Microsoft Active Accessibility"
[MSAA].
- "The Inter-Client communication conventions manual"
[ICCCM].
- "Lotus Notes accessibility guidelines"
[NOTES-ACCESS].
- "Java accessibility guidelines and checklist" [JAVA-CHECKLIST].
- "The Java Tutorial. Trail: Creating a GUI with JFC/Swing"
[JAVA-TUT].
- "The Microsoft Windows Guidelines for Accessible Software Design"
[MS-SOFTWARE].
- Follow general guidelines for producing accessible software:
- "Accessibility for applications designers"
[MS-ENABLE].
- "Application Software Design Guidelines"
[TRACE-REF]. Refer also to "EZ ACCESS(tm) for electronic devices V
2.0 implementation guide" [TRACE-EZ] from the Trace
Research and Development Center.
- Articles and papers from Sun Microsystems about accessibility
[SUN-DESIGN].
- "EITAAC Desktop Software standards"
[EITAAC].
- "Requirements for Accessible Software Design"
[ED-DEPT].
- "Software Accessibility" [IBM-ACCESS].
- Towards Accessible Human-Computer Interaction"
[SUN-HCI].
- "What is Accessible Software" [WHAT-IS].
- Accessibility guidelines for Unix and X Window applications
[XGUIDELINES].
-
-
7.4 Follow operating environment conventions to indicate
the input
configuration. [Priority 2] User
agent only. (
Checkpoint 7.4)
- Note: For example, in some operating environments,
developers may specify which command sequence will activate a functionality so
that the standard user interface components display that binding. For example,
if a functionality is available from a menu, the letter of the activating key
may be underlined in the menu. This checkpoint is an important special case of
checkpoint 7.3. See also checkpoint
11.5.
-
- Use
operating environment conventions to indicate the current
configuration (e.g., in menus, indicate what key strokes will activate the
functionality, underline single keys that will work in conjunction with a key
such as Alt, etc.) These are conventions used by the Sun Java
Foundations Classes [JAVA-TUT] and Microsoft
Foundations Classes for Windows.
- Ensure that information about changes to the input configuration is
available in a device-independent manner (e.g., through visual and audio cues,
and through text).
- If the current configuration changes locally (e.g., a search prompt opens,
changing the keyboard mapping for the duration of the prompt), alert the
user.
- Named configurations are easier to remember. This is especially important
for people with certain types of cognitive disabilities. For example, if the
invocation of a search prompt changes the input configuration, the user may
remember more easily which key strokes are meaningful in search mode if alerted
that there is a "Search Mode". Context-sensitive help (if available) should
reflect the change in mode, and a list of keybindings for the current mode
should be readily available to the user.
-
- See input configuration
techniques.
-
Checkpoints
-
8.1 Implement the accessibility features of all
implemented specifications (markup languages, style sheet languages,
metadata languages, graphics formats, etc.). The accessibility features of a
specification are those identified as such and those that satisfy all
of the requirements of the "Web Content Accessibility Guidelines 1.0" [WCAG10].
[Priority 1] Content only. (
Checkpoint 8.1)
- Note: This checkpoint applies to both W3C-developed and
non-W3C specifications.
-
- Make obvious to users features that are known to benefit accessibility.
Make them easy to find in the user interface and in documentation.
- Some specifications include optional features (not required for conformance
to the specification). If an optional feature is likely to cause accessibility
problems, developers should either ensure that the user can turn off the
feature or they not implement the feature.
- Refer to the following list of accessibility features of HTML 4
[HTML4] (in addition to those described in techniques for checkpoint 2.1):
-
- Refer to the "Accessibility Features of CSS"
[CSS-ACCESS]. Note that CSS 2 includes properties for configuring
synthesized speech styles.
- Refer to the "Accessibility Features of SMIL"
[SMIL-ACCESS].
- Refer to the "Accessibility Features of SVG"
[SVG-ACCESS].
- For information about the Sun Microsystems Java Accessibility API in Java
JDK, refer to [JAVAAPI].
- For information about captioning for the Synchronized Accessible Multimedia
Interchange (SAMI), refer to
[SAMI].
-
- 8.2 Use and
conform to either (1) W3C Recommendations
when they are available and appropriate for a task, or (2) non-W3C
specifications that enable the creation of content that conforms to the Web
Content Accessibility Guidelines 1.0 [WCAG10] at any conformance level.
[Priority 2] Content only. (Checkpoint
8.2)
- Note: For instance, for markup, the
user agent may conform to
HTML 4 [HTML4], XHTML 1.0
[XHTML10], or XML 1.0 [XML].
For style sheets, the user agent may conform to CSS
([CSS1],
[CSS2]). For mathematics, the user agent may conform to MathML 2.0
[MATHML20]. For synchronized
multimedia, the user agent may conform to SMIL 1.0
[SMIL]. 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 requirement of this checkpoint is to conform to at least one
W3C Recommendation that is available and appropriate for a particular task, or
at least one non-W3C specification that allows the creation of content that
conforms to WCAG 1.0 [WCAG10]. For example, user agents
would satisfy this checkpoint by conforming to the Portable Network Graphics
1.0 specification [PNG] for raster images. In addition,
user agents may implement other image formats such as JPEG, GIF, etc. Each
specification defines what conformance means for that specification.
-
- If more than one version or level of a specification is appropriate for a
particular task, user agents are encouraged to conform to the latest version.
However, developers should consider implementing the version that best supports
accessibility, even if this is not the latest version.
- For reasons of backward compatibility, user agents should continue to
implement deprecated features of specifications. Information about deprecated
language features is generally part of the language's specification.
-
- The list of current W3C Recommendations and
other technical documents is available at
http://www.w3.org/TR/
.
- W3C make available validation services to promote the proper usage and
implementation of specifications. Refer to the:
- Information about PDF and accessibility is made available by Adobe
[ADOBE].
-
Checkpoints
- 9.1 Allow the user to make the selection
and focus of each
viewport
(including frames) the current selection and current
focus, respectively.
[Priority 1] User agent only. (Checkpoint
9.1)
- Note: For example, when all frames of a
frameset are displayed side-by-side, allow the user (via the keyboard) to move
the focus among
them.
-
- Some
operating environments provide a means to move the user
interface focus among all open windows using multiple input devices
(e.g., keyboard and mouse). This technique would suffice for switching among
user agent viewports that are separate windows.
-
- 9.2 Allow the user to move the content
focus to any enabled element in the viewport.
If the author has not specified a navigation order, allow at least forward
sequential navigation to each element, in document order. The user agent may
also include disabled
elements in the navigation order.
[Priority 1] Content only. (Checkpoint
9.2)
- Note: In addition to forward sequential
navigation, the user agent should also allow reverse sequential navigation.
This checkpoint is an important special case of checkpoint 9.8.
-
- Allow the user to move the content focus to each enabled element by
repeatedly pressing a single key. Many user agents today allow users to
navigate sequentially by repeating a key combination – for example, using
the Tab key for forward navigation and Shift-Tab for
reverse navigation. Because the Tab key is typically on one side of
the keyboard while arrow keys are located on the other, users should be allowed
to configure the user agent so that sequential navigation is possible with keys
that are physically closer to the arrow keys. See also checkpoint 11.3.
- Maintain a logical element navigation order. For instance, users may use
the keyboard to navigate among elements or element groups using the arrow keys
within a group of elements. One example of a group of elements is a set of
radio buttons. Users should be able to navigate to the group of buttons, then
be able to select each button in the group. Similarly, allow users to navigate
from table to table, but also among the cells within a given table (up, down,
left, right, etc.).
- Respect author-specified information about navigation order (e.g., the
"tabindex" attribute in HTML 4
[HTML4], section 17.11.1). Allow users to override the
author-specified navigation order (e.g., by offering an alphabetized view of
links or other orderings).
- The default sequential navigation order should respect the conventions of
the natural
language of the document. Thus, for most left-to-right languages,
the usual navigation order is top-to-bottom and left-to-right. For
right-to-left languages, the order would be top-to-bottom and
right-to-left.
- Implement the
':hover', ':active', and ':focus' pseudo-classes of CSS 2 ([CSS2], section 5.11.3). This allows
users to modify content focus presentation with user style sheets. Use them in
conjunction with the
CSS 2 ':before' pseudo-elements ([CSS2], section 5.12.3) to clearly
indicate that something is a link (e.g., 'A:before { content : "LINK:"
}').
- In Java, a component is part of the sequential navigation order when added
to a panel and its
isFocusTraversable
method returns true. A
component can be removed from the navigation order by extending the component,
overloading this method, and returning false.
-
-
- Provide other sequential navigation mechanisms for particular element types
or semantic units, e.g., "Find the next table" or "Find the previous form." For
more information about sequential navigation of form
controls and form submission, see
techniques for checkpoint
5.4.
- For graphical user agents (or any user agent offering a two-dimensional
display), navigation based not on document order but on layout may also benefit
the user. For example, allow the user to navigate up, down, left, and right to
the nearest rendered enabled link. This type of navigation may be particularly
useful when it is clear from the layout where the next navigation step will
take the user (e.g., grid layouts where it is clear what the next link to the
left or below will be).
- Excessive use of sequential navigation can reduce the usability of software
for both disabled and non-disabled users. Some useful types of direct
navigation include: navigation based on position (e.g., all links are numbered
by the user agent), navigation based on element content (e.g., the first letter
of
text content), direct navigation to a
table cell by its row/column position, and searching (e.g., based on form
control text, associated labels, or form control names).
-
-
9.3 For each state in a viewport's browsing history, maintain
information about the point of regard, content
focus, user
interface focus, and
selection. When the user returns to any state in the viewport
history, restore the saved values for all four of these state variables. [Priority 1] User agent only. (
Checkpoint 9.3)
- Note: For example, when the user uses
the "back" functionality, restore the four state variables.
-
- If the user agent allows the user to browse multimedia or
audio-only presentations, when the user leaves one presentation for
another, pause the presentation. When the user returns to a previous
presentation, allow the user to resume the presentation where it was paused
(i.e., return the point of
regard to the same place in space and time). Note:
This may be done for a presentation that is available "completely" but not for
a "live" stream or any part of a presentation that continues to run in the
background.
- Allow the user to configure whether leaving a viewport pauses a multimedia
presentation.
- If the user activates a broken link, leave the viewport where it is and
alert the user (e.g., in the status bar and with a graphical
or audio alert). Moving the viewport suggests that a link is not broken, which
may disorient the user.
- In JavaScript, the following may be used to change the Web resource in the
viewport, and navigate the history:
myWindow.home();
myWindow.forward();
myWindow.back();
myWindow.navigate("http://example.com/");
myWindow.history.back();
myWindow.history.forward();
myWindow.history.go( -2 );
location.href = "http://example.com/"
location.reload();
location.replace("http://example.com/");
-
- Restore the four state variables after the user refreshes the same
content.
-
- Refer to the HTTP/1.1 specification for information about history
mechanisms ([RFC2616], section 13.13).
-
- 9.4 For the element with content
focus, make available the list of input device event
handlers explicitly associated with the element. [Priority 2] Content only. (Checkpoint
9.4)
- Note: For example, allow the user to
query the element with content focus for the list of input device event
handlers, or add them directly to the serial navigation order. See checkpoint 1.2 for
information about activation of event handlers associated with the element with
focus.
-
- For HTML content, the left mouse button is generally the only mouse button
that is used to activate event handlers associated with mouse clicks.
-
- See checkpoint
1.2 for information about input device event handlers in HTML 4
[HTML4] and the Document Object Model (DOM) Level 2 Events
Specification [DOM2EVENTS].
-
-
9.5 Allow
configuration so that moving the content
focus to an enabled element does not automatically activate
any explicitly associated input device event
handlers. [Priority 2] Content
only. (
Checkpoint 9.5)
- Note: 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.
-
- First-time users of a page may want access to link text before deciding
whether to follow (activate) the link. More experienced users of a page might
prefer to follow the link directly, without the intervening content focus
step.
-
- Allow the following configurations:
- On invocation of the input binding, move focus to the associated enabled
element, but do not activate it.
- On invocation of the input binding, move focus to the associated enabled
element and prompt the user with information that will allow the user to decide
whether to activate the element (e.g., link title or text). Allow the user to
suppress future prompts for this particular input binding.
- On invocation of the input binding, move focus to the associated enabled
element and activate it.
-
- 9.6 Allow the user to move the content
focus to any enabled element in the viewport.
If the author has not specified a navigation order, allow at least forward and
reverse sequential navigation to each element, in document order. The user
agent must not include disabled elements in the navigation order.
[Priority 2] Content only. (Checkpoint
9.6)
- Note: This checkpoint is a special case
of checkpoint 9.2.
-
- Apply the techniques of
checkpoint 9.2 to enabled elements only.
-
- 9.7 Allow the user to search within rendered text
content for a sequence of characters from the
document character set. Allow the user to start a forward search (in
document order) from any selected or focused location in content. When there is
a match (1) move the viewport so that the matched text content is within it,
and (2) allow the user to search for the next instance of the text from the
location of the match. Alert the user when there is no match, when the search
reaches the end of content, and prior to any wrapping. Provide a
case-insensitive search option for text in
scripts (i.e., writing systems) where case is significant. [Priority 2] Content only. (Checkpoint
9.7)
- Note: If the user has not indicated a start position for
the search, the search should start from the beginning of content. Use
operating environments conventions for indicating the result of a
search (e.g., selection
or content
focus). A wrapping search is one that restarts automatically at the
beginning of content once the end of content has been reached.
-
- Use the selection or focus to indicate found text. This will provide
assistive technologies with access to the text.
- Allow users to search all views (e.g., including views of the text
source).
- For extremely small viewports or extremely long matches, the entire matched
text content may not fit within the viewport. In this case, developers may move
the viewport to encompass the initial part of the matched content.
- The search string input method should follow
operating environment conventions (e.g., for international character
input).
- When the point of regard depends on time (e.g., for audio viewports), the
user needs to be able to search through content that will be available through
that viewport. This is analogous to content rendered graphically that is
reachable by scrolling.
- For frames, allow users to search for content in all frames, without having
to be in a particular frame.
- For multimedia presentations, allow users to search and examine
time-dependent media elements and links in a time-independent manner. For
example, present a static list of time-dependent links.
- Allow users to search the element content of form controls (where
applicable) and any label text.
- When searching a document, the user agent should not search text whose
properties prevent it from being visible (such as text that has
visibility="hidden"
), or equivalent text for elements with such
properties (such as "alt
" text for an image that has
visibility="hidden"
).
-
- If the number of matches is known, provide this information to orient the
user.
- It may be confusing to allow users to search for text content that is
not rendered (and thus that they have not viewed). If this type of search
is possible, alert the user of this particular search mode.
- Allow the following additional search functionalities:
- Allow the user to start a search from the beginning of the document rather
than from the current selection or focus.
- Provide distinct alerts for the situation where the user has searched
through all content or where the user has simply reached the end of the
document and needs to wrap to the beginning.
- Allow reverse search so the user doesn't not have to start he search from
the beginning of the document if the search goes too far.
- Allow the user to easily start a search from the beginning of the content
currently rendered in the viewport.
- Provide the option of searching through conditional content that is
associated with rendered content, and render the found conditional content
(e.g., by showing its relation to the rendered content).
-
- For information about when case is significant in a
script, please refer to Section 4.1 of
Unicode [UNICODE].
-
- 9.8 Allow the user to navigate efficiently
to and among important structural elements. Allow forward and backward
sequential navigation to important structural elements. [Priority 2] Content only. (Checkpoint
9.8)
- Note: This specification intentionally
does not identify which "important elements" must be navigable as this will
vary according to markup language. What constitutes "efficient navigation" may
depend on a number of factors as well, including the "shape" of content (e.g.,
serial navigation of long lists is not efficient) and desired granularity
(e.g., among tables, then among the cells of a given table).
-
- User agents should construct the navigation view with the goal of breaking
content into sensible pieces according to the author's design. In most cases,
user agents should not break down content into individual elements for
navigation; element-by-element navigation of the document object does not meet
the goal of facilitating navigation to important pieces of content. (The
navigation view may also be an expanding/contracting outline view; see checkpoint 10.5.) Instead,
user agents are expected to construct the navigation view based on markup.
-
- In HTML 4 [HTML4], important elements include:
A
, ADDRESS
, APPLET
, BUTTON
,
FIELDSET
, DD
, DIV
, DL
,
DT
, FORM
, FRAME
, H1-H6
,
IFRAME
, IMG
, INPUT
, LI
,
LINK
(if rendered), MAP
, OBJECT
,
OL
, OPTGROUP
, OPTION
, P
,
TABLE
, TEXTAREA
, and UL
. HTML also allows
authors to specify keyboard configurations ("accesskey", "tabindex"), which can
serve as hints about what the author considers important.
- Allow navigation based on commonly understood document models, even if they
do not adhere strictly to a Document Type Definition (DTD). For instance, in HTML,
although headings (H1-H6) are not containers, they may be treated as such for
the purpose of navigation. Note that they should be properly nested.
- Use the DOM ([DOM2CORE]) as the basis of
structured navigation (e.g., a postorder traversal). However, for well-known
markup languages such as HTML, structured navigation should take advantage of
the structure of the source tree and what is rendered.
- Follow
operating environment conventions for indicating navigation progress
(e.g., selection
or content
focus).
- Allow the user to limit navigation to the cells of a table (notably left
and right within a row and up and down within a column). Navigation techniques
include keyboard navigation from cell to cell (e.g., using the arrow keys) and
page up/down scrolling. See the section on table navigation.
- Alert the user when navigation has led to the beginning or end of a
structure (e.g., end of a list, end of a form, table row or column end, etc.).
See also checkpoint 1.3.
- For those languages with known (e.g., by specification, schema, metadata,
etc.) conventions for identifying important components, user agents should
construct the navigation tree from those components, allowing users to navigate
up and down the document tree, and forward and backward among siblings. As the
same time, allow users to shrink and expand portions of the document tree. For
instance, if a subtree consists of a long series of links, this will pose
problems for users with serial access to content. At any level in the document
tree (for forward and backward navigation of siblings), limit the number of
siblings to between five and ten. Break longer lists down into structured
pieces so that users can access content efficiently, decide whether they want
to explore it in detail, or skip it and move on.
- Tables and forms illustrate the utility of a recursive navigation
mechanism. The user should be able to navigate to tables, then change "scope"
and navigate within the cells of that table. Nested tables (a table within the
cell of another table) fit nicely within this scheme. However, the headers of a
nested table may provide important context for the cells of the same row(s) or
column(s) containing the nested table. The same ideas apply to forms: users
should be able to navigate to a form, then among the controls within that
form.
- Navigation and orientation go together. The user agent should allow the
user to navigate to a location in content, explore the context, navigate again,
etc. In particular, user agents should allow users to:
- Navigate to a piece of content that the author has identified as important
according to the markup language specification and conventional usage. In HTML,
for example, this includes headings, forms, tables, navigation mechanisms, and
lists.
- Navigate past that piece of content (i.e., avoid the details of that
component).
- Navigate into that piece of content (i.e., chose to view the details of
that component).
- Change the navigation view as they go, expanding and contracting portions
of content that they wish to examine or ignore. This will speed up navigation
and facilitate orientation at the same time.
- Provide context-sensitive navigation. For instance, when the user navigates
to a list or table, provide locally useful navigation mechanisms (e.g., within
a table, cell-by-cell navigation) using similar input commands.
- Allow users to skip author-specified navigation mechanisms such as
navigation bars. For instance, navigation bars at the top of each page at a Web
site may force users with screen readers or some physical disabilities to wade
through many links before reaching the important information on the page. User
agents may facilitate browsing for these users by allowing them to skip
recognized navigation bars (e.g., through a configuration option).
Some techniques for this include:
- Providing a functionality to jump to the first non-link content.
- If the number of elements of a particular type is known, provide this
information to orient the user.
- In HTML, the MAP element may be used to mark up a navigation bar (even when
there is no associated image). Thus, users might ask that MAP elements not be
rendered in order to hide links inside the MAP element. User agents might allow
users to hide MAP elements selectively. For example, hide any MAP element with
a "
title
" attribute specified. Note: Starting in
HTML 4, the MAP element allows block content, not just AREA
elements.
- Allow depth-first as well as breadth-first navigation.
- Allow users to navigate synchronized multimedia presentations. See also checkpoint
4.5.
-
- Allow the user to navigate characters, words, sentences, paragraphs,
screenfuls, etc. according to conventions of the natural
language. This benefits users of speech-based user agents and has
been implemented by several screen readers, including Winvision
[WINVISION], Window-Eyes
[WINDOWEYES], and JAWS for Windows
[JFW].
-
- The following is a summary of ideas provided by the National Information
Standards Organization with respect to Digital Talking Books
[TALKINGBOOKS]:
A talking book's "Navigation Control Center" (NCC) resembles a traditional
table of contents, but it is more. It contains links to all headings at all
levels in the book, links to all pages, and links to any items that the reader
has chosen not to have read. For example, the reader may have turned off the
automatic reading of footnotes. To allow the user to retrieve that information
efficiently, the reference to the footnote is placed in the NCC and the reader
can go to the reference, understand the context for the footnote, and then read
the footnote.
Once the reader is at a desired location and wishes to begin reading, the
navigation process changes. Of course, the reader may elect to read
sequentially, but often some navigation is required (e.g., frequently people
navigate forward or backward one word or character at a time). Moving from one
sentence or paragraph at a time is also needed. This type of local navigation
is different from the global navigation used to get to the location of what you
want to read. It is frequently desirable to move from one block element to the
next. For example, moving from a paragraph to the next block element which may
be a list, blockquote, or sidebar is the normally expected mechanism for local
navigation.
-
- 9.9
Allow
configuration and control of
the set of important elements required by checkpoint 9.8 and checkpoint 10.5. Allow the user to include and exclude
element types in the set of elements.
[Priority 3] Content only. (
Checkpoint 9.9)
- Note: For example, allow the user to navigate only
paragraphs, or only headings and paragraphs, etc. See also checkpoint 6.4.
-
- Allow the user to navigate HTML elements that share the
same "class" attribute.
- The CSS
'display' and
'visibility' properties ([CSS2], sections 9.2.5 and 11.2,
respectively), allow the user to override the default settings in user style
sheets.
Example.
The following CSS 2 style sheet will turn the display off of all
HTML elements inside the BODY element except heading elements:
<STYLE type="text/css">
BODY * { display: none }
H1, H2, H3, H4, H5, H6 { display: block }
</STYLE>
Another approach would be to use class selectors to identify those elements
to hide or display.
End example.
-
- Allow the user to navigate according to similar styles (which may be an
approximation for similar element types).
-
Checkpoints
- 10.1 Make available to the user the
purpose of each table and the relationships among the table cells and headers.
[Priority 1] Content only. (Checkpoint
10.1)
- Note: This checkpoint refers only to table information
that the user can
recognize. Depending on the table, some techniques may be more efficient
than others for conveying data relationships. For many tables, user agents
rendering in two dimensions may satisfy this checkpoint by rendering a table as
a grid and by ensuring that users can find headers associated with cells.
However, for large tables or small viewports, allowing the user to query cells
for information about related headers may improve access. This checkpoint is an
important special case of
checkpoint 2.1.
-
- The more complex the table, the more clues to table structure are needed.
Make available information summarizing table structure, including any table
head and foot rows, and possible row grouping into multiple table bodies,
column groups, header cells and how they relate to data cells, the grouping and
spanning of rows and columns that apply to qualify any cell value, cell
position information, table dimensions, etc.
-
- Refer to the
THEAD, TBODY, and TFOOT elements of HTML 4 ([HTML4], section 11.2.3). These
elements may be "fixed" to the screen (or repeated on paper) with the 'fixed'
value of the
CSS2 'position' property ([CSS2], section 9.3.1). When these
elements are used by authors, users can scroll through data while retaining
headers and footers "in view".
- In HTML, beyond the TR, TH, and TD elements, the table attributes
"summary", "abbr", "headers", "scope", and "axis" provide information about
relationships among cells and headers. For more information, see the section on
table techniques.
- When rendering a table serially, allow the user to specify how cell header
information should be rendered before cell data information. Some possibilities
are illustrated by the
CSS2 'speak-header' property ([CSS2], section 17.7.1).
-
-
-
10.2 Provide a mechanism for
highlighting the
selection and
content focus. Allow the user to configure the highlight styles. The
highlight mechanism must not rely on color alone. For graphical viewports, if
the highlight mechanism involves colors or text
decorations, allow the user to choose from among the full range of
colors or text decorations supported by the
operating environment.
[Priority 1] Content only. (
Checkpoint 10.2)
- Note: Examples of highlight mechanisms include foreground
and background color variations, underlining, distinctive voice pitches,
rectangular boxes, etc. Because the selection and focus change frequently, user
agents should not highlight them using mechanisms (e.g., font size variations)
that cause content to reflow as this may disorient the user. See also checkpoint
7.1.
-
- Two reasons not why it is important not to rely on color alone as a
distinguishing factor are that some users may not perceive colors and some
devices may not render them.
-
- Inherit selection
and focus
information from user's settings for the
operating environment.
- A highlighted selection or focus may span text with different background
colors, text foreground colors, font families, etc.
- For selection:
- For focus, implement the
':hover', ':active', and ':focus' pseudo-classes of CSS 2 ([CSS2], section 5.11.3). and dynamic outlines
and focus of CSS 2 ([CSS2], sections 5.11.3 and 18.4.1,
respectively).
Example.
The following rule will cause links with focus to appear with a blue
background and yellow text.
A:focus { background: blue; color: yellow }
The following rule will cause TEXTAREA
elements with focus to
appear with a particular focus outline:
TEXTAREA:focus { outline: thick black solid }
-
- Test the user agent to ensure that individuals who have low vision and use
screen magnification software are able to follow highlighted item(s).
-
- 10.3 Ensure that all of the default highlight
styles for the
selection, content
focus, enabled
elements, recently visited links, and fee links
(1) do not rely on color alone, and (2) differ from each other, and not by
color alone. [Priority 1] Content only. (Checkpoint
10.3)
- Note: For instance, by default a
graphical user agent may present the selection using color and a dotted
outline, the focus using a solid outline, enabled elements as underlined in
blue, recently visited links as dotted underlined in purple, and fee links
using a special icon or flag to draw the user's attention.
-
- If the user overrides the default styling for any one of these mechanisms,
the new styling may interfere with the others. Therefore, the user agent should
allow the user to configure them all at once or should alert the user to
potential conflicts when change are made. For instance, if the user configures
both the selection and focus highlighting to use colors, there may be a
conflict (especially if the colors are the same or similar).
-
- 10.4 Provide a mechanism for
highlighting all enabled elements, recently visited links, and
fee links.
Allow the user to configure the highlight styles. The highlight mechanism must
not rely on color alone. For graphical viewports, if the highlight mechanism
involves colors, fonts, or text decorations, allow the user to choose from
among the full range of colors, fonts, or text decorations supported by the
operating environment. For an image map, the user agent must
highlight the image map as a whole and should allow configuration to highlight
each enabled region. [Priority 2] Content
only. (Checkpoint
10.4)
- Note: Examples of highlight mechanisms include foreground
and background color variations, font variations, underlining, distinctive
voice pitches, rectangular boxes, etc.
-
- For example, most graphical user agents highlight all the links on a page
so that users know at a glance where to interact.
-
- Do not rely solely on fonts or colors to alert the user whether or not the
link has previously been followed. Allow the user to configure how information
will be presented (colors, sounds, status bar messages, some combination,
etc.).
- Use CSS2 [CSS2] to add style to these
different classes of elements. In particular, consider the
'text-decoration' property ([CSS2], section 16.3.1), aural
cascading style sheets, font properties, and color properties.
- For enabled elements, implement CSS2
attribute selectors to match elements with associated scripts ([CSS2], section 5.8).
- For fee links:
- The W3C specification "Common Markup for micropayment per-fee-links"
[MICROPAYMENT] describes how
authors may mark up micropayment information in an interoperable manner.
- Use standard, accessible interface controls to present information about
fees and to prompt the user to confirm payment.
- For a link that has
content focus, allow the user to query the link for fee information
(e.g., by activating a menu or key stroke).
-
-
- Test the user agent to ensure that individuals who have low vision and use
screen magnification software are able to follow highlighted item(s).
-
- For links, see the section on link
techniques, the visited links example in the section on generated content techniques, and
techniques for checkpoint
9.2.
-
- 10.5
Make available to the user an "outline" view of
content, composed of labels for important
structural elements (e.g., heading text, table titles, form titles, etc.).
[Priority 2] Content only. (
Checkpoint 10.5)
- Note: This checkpoint is meant to
provide the user with a simplified view of content (e.g, a table of contents).
What constitutes a label is defined by each markup language specification. For
example, in HTML, a heading (
H1
-H6
) is a label for
the section that follows it, a CAPTION
is a label for a table, the
"title
" attribute is a label for its element, etc. A label is not
required to be text only. For
important elements that do not have associated labels, user agents may generate
labels for the outline view. For information about what constitutes the set of
important structural elements, please see the Note following checkpoint 9.8. By making the
outline view navigable, it is possible to satisfy this checkpoint and checkpoint 9.8 together: Allow
users to navigate among the important elements of the outline view, and to
navigate from a position in the outline view to the corresponding position in a
full view of content. See
also checkpoint 9.9.
-
- For instance, in HTML, labels include the following:
- The
CAPTION
element is a label for TABLE
- The "
title
" attribute is a label for many elements.
- The
H1
-H6
elements are labels for sections that
follow
- The
LABEL
element is a label for form control
- The
LEGEND
element is a label for a set of form controls
- The
TH
element is a label for a row/column of table
cells.
- The
TITLE
element is a label for the document.
- Allow the user to expand or shrink portions of the outline view (configure
detail level) for faster access to important parts of content.
- Hide portions of content by using the CSS
'display' and
'visibility' properties ([CSS2], sections 9.2.5 and 11.2,
respectively).
- Provide a structured view of form
controls (e.g., those grouped by
LEGEND
or
OPTGROUP
in HTML) along with their labels.
-
-
- For documents that do not use structure properly, user agents may attempt
to create an outline based on the rendering of elements and heuristics about
what elements may indicate about document structure.
-
- See structured navigation techniques for checkpoint 9.8.
-
- 10.6 To help the user decide whether to
traverse a link, make available the following information about it: link
element content, link title, whether the link is internal to the resource
(e.g., the link is to a target in the same Web page), whether the user has
traversed the link recently, whether traversing it may involve a fee, and
information about the type, size, and natural language of linked Web resources.
The user agent is not required to compute or make available information that
requires retrieval of linked
Web resources. [Priority 3]
Content only. (Checkpoint
10.6)
-
- Some markup languages allow authors to provide hints about the nature of
linked content (e.g., in HTML 4 [HTML4], the "hreflang" and "type"
attributes on the A element). Specifications should indicate when this type of
information is a hint from the author and when these hints may be overridden by
another mechanism (e.g., by HTTP headers in the case of HTML). User agent
developers should make the author's hints available to the user (prior to
retrieving a resource), but should provide definitive information once
available.
- Links may be simple (e.g., HTML links) or more complex, such as those
defined by the XML Linking Language (XLink)
[XLINK].
- The scope of "recently followed link" depends on the user agent. The user
agent may allow the user to configure this parameter, and should allow the user
to reset all links as "not followed recently".
- User agents should cache information determined as the result of retrieving
a Web resource and should make it available to the user. Refer to HTTP/1.1
caching mechanisms described in RFC 2616
[RFC2616], section 13.
- For a link that has
content focus, allow the user to query the link for information
(e.g., by activating a menu or key stroke).
- Do not mark all local links (to anchors in the same page) as visited when
the page has been visited.
-
- User agents may provide information about any input bindings associated
with a link. See
checkpoint 11.2.
-
- See the section on link
techniques.
-
- User agents may use HTTP HEAD rather than GET for information about size,
language, etc. Refer to RFC 2616 [RFC2616], section 9.3
- For information about content size in HTTP/1.1, refer to RFC 2616
[RFC2616], section 14.13. User agents are not expected to compute
content size recursively (i.e., by adding the sizes of resources referenced by
URIs within another resource).
- For information about content language in HTTP/1.1, refer to RFC 2616
[RFC2616], section 14.12.
- For information about content type in HTTP/1.1, refer to RFC 2616
[RFC2616], section 14.17.
-
Checkpoints for the user interface
- 10.7 Provide a mechanism for
highlighting the viewport with the current
focus. For graphical viewports, the default highlight mechanism must
not rely on color alone. [Priority 1] User
agent only. (Checkpoint
10.7)
- Note: This includes highlighting and
identifying frames. This checkpoint is an important special case of checkpoint 1.1. See also
to checkpoint checkpoint
7.3.
-
- Provide a setting that causes a window that is the viewport with the
current focus to be maximized automatically. For example, maximize the parent
window of the browser when launched, and maximize each child window
automatically when it receives focus.
Maximizing does not necessarily mean occupying the whole screen or parent
window; it means expanding the viewport so that users have to scroll
horizontally or vertically as little as possible.
- If the viewport with the current focus is a frame or the user does not want
windows to pop to the foreground, use colors, reverse videos, or other
graphical clues to indicate the viewport with the current focus.
- For speech or braille output, use the frame or window title to identify the
viewport with the current focus.
- Use
operating environment conventions, for specifying selection and
content focus (e.g., schemes in Windows).
- Implement the
':hover', ':active', and ':focus' pseudo-classes of CSS 2 ([CSS2], section 5.11.3). This allows
users to modify content focus rendering with user style
sheets.
-
-
- See the section on frame
techniques.
-
-
10.8 Ensure that when a viewport's selection
or content
focus changes, it is in the
viewport after the change.
[Priority 2] User agent only. (
Checkpoint 10.8)
- 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.
-
- There are times when the content focus changes (e.g., link navigation) and
the viewport should move to track it. There are other times when the viewport
changes position (e.g., scrolling) and the content focus is moved to follow it.
In both cases, the focus (or selection) is in the viewport after the
change.
- If a search causes the selection or focus to change, ensure that the found
content is not hidden by the search prompt.
- When the content focus changes, register the newly focused element in the
navigation sequence; sequential navigation should start from there.
- Unless viewports have been coordinated explicitly, changes to selection or
focus in one viewport should not affect the selection or focus in another
viewport.
- The persistence of the selection or focus in the viewport will vary
according to the type of viewport. For any viewport with persistent rendering
(e.g., a two-dimensional graphical or tactile viewport), the focus or selection
should remain in the viewport after the change until the user changes the
viewport. For any viewport without persistent rendering (e.g., and audio
viewport), once the focus or selection has been rendered, it will no longer be
"in" the viewport. In a pure audio environment, the whole persistent context is
in the mind of the user. In a graphical viewport, there is a large shared
buffer of dialog information in the display. In audio, there is no such
sensible patch of interaction that is maintained by the computer and accessed,
ad lib, by the user. The audio rendering of content requires the elapse of
time, which is a scarce resource. Consequently, the flow of content through the
viewport has to be managed more carefully, notably when the content was
designed primarily for graphical rendering.
- If the rendered selection or focus does not fit entirely within the limits
of a graphical viewport:
- if the region actually displayed prior to the change was within the
selection or focus, do not move the viewport.
- otherwise, if the region actually displayed prior to the change was not
within the newly selected or focused content, move to display at least the
initial fragment of such content.
-
- 10.9 Indicate the relative position of
the viewport
in rendered
content (e.g., the proportion of an audio or video clip that has
been played, the proportion of a Web page that has been viewed, etc.). [Priority 3] User agent only. (Checkpoint
10.9)
- Note: The user agent may calculate the
relative position according to content focus position, selection position, or
viewport position, depending on how the user has been browsing. The user agent
may indicate the proportion of content viewed in a number of ways, including as
a percentage, as a relative size in bytes, etc. For two-dimensional renderings,
relative position includes both vertical and horizontal positions.
-
- Provide a scrollbar for the viewport. Some specifications address scrolling
requirements or suggestions explicitly, such as for
the
THEAD
and TBODY
elements of HTML 4 ([HTML4], section 11.2.3) and the
'overflow' property of CSS 2 ([CSS2], section 11.1.1).
- Indicate the size of the document, so that users may decide whether to
download for offline viewing. For example, the playing time of an audio file
could be stated in terms of hours, minutes, and seconds. The size of a
primarily text-based Web page might be stated in both kilobytes and screens,
where a screen of information is calculated based on the current dimensions of
the viewport.
- Indicate the number of screens of information, based on the current
dimensions of the viewport (e.g., "screen 4 of 10").
- Use a variable pitch audio signal to indicate the viewport's different
positions.
- Provide standard markers for specific percentages through the
document.
- Provide markers for positions relative to some position – a user
selected point, the bottom, the
H1
, etc.
- Put a marker on the scrollbar, or a highlight at the bottom of the page
while scrolling (so you can see what was the bottom before you started
scrolling).
- For images that render gradually (coarsely to finely), it is not necessary
to show percentages for each rendering pass.
-
- Allow users to configure what status information they want rendered. Useful
status information includes:
- Document proportions (numbers of lines, pages, width, etc.);
- Number of elements of a particular type (e.g., tables, forms, and
headings);
- Whether the viewport is at the beginning or end of the document;
- Size of document in bytes;
- The number of controls in a form and controls in a form control group
(e.g.,
FIELDSET
in HTML).
-
Checkpoints
-
11.1 Provide information to the user about current user preferences
for input
configurations. [Priority 1]
User agent only. (
Checkpoint 11.1)
- Note: To satisfy this checkpoint, the
user agent may make available binding information in a centralized fashion
(e.g., a list of bindings) or a distributed fashion (e.g., by listing keyboard
shortcuts in user interface menus).
-
- See input configuration
techniques.
-
-
11.2 Provide a centralized view of the current author-specified input
configuration bindings.
[Priority 2] Content only. (
Checkpoint 11.2)
- Note: For example, for HTML documents,
provide a view of keyboard bindings specified by the author through the
"
accesskey
" attribute. The intent of this checkpoint is to
centralize information about author-specified bindings so that the user does
not have to read the entire content first to find out what bindings are
available. The user agent may satisfy this checkpoint by providing different
views for different input modalities (keyboard, pointing device, voice,
etc.).
-
- If the user agent offers a special view that lists author-specified
bindings, allow the user to navigate easily back and forth between the viewport
with the current focus and the list of bindings.
-
- In addition to providing a centralized view of bindings, allow users to
find out about bindings in content. For example, highlight enabled elements
that have associated event handlers (e.g., by indicating bindings near the
element).
-
- See input configuration
techniques.
-
- 11.3 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 standard bindings for the
operating environment (e.g., for access to help). [Priority 2] User agent only. (Checkpoint
11.3)
- Note: 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). See also checkpoint 11.5, checkpoint 11.7, and checkpoint 12.3.
-
- Many people benefit from direct access to important user agent
functionalities (e.g., via a single key stroke or short voice command): users
with poor physical control (who might mistakenly repeat a key stroke), users
who fatigue easily (for whom key combinations involve significant effort),
users who cannot remember key combinations, and any user who wants to operate
the user agent efficiently.
-
- Allow users to choose from among pre-packaged configurations, to override
some of the chosen configuration, and to save it as a
profile. Not only will the user save time
configuring the user agent, but this will reduce questions to technical support
personnel.
- Allow users to restore easily the default input configuration.
- Allow users to create macros and bind them to key strokes or other input
methods.
- Test the default keyboard configuration for usability. Ask users with
different disabilities and combinations of disabilities to test
configurations.
-
- See input configuration
techniques.
-
- 11.4 Allow the user to override any binding
in the 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 (i.e., one key press performs the task, with zero modifier
keys). If the number of physical keys on the keyboard is less than the number
of functionalities required by checkpoint 11.5, allow single-key bindings for as many of
those functionalities as possible. The user agent is not required to allow the
user to override standard bindings for the
operating environment (e.g., for access to help). [Priority 2] User agent only. (Checkpoint
11.4)
- Note: In this checkpoint, "key" refers
to a physical key of the keyboard (rather than, say, a character of the
document character set). 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. This checkpoint does not require single physical key bindings for
character input, only for the activation of user agent functionalities. For
information about access to user agent functionality through a keyboard API,
see checkpoint 6.7.
-
- When using a physical keyboard, some users require single-key access,
others require that keys activated in combination be physically close together,
while others require that they be spaced physically far apart.
- In some modes of interaction (e.g., when the user is entering text), the
number of available single keys will be significantly reduced.
-
- Offer a single-key mode where, once the user has entered into that mode
(e.g., by pressing a single key), most of the keys of the keyboard are
configurable for single-key operation of the user agent. Allow the user to exit
that mode by pressing a single key as well. For example, Opera
[OPERA] includes a mode in which users can access important user
agent functionalities with single strokes from the numeric keypad.
- Consider distance between keys and key alignment (e.g., "9/I/K", which
align almost vertically on many keyboards) in the default configuration. For
instance, if Enter is used to activate links, put other link
navigation commands near it (e.g., page up/down, arrow keys, etc. on many
keyboards). In configurations for users with reduced mobility, pair related
functionalities on the keyboard (e.g., left and right arrows for forward and
back navigation).
- Mouse Keys (available in some
operating environments) allow users to simulate the mouse through
the keyboard. They provide a usable command structure without interfering with
the user interface for users who do not require keyboard-only and single-key
access.
-
- Allow users to accomplish tasks through repeated key strokes (e.g.,
sequential navigation) since this means less physical repositioning for all
users. However, repeated key strokes may not be efficient for some tasks. For
instance, do not require the user to position the pointing device by pressing
the "down arrow" key repeatedly.
- So that users do not mistakenly activate certain functionalities, make
certain combinations "more difficult" to invoke (e.g., users are not likely to
press Control-Alt-Delete accidentally).
-
- 11.5
Ensure that the default input configuration includes bindings for the
following functionalities required by other checkpoints in this document: move
focus to next enabled
element; move focus to previous enabled element; activate focused
link; search for text; search again for same text; increase size of rendered
text; decrease size of rendered text; increase global volume; decrease global
volume; (each of) stop, pause, resume, fast advance, and fast reverse selected
audio and
animations (including video and animated images). If the user agent
supports
the following functionalities, the default input configuration must also
include bindings for them: next history state (forward); previous history state
(back); enter URI for new resource; add to favorites (i.e., bookmarked
resources); view favorites; stop loading resource; reload resource; refresh
rendering; forward one viewport; back one viewport; next line; previous line.
[Priority 2] User agent only. (
Checkpoint 11.5)
- Note: This checkpoint does not make any
requirements about the ease of use of default input configurations, though
clearly the default configuration should include single-key bindings and allow
easy operation. Ease of use is ensured by the configuration requirements of checkpoint 11.3.
-
- Input configurations should allow quick and direct navigation that does not
rely on graphical
output. Do not require the user to navigate through a graphical user interface
as the only way to activate a functionality.
-
- Provide different input configuration
profiles (e.g., one keyboard profile with key combinations close
together and another with key combinations far apart).
- Offer a mode that makes the input configuration compatible with other
versions of the software (or with other software).
- Provide convenient bindings for controlling the user interface, such as
showing, hiding, moving, and resizing graphical
viewports.
- Allow the user to configure how much the viewport should move when
scrolling the viewport backward or forward through content (e.g., for a
graphical viewport, "page down" causes the viewport to move half the height of
the viewport, or the full height, or twice the height, etc.).
-
- See also checkpoint
7.4.
-
- 11.6 For the configuration requirements of
this document, allow the user to save user preferences in at least one
user profile. Allow users to choose from
among available profiles or no profile (i.e., the user agent default settings).
[Priority 2] User agent only. (Checkpoint
11.6)
- Note: The configuration requirements of
the checkpoints in this document involve user preferences for styles,
presentation rates, input configurations, navigation, viewport
behavior, and user agent prompts and alerts.
-
- Follow applicable operating environment conventions for input
configuration
profiles.
- Allow users to choose a different profile, to switch rapidly between
profiles, and to return to the default input configuration.
-
- 11.7 For graphical user interfaces,
allow the user to configure
the position of controls on tool bars of the user agent user interface, to add or remove
controls for the user interface from a predefined set, and to restore the
default user interface. [Priority 3] User
agent only. (Checkpoint
11.7)
- Note: This checkpoint is a special case of checkpoint 11.3.
-
- Use standard operating environment controls for allowing
configuration of font sizes, speech rates, and other style parameters.
- Allow the user to show and hide controls. This benefits users with
cognitive disabilities and users who navigate user interface controls
sequentially.
- Allow the user to choose icons and/or text.
- Allow the user to change the grouping of icons and the order of menu
entries (e.g., for faster access to frequently used controls).
- Allow multiple icon sizes (big, small, other sizes). Ensure that these
values are applied consistently across the user interface.
- Allow the user to change the position of control bars, icons, etc. Do not
rely solely on drag-and-drop for reordering tool bar. Allow the user to
configure the user
agent user interface in a device-independent manner (e.g., through a
text-based
profile).
-
Checkpoints
- 12.1 Ensure that at least one version of
the product
documentation conforms to at least Level Double-A of the Web Content
Accessibility Guidelines 1.0
[WCAG10]. [Priority 1] User
agent only. (Checkpoint
12.1)
-
- User agents may provide documentation in many formats, but at least one
must conform to at least Level Double-A of the Web Content Accessibility
Guidelines 1.0 [WCAG10].
- Remember to keep documentation accessible as the product evolves (e.g.,
when bug fixes are published, etc.).
-
- Distribute accessible documentation over the Web, on CD-ROM, or by
telephone. Alternative hardcopy formats may also benefit some users.
- For example, for conformance to the Web Content Accessibility Guidelines
1.0 [WCAG10]:
- Provide text
equivalents of all non-text content (e.g., graphics,
audio-only presentations, etc.);
- Provide extended descriptions of screen-shots, flow charts, etc.;
- Provide a text
equivalent for audio user agent tutorials. Tutorials that use speech
to guide a user through the operation of the user agent should also be
available at the same time as
graphical representations.
- Use clear and consistent navigation and search mechanisms;
- Use the
NOFRAMES
element when the support/documentation is
presented in a FRAMESET
;
- See also checkpoint
12.3.
- Describe the user interface with device-independent terms. For example, use
"select" instead of "click on".
- Provide documentation in small chunks (for rapid downloads) and also as a
single source (for easy download and/or printing). A single source might be a
single HTML file or a compressed archive of several
HTML documents and included images.
- Ensure that run-time help and any Web-based help or support information is
accessible and may be operated with a single, well-documented, input command
(e.g., key stroke). Use operating environment conventions for input
configurations related to run-time help.
- Ensure that product identification codes are accessible to users so they
may install their software. Codes printed on product cases may not be
accessible to people with visual disabilities.
-
- Provide accessible documentation for all audiences: end users, developers,
etc. For instance, developers with disabilities may wish to add accessibility
features to the user agent, and so require information on available APIs and other implementation details.
- Provide documentation in alternative formats such as braille (refer to
"Braille Formats: Principles of Print to Braille Transcription 1997" [BRAILLEFORMATS]), large
print, or audio tape. Agencies such as Recording for the Blind and Dyslexic
[RFBD] and the National Braille Press [NBP]
can create alternative formats.
-
-
12.2
Document all user agent features that benefit accessibility. [Priority 1] User agent only. (
Checkpoint 12.2)
- Note: For example, review the
documentation or help system to ensure that it includes information about the
functions and capabilities of the user agent that are required by WAI Accessibility Guidelines,
platform-specific accessibility guidelines, etc. The documentation of
accessibility features should be integrated into the documentation as a
whole.
-
- Document any features that affect accessibility and that depart from system
conventions.
- Provide a sensible index to accessibility features. For instance, users
should be able to find "How to turn off blinking text" in the documentation
(and the user interface). The user agent may support this feature by turning
off scripts, but users should not have to guess (or know) that turning off
scripts will turn off blinking text.
- Document configurable features in addition to defaults for those
features.
- Document the features implemented to conform with these guidelines.
- Include references to accessibility features in both the table of contents
and index of the documentation.
- In developer documentation, document the APIs that are required by this
document. Please see the requirements of checkpoint 6.6, checkpoint 6.1, checkpoint 6.3, and checkpoint 6.4.
-
-
12.3
Document the default input configuration (e.g., the default keyboard
bindings). [Priority 1] User agent only.
(
Checkpoint 12.3)
- Note: If the default input
configuration is inconsistent with conventions of the operating environment,
the documentation should alert the user.
-
- As an example of online documentation of keyboard support, refer to the Mozilla
Keyboard Planning FAQ and Cross Reference for the Mozilla browser
[MOZILLA].
-
-
12.4 In a dedicated section of the
documentation, describe all features of the user agent that benefit
accessibility. [Priority 2] User agent
only. (
Checkpoint 12.4)
- Note: This is a more specific
requirement than
checkpoint 12.2.
-
- Integrate information about accessibility features throughout the
documentation. The dedicated section on accessibility should provide access to
the documentation as a whole rather than standing alone as an independent
section. For instance, in a hypertext-based help system, the section on
accessibility may link to pertinent topics elsewhere in the documentation.
- Ensure that the section on accessibility features is easy to find.
-
- 12.5 In each software release,
document all changes that affect accessibility. [Priority 2] User agent only. (Checkpoint
12.5)
- Note: Features that affect accessibility are those
required by WAI
Accessibility Guidelines, platform-specific accessibility guidelines, etc.
-
- In particular, document changes to the user interface.
-
- Either describe the changes that affect accessibility in the section of the
documentation dedicated to accessibility features (see checkpoint 12.4) or link
to the changes from the dedicated section.
- Provide a text description of changes (e.g., in a README file).
-