- From: gregory j. rosmaita <oedipus@hicom.net>
- Date: Thu, 26 Jul 2001 22:04:57 -0400
- To: <w3c-wai-gl@w3.org>
KB: Most modern browsers can or should include this in configuration
options
GJR: which means that the answer is (all together now) the "until user
agents..." clause still applies until there are actually user agents that
conform to the following UAAG checkpoints (the text of which is drawn from
the 14 july 2001 working group working draft of UAAG 1.0 [reference 1]:
<quote>
2.3 Render conditional content. (P1)
1. Allow configuration to provide access to each piece of unrendered
conditional content "C".
2. The configuration may be a switch that, for all content, turns on
or off the access mechanisms described in the next provision.
3. When a specification does not explain how to provide access to
this content, do so as follows:
+ If C is a summary, title, alternative, description, or
expansion of another piece of content D, provide access
through at least one of the following mechanisms:
o (1a) render C in place of D;
o (2a) render C in addition to D;
o (3a) provide access to C by querying D. In this case,
the user agent must also alert the user, on a
per-element basis, to the existence of C (so that the
user knows to query D);
o (4a) allow the user to follow a link to C from the
context of D.
+ Otherwise, provide access to C through at least one of the
following mechanisms:
o (1b) render a placeholder for C, and allow the user to
view the original author-supplied content associated
with each placeholder;
o (2b) provide access to C by query (e.g., allow the user
to query an element for its attributes). In this case,
the user agent must also alert the user, on a
per-element basis, to the existence of C;
o (3b) allow the user to follow a link in context to C.
4. To satisfy this checkpoint, the user agent may provide access on a
per-element basis (e.g., by allowing the user to query individual
elements) or for all elements (e.g., by offering a configuration
to render conditional content all the time).
For all content
Note: For instance, an HTML user agent might allow users to query each
element for access to conditional content supplied for the "alt",
"title", and "longdesc" attributes. Or, the user agent might allow
configuration so that the value of the "alt" attribute is rendered in
place of all IMG elements (while other conditional content might be
made available through another mechanism). See checkpoint 2.10 for
additional placeholder requirements.
2.4 Allow time-independent interaction. (P1) [note: the wording of
this checkpoint will change in the next draft - consult the minute's
of the 26 july 2001 UA WG telecon, archived at:
<http://lists.w3.org/Archives/Public/w3c-wai-ua/2001JulSep/0155>
for more details of the discussion of this checkpoint -- GJR]
1. 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.
2. In this configuration, alert the user when the session has been
paused and which enabled elements are time-sensitive.
3. When the user pauses a real-time presentation, the user agent may
discard packets that continue to arrive during the pause.
For all rendered content
Note: In this configuration, the user agent may have to pause the
presentation more than once if there is more than one opportunity for
time-sensitive input. When pausing, pause synchronized content as well
(whether rendered in the same or different viewports) per checkpoint
2.6. In SMIL 1.0 [SMIL], for example, the "begin", "end", and "dur"
attributes synchronize presentation components. The user may
explicitly complete input in many different ways (e.g., by following a
link that replaces the current time-sensitive resource with a
different resource). This checkpoint does not apply when the user
agent cannot recognize the time interval in the presentation format,
or when the user agent cannot control the timing (e.g., because it is
controlled by the server). See also checkpoint 3.5, which involves
client-driven content refresh.
2.7 Repair missing content. (P2)
1. Allow configuration to generate repair text when the user agent
recognizes that the author has failed to provide conditional
content that was required by the format specification.
2. The user agent may satisfy this checkpoint by basing the repair
text on any of the following available sources of information: URI
reference, content type, or element type.
For all content
Note: Some markup languages (such as HTML 4 [HTML4] and SMIL 1.0
[SMIL] require the author to provide conditional content for some
elements (e.g., the "alt" attribute on the IMG element). Repair text
based on URI reference, content type, or element type is sufficient to
satisfy the checkpoint, but may not result in the most effective
repair. Information that may be recognized as relevant to repair might
not be "near" the missing conditional content in the document object.
For instance, instead of generating repair text on a simple URI
reference, the user agent might look for helpful information near a
different instance of the URI reference in the same document object,
or might retrieve useful information (e.g., a title) from the resource
designed by the URI reference.
2.9 Render conditional content automatically. (P3)
1. Allow configuration to render all conditional content
automatically. The user agent is not required to render all
conditional content at the same time in a single viewport.
2. Provide access to this content according to format specifications
or where unspecified, by applying one of the following techniques
described in checkpoint 2.3: 1a, 2a, or 1b.
For all content
Note: For instance, an HTML user agent might allow configuration so
that the value of the "alt" attribute is rendered in place of all IMG
elements (while other conditional content might be made available
through another mechanism). The user agent may offer multiple
configurations (e.g., a first configuration to render one type of
conditional content automatically, a second to render another type,
etc.).
2.10 Toggle placeholders. (P3)
1. Once the user has viewed the original author-supplied content
associated with a placeholder, allow the user to turn off the
rendering of the author-supplied content.
For all rendered content
Note: For example, if the user agent substitutes the author-supplied
content for the placeholder in context, allow the user to "toggle"
between placeholder and the associated content. Or, if the user agent
renders the author-supplied content in a separate viewport, allow the
user to close that viewport. Note: See checkpoint 2.3, provision (1b)
for placeholder requirements.
3.1 Toggle background images. (P1)
1. Allow configuration not to render background images.
2. In this configuration, the user agent is not required to retrieve
background images from the Web.
3. This checkpoint only requires control of background images for
"two-layered renderings", i.e., one rendered background image with
all other content rendered "above it".
For all content
Content type labels: Image.
Note: See checkpoint 2.3 for information about how to provide access
to unrendered background images. When background images are not
rendered, user agents should render a solid background color instead
(see checkpoint 4.3).
3.2 Toggle audio, video, animated images. (P1)
1. Allow configuration not to render audio, video, or animated images
except on explicit user request. This configuration is required
for content rendered without any user interaction (including
content rendered on load or as the result of a script), as well as
content rendered as the result of user interaction (e.g., when the
user activates a link).
2. The user agent may satisfy this checkpoint by making video and
animated images invisible and audio silent, but this technique is
not recommended.
3. When configured not to render content except on explicit user
request, the user agent is not required to retrieve the audio,
video, or animated image from the Web until requested by the user.
For all content
Content type labels: Animation, Video, Audio.
Note: See checkpoint 2.3 for information about how to provide access
to unrendered audio, video, and animated images. See also checkpoint
4.5, checkpoint 4.9, and checkpoint 4.10.
3.3 Toggle animated/blinking text. (P1)
1. Allow configuration to render animated or blinking text as
motionless, unblinking text. Blinking text is text whose visual
rendering alternates between visible and invisible, any rate of
change.
2. In this configuration, the user must still have access to the same
text content, but the user agent may render it in a separate
viewport (e.g., for large amounts of streaming text).
3. The user agent also satisfies this checkpoint by always rendering
animated or blinking text as motionless, unblinking text.
For all content
Content type labels: VisualText.
Note: Animation (a rendering effect) is different from streaming (a
delivery mechanism). Streaming content might be rendered as an
animation (e.g., an animated stock ticker) or as static text (e.g.,
movie subtitles, which are rendered for a limited time, but do not
give the impression of movement). See also checkpoint 3.5. apply for
blinking and animation effects that are caused by mechanisms that the
user agent cannot recognize.
4.4 Slow multimedia. (P1)
1. Allow the user to slow the presentation rate of audio and
animations (including video and animated images).
2. For a visual track, provide at least one setting between 40% and
60% of the original speed.
3. For a prerecorded audio track including audio-only presentations,
provide at least one setting between 75% and 80% of the original
speed.
4. 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.
5. The user agent is not required to satisfy this checkpoint for
audio and animations whose recognized role is to create a purely
stylistic effect.
For all rendered content
Content type labels: Animation, Audio.
Note: Purely stylistic effects include background sounds, decorative
animated images, and effects caused by style sheets. The style
exception of this checkpoint is based on the assumption that authors
have satisfied the requirements of the "Web Content Accessibility
Guidelines 1.0" [WCAG10] not to convey information through style alone
(e.g., through color alone or style sheets alone). See checkpoint 2.6
and checkpoint 4.7.
4.5 Start, stop, pause, advance multimedia. (P1)
1. 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.
2. The user agent is not required to satisfy this checkpoint for
audio and animations whose recognized role is to create a purely
stylistic effect.
3. 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).
4. The user agent is not required to play animations during fast
advance and fast reverse.
5. When the user pauses a real-time audio or animation, the user
agent may discard packets that continue to arrive during the
pause.
For all rendered content
Content type labels: Animation, Audio.
Note: See checkpoint 4.4 for more information about the exception for
purely stylistic effects. This checkpoint applies to content that is
either rendered automatically or on request from the user. Respect
synchronization cues per checkpoint 2.6.
4.7 Slow other multimedia. (P2)
1. Allow the user to slow the presentation rate of audio and
animations (including video and animated images) not covered by
checkpoint 4.4.
2. The same speed percentage requirements of checkpoint 4.4 apply.
For all rendered content
Content type labels: Animation, Audio.
Note: User agents automatically satisfy this checkpoint if they
satisfy checkpoint 4.4 for all audio and animations.
4.8 Control other multimedia. (P2)
1. Allow the user to stop, pause, resume, fast advance, and fast
reverse audio and animations (including video and animated images)
not covered by checkpoint 4.5.
For all rendered content
Content type labels: Animation, Audio.
Note: User agents automatically satisfy this checkpoint if they
satisfy checkpoint 4.5 for all audio and animations.
11.5 Default binding requirements. (P2)
1. Ensure that the user agent default input configuration includes
bindings for the following functionalities required by other
checkpoints in this document:
+ move focus to next enabled element, and move focus to
previous enabled element;
+ activate focused link;
+ search for text;
+ search again for same text;
+ increase size of rendered text, and decrease size of rendered
text;
+ increase global volume, and decrease global volume;
+ stop, pause, resume, fast advance, and fast reverse selected
audio and animations (including video and animated images).
2. If the user agent supports the following functionalities, the
default input configuration must also include bindings for them:
+ next history state (forward), and previous history state
(back);
+ enter URI for new resource;
+ add to favorites (i.e., bookmarked resources);
+ view favorites;
+ stop loading resource;
+ reload resource;
+ refresh rendering;
+ forward one viewport, and back one viewport;
+ next line, and previous line.
For user agent features
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.
</quote1>
oh, and just so that it is clear what precisely the User Agent Accessibility
Guidelines (UAAG) 1.0 consider "animation", here is the definition provided
by the 14 July 2001 draft of that document:
<quote2>
Animation
In this document, an "animation" refers to content that, when
rendered, creates a visual movement effect automatically (i.e.,
without manual user interaction). This definition of animation
includes video and animated images. Animation techniques
include:
+ graphically displaying a sequence of snapshots within the
same region (e.g., as is done for video and animated images).
The series of snapshots may be provided by a single resource
(e.g., an animated GIF image) or from distinct resources
(e.g., a series of images downloaded continuously by the user
agent).
+ scrolling text (e.g., achieved through markup or style
sheets).
+ displacing graphical objects around the viewport (e.g., a
picture of a ball that is moved around the viewport giving
the impression that it is bouncing off of the viewport
edges). For instance, the SMIL 2.0 [SMIL20] animation modules
explain how to create such animation effects in a declarative
manner (i.e., not by composition of successive snapshots).
</quote2>
References:
1. 14 July 2001 Working Group Draft of the User Agent Accessibilty
Guidelines 1.0
URI: http://www.w3.org/WAI/UA/WD-UAAG10-20010714/
Received on Thursday, 26 July 2001 22:04:02 UTC