- From: Ian Jacobs <ij@w3.org>
- Date: Sun, 10 Sep 2000 20:01:57 -0400
- To: w3c-wai-ua@w3.org
Hello,
Per my action item of the 7 September 2000
teleconference [1], here is a proposal for
aligning the audio, video, and animation
requirements of Guidelines 3 and 4 with the
discussions during the last teleconference. This
email is in five parts: background, summary
of issues, proposals for guideline 3, proposals
for guideline 4, and a proposed new checkpoint about
accessible generated content. URIs are at
the end of the email. The checkpoint numbers
given here are those of the 1 September draft [2].
1) BACKGROUND
The previous time we had this discussion about
Guidelines 3 and 4 was 27 July [3]. At that time,
the Working Group adopted a proposal [4]
that I will summarize here:
1) Guideline three is about configuration and
global settings.
2) Guideline four is about element-level control.
The adopted proposal argued that element-level control
after a global "off" setting was unnecessary since
the user had the necessary control per Guideline 4.
However, at the previous teleconference, the
Working group asserted otherwise.
2) SUMMARY OF DISCUSSION
Our discussions have brought to light several
ideas that were not addressed in the previous
proposal:
2a) When there is a configuration not to render
some author-supplied content, the user must be
informed that this content is available but
not rendered.
2b) Typically, the way that user agents indicate
the absence of author-supplied content is with
placeholders.
2c) These placeholders must be accessible.
2d) Element-level control is indeed required after a
global configuration not to render some content
type. One reason for this (forwarded by Denis
Anson) is that N pieces of content rendered
together may not be accessible, but each one
may be accessible when retrieved individually.
2e) Automatic user agent behavior (in this case
rendering content) may not be accessible and there
needs to be a requirement to allow the user to
control the behavior manually. We already have
such requirements for form submission, page
refreshes, focus changes, etc. It is natural to
extend this reasoning to rendering: some content
rendered automatically may be inaccessible, and
and the Working Group has asked for a requirement
that the user be able to access it on demand only.
3) PROPOSALS FOR GUIDELINE THREE
Note: Checkpoints 4.5 and 4.6 combine audio,
video, and animations. For consistency, I will
combine some checkpoints of Guideline 3 similarly.
There are no proposed changes to checkpoints 3.4,
3.7, and 3.8.
3a) Add a technique for all configuration checkpoints
not to render some content that the user
agent may choose not to download this
content at all. This technique already
appears in some of the current checkpoints.
3b) Background images (checkpoint 3.1):
New:
Allow the user to configure the user agent
not to render background images. Allow
configuration to notify the user when a
background image is present but not rendered.
Note: When background images
are not rendered, user agents should
render a solid background color.
This checkpoint only requires control of
background for "two-layered renderings", i.e., one
rendered background (other than a solid
color) with all other content rendered "above it".
Comments:
- Delete the following note since already in
the guideline prose:
"Background images may make it difficult or
impossible to read superimposed text."
3c) Guideline 3 checkpoints about configuration
of audio, video, and animated images (old
checkpoints 3.2, 3.3, and 3.5)
New:
Allow the user to configure the user agent
not to render audio, video, or animated
images except on explicit request from the
user. Allow a second configuration so
that when this content is not rendered,
the user agent renders a substitute placeholder
in context. When placeholders are rendered,
allow the user to activate each placeholder
individually and replace it with the
original author-supplied content.
Note: This checkpoint applies to 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).
Activation of a placeholder is considered
an explicit user request to render the
original content. Refer also to checkpoints
in Guideline 4 about control of audio,
video, and animation.
Comments:
- Move the following note to the guideline prose:
"Audio may interfere with other sources of
sound such as the output of a speech
synthesizer."
3d) Guideline 3 checkpoint about configuration
of images (checkpoint 3.9).
New: Same as previous checkpoint (3c) except that
it's only about images and it's a priority 2
checkpoint.
3e) Guideline 3 checkpoint about configuration
for scripts and applets (checkpoint 3.6).
New: Allow the user to configure the user agent not to
execute scripts or applets. Allow
configuration to notify the user when scripts
or applets are present but not executed.
Note: This is particularly important for
scripts that 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.
Comment:
- I'd also like to move the note after the
checkpoint to the guideline prose or the
techniques document.
3f) Allow the user to configure the user agent
to render blinking images as motionless
images.
Comment:
- Addition control of blinking is not required.
Therefore, it is sufficient to stop the
blinking and render a motionless image instead.
4) PROPOSALS FOR GUIDELINE FOUR
Refer also to the previous proposal [5] for
changes to checkpoints in Guideline 4.
4a) Allow the user to stop, pause, resume, fast advance, and
fast reverse individual sources of audio, video, and animations
that last three or more seconds at their default
playback rate and that are not identified by the author
as style. The user must be able to control each source
recognized as distinct independently of others. [Priority 1].
Note: This checkpoint applies to content that is rendered
automatically or on request from the user. Respect
synchronization cues per checkpoint 2.4.
The user agent may satisfy this checkpoint by
allowing control of all audio, video, and
animations.
4b) Allow the user to slow the presentation rate
of individual sources of audio, video and animations
that are not identified by the author as
style. [Priority 1]
Note: The user agent may satisfy this checkpoint by
allowing the user to slow all audio, video, and
animations.
4c) Allow the user to stop, pause, resume,
fast advance, and fast reverse individual sources of
audio, video, and animations not covered by
checkpoint 4a [Priority 2].
4d) Allow the user to slow the presentation rate of
individual sources of audio, video, and animations
not covered by checkpoint 4b [Priority 2].
5) PROPOSAL FOR NEW CHECKPOINT ABOUT ACCESSIBLE
GENERATED CONTENT
In the 1 September Guidelines, checkpoint 2.7
(natural language) and checkpoint 2.5 (missing
text equivalents) require the user agent to
generate replacement content. The checkpoints
above also include a requirement to generate
placeholders (on configuration). I believe that
the Working Group has, up to now, assumed that any
content generated by the user agent in the
following circumstances must be accessible. I
propose to make this assumption explicit in the
following checkpoint:
<NEW>
Ensure that any content (i.e., any part of
the document object) generated by the user agent
conforms to the Web Content Accessibility Guidelines
1.0 [WCAG10]. This checkpoint is Priority 1 for
generated content that conforms Level A,
Priority 2 for generated content that conforms at
Level Double-A, and Priority 2 for generated
content that conforms at Level Triple-A.
Note: For example, if an image is used as
a place holder, ensure that the image has
a text equivalent per checkpoint 1.1 of
WCAG 1.0. Generated content includes content
that results from the repair of author-supplied
content (e.g., as required by checkpoint 2.5),
from a user configuration (e.g., refer to
checkpoint 2.7 and checkpoints in Guideline 3).
</NEW>
Comments:
- Checkpoint 1.3 of the ATAG 1.0 [6] reads:
"Ensure that when the tool automatically
generates markup it conforms to the W3C's Web
Content Accessibility Guidelines 1.0 [WCAG10]."
This ATAG checkpoint has a relative priority.
Thank you,
- Ian
[1] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0362.html
[2] http://www.w3.org/WAI/UA/WD-UAAG10-20000901/
[3] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0179.html
[4] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0022.html
[5] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0343.html
[6] http://www.w3.org/TR/2000/REC-ATAG10-20000203/
--
Ian Jacobs (jacobs@w3.org) http://www.w3.org/People/Jacobs
Tel: +1 831 457-2842
Cell: +1 917 450-8783
Received on Sunday, 10 September 2000 20:01:59 UTC