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Proposals for guidelines 3 and 4

From: Ian Jacobs <ij@w3.org>
Date: Sun, 10 Sep 2000 20:01:57 -0400
Message-ID: <39BC20F5.3CA19057@w3.org>
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 GMT

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