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(Action): Proposals and questions about "presentations" and "animations" [Issue 430]

From: Ian Jacobs <ij@w3.org>
Date: Wed, 24 Jan 2001 14:40:13 -0500
Message-ID: <3A6F2F9D.CBD9B424@w3.org>
To: w3c-wai-ua@w3.org
Hello,

Per our action item of the 9 Jan 2001 teleconference [1], Eric
and I have discussed the definitions of "animation",
"presentation" in light of issue 430 [2]. Please consider the
following proposals and questions based on that discussion. The
checkpoints in this email are those of the 16 Jan 2001 draft [3].

 - Ian

[1]
http://lists.w3.org/Archives/Public/w3c-wai-ua/2001JanMar/0071.html
[2] http://server.rehab.uiuc.edu/ua-issues/issues-linear-lc2.html#430
[3] http://www.w3.org/WAI/UA/WD-UAAG10-20010116/

-------------------------------------------------
Proposal 1: Delete the formal term "presentation"
-------------------------------------------------

A "presentation" may mean a number of things:

 - A series of status slides that together convey a story;
 - A video-only presentation (e.g., a silent movie);
 - An audio-only presentation (e.g., a radio show);
 - A synchronized collection of different pieces of content
   (e.g., created in SMIL).

   This last meaning is the one used in the glossary of the 
   16 January 2001 draft.

We might limit our usage of the term "presentation" to mean
"content with an inherent time component" (as opposed to one or
more static Web pages), but I don't think that we should. Rather,
I propose that:

a) We use the following terms instead of the catch-all
  "presentation": audio, video, animation, animated image,
   and synchronized content. I mention these because
   they (should) all appear in checkpoints 4.4 and 4.5.

b) We may use the term "presentation" in an informal manner
   (as one would in English) in UAAG 1.0, but we should
   avoid it where a particular meaning might be inferred.

c) We delete the term "presentation" from the glossary.

-------------------------------------------------
Proposal 2: About animations
-------------------------------------------------

Refer to email sent to Chris Lilley requesting info
on animations:
  http://lists.w3.org/Archives/Public/w3c-wai-ua/2001JanMar/0118.html

Suppose for the proposals below that the definition of "animation"
includes "animated images".

--------------------------
Proposal 3: Checkpoint 3.2
--------------------------

1) Do not broaden checkpoint 3.2 to include other animations
   than animated images:

  <OLD> 
     Allow the user to configure the user agent 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 activate each placeholder
     individually and replace it with the original
     author-supplied content. [Priority 1] 
  </OLD>

  Rationale: The "placeholder" requirements of 3.2 make it
  difficult to imagine how this would be done for animations
  in general, created through scripts, style sheets, and
  markup languages. Note also that the user can control a more
  general class of animations per the requirements of Guideline 4.

2) Change the content type label from "Animation" to "Image"
   (since this is only about animated images).

--------------------------
Proposal 4: Checkpoint 3.4
--------------------------

1) Delete "motionless," since this is only about blinking.

  <OLD>
   Allow the user to configure the user agent to render blinking
   images as motionless, unblinking images.
  </OLD>

  <NEW>
   Allow the user to configure the user agent to render blinking
   images as unblinking images.
  </NEW>

2) Change the content type label from "Animation" to "Image"
   (since this is only about animated images).

-------------------
Question about checkpoints 4.4/4.5/4.7/4.8
-------------------

Question: For checkpoints 4.4 and 4.5, are these checkpoints
intended to require control of synchronized multimedia
presentations?  Here are the checkpoints:

 --------
 4.4 Allow the user to slow the presentation rate of audio,
 video and animations. 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, video and
 animations whose recognized role is to create a purely
 stylistic effect. [Priority 1]

 4.5 Allow the user to stop, pause, resume, fast advance, and
 fast reverse audio, video, and animations that last three or
 more seconds at their default playback rate.  The user agent
 is not required to satisfy this checkpoint for audio, video
 and animations whose recognized role is to create a purely
 stylistic effect. [Priority 1]
 --------

Note also checkpoint 2.5:

 2.5 Respect author-specified synchronization cues during
 rendering.

This means that if the user slows down audio per checkpoint
4.4 and that audio is part of a synchronized presentation, then
the user agent should slow down the entire presentation
(respecting synchronization cues). Do other people have
the same understanding? 

So:

1) If 4.4 (and/or 4.5) includes control over synchronized content,
   should we make this clearer, or is the cross reference to  
   checkpoint 2.5 sufficient?

2) If 4.4 (and/or  4.5) does not include control over 
   synchronized content and only is about individual source sof
   video, audio, or animation, then should we make this clearer?

I don't have a proposal for changing 4.4 and 4.5; I await
feedback from the WG.

Proposal:

 - If animated images are a subclass of animations, then
   checkpoints 4.4, 4.5, 4.7, and 4.8 require addition of 
   the "Image" content type label.


-- 
Ian Jacobs (jacobs@w3.org)   http://www.w3.org/People/Jacobs
Tel:                         +1 831 457-2842
Cell:                        +1 917 450-8783
Received on Wednesday, 24 January 2001 14:40:16 GMT

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