RE: [Issue 517] Proposal to address nested time containers.

<quote> This is not practical
    with SMIL and SVG as this goes against the basic data models
    in the languages.</quote>

It seems to me that this is a very dangerous argument.  This is suggesting
that, if the language was designed in a particular way, then accessibility
issues need not be followed.  This is how we got into the current situation
to begin with.  The stronger argument is that, if the data model doesn't
allow for accessible design, it is broken!

The goal of the checkpoint is to reduce the complexity of the rendered page
for those individuals who cannot process information as rapidly, or who may
be distracted by complex pages with a number of things happening at once.

If control of the master time container allows overall complexity of the
page to be reduced or the presentation rate to be slowed, then that would
meet the demands of the checkpoint, IMHO.

Denis Anson

-----Original Message-----
From: []On
Behalf Of Ian B. Jacobs
Sent: Tuesday, July 03, 2001 12:38 PM
Subject: [Issue 517] Proposal to address nested time containers.


Based on discussions with Jon Ferraiolo and Dean Jackson at the
28 June 2001 teleconference [1] about issue 517 [2], I'd like to
propose the following to address this question: What do checkpoints
4.4 and 4.5 mean in the case of nested time containers? The original
comment [3] from the SVG WG was:

    [Checkpoint 4.4] talks about controlling particular
    animations on an individual basis. This is not practical
    with SMIL and SVG as this goes against the basic data models
    in the languages. In SMIL and SVG (and QuickTime), there are time
    containers which are masters over time-based content such as
    animations. The time container is the master that drives the
    as a slave. The animation just responds to commands such as "update
    yourself to what you should look like X.Y seconds into the
    The only thing that is reasonable is to allow the ability to pause,
    accelerate or decelerate the time containers.

[Editor's note: So far the checkpoint does apply to the SMIL 2 model.
 The SVG WG comments continue]

   However, if you have nested time containers, things can still get
   complicated as the nested time containers themselves are just slaves
   their parent time containers. Selecting these nested time containers
   require extensive user interface work on the part of UA developers
   would represent  large amounts of work just to support this


   - A user agent must provide the required control for each of the
     content types listed (audio, animations).

   - Checkpoint 2.6 already requires that the UA respect synchronization
     cues, so if the user controls two pieces of synchronized content
(one parent,
     one child, for example), they should behave in a synchronized


   - Added to checkpoints 4.4 and 4.5 that when the time frame of one
     is controlled by the time frame of another element, this checkpoint
     requires control over the master. This is a sufficient technique
     not necessary, as independent control of "slaves" would also
satisfy the

   - A user agent may also provide independent control of the "slave"

   - Add a SMIL example of this to the Techniques document.


 1) Reference draft: 22 June 2001:

The SVG makes an additional comment:

   A SMIL or SVG UA has no way of determining whether an animation can
  recognized as purely stylistic. In fact, in presentation-oriented
  like SMIL and SVG, it is often unclear where content ends and styling
  begins. It is meaningless to talk about UA not being required to
  the checkpoint for animations for purely stylistic effects as this is
  almost never recognizable.

Response: That's fine and that means the style part of the checkpoint
not apply. But that doesn't require any change to UAAG 1.0.

 - Ian

Ian Jacobs (
Cell:                    +1 917 450-8783

Received on Wednesday, 4 July 2001 08:03:55 UTC