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Problems with proposed checkpoint on synchronized views

From: Ian Jacobs <ij@w3.org>
Date: Sat, 06 May 2000 15:09:33 -0400
Message-ID: <39146DED.ABD383E2@w3.org>
To: w3c-wai-ua@w3.org

At the 2 May teleconference we discussed a new requirement for
synchronized views. In trying to add a checkpoint 
to the document, I have come across the following questions:

1) What does it mean to synchronize a view? Is it any more than
   saying that the current focus in one viewport should follow
   the current focus in the other (as well as possible)? Are there
   other aspects to synchronization? I suspect not, for if the views
   must be exact duplicates always, I don't see the point of having

   Summary: Synchronized views means synchronized content focuses.

2) Which views should be synchronized? I believe that the user agent
   should <strong>not</strong> synchronize all views that happen to 
   refer to the same content. (In fact, it's even difficult to 
   say what we mean by "the same content". 
   What if two different URIs designate copies
   of the same document? The user agent should not be required to
   know that they are copies and that two views are rendering the
   same content from different resources). Even when I open two views
   for the same URI, I do not want the focuses to follow each other
   automatically. In fact, usually I don't want them to follow each 
   other since I opened two different views to navigate the same 
   content in two different ways. 

   Furthermore, synchronized focus changes may be disorienting 
   if the user is unaware that associated focuses are meant to 
   change together.

   Summary: Two views should automatically be synchronized simply
            because they display the same resource.

3) When does synchronization stop? Suppose I navigate to a form
   control and submit a form and the focus is following my
   actions in another view that also contains the form. Should the
   form be submitted in the second view? I don't think in the general
   case it should. What about following a link in one view - should
   the link be followed in the other view? What if the link isn't
   even visible (i.e., it's hidden since the renderings are 
   different)? When should the focuses cease to follow each other?

4) When do we want to require synchronization? We have heard some
   good examples of using synchronized views, such as synchronizing
   a link view with a primary view. In this case, the user should
   be able to navigate the links and would like the focus to follow
   in the primary view. That seems useful to me, but that happens 
   to be a useful feature provided by the user agent. How many
   synchronized views are we requiring? One? More than one? Which
   ones? As pointed out in point 2, I don't believe the answer
   should be "synchronize all views". If we only require one
   synchronized view, what should it contain? The links view
   mentioned above may be implemented through style sheets, and
   synchronized views in which users can adjust rendering is indeed
   a powerful tool. However, user agents aren't required to
   implement a links view with style sheets. Are we going to
   require any other views than the outline view?
   Summary: Other than the outline view, we don't require
            the user agent to offer any other views.
            Therefore, I don't see how we can require
            synchronization between views (other than the
            primary and outline views) when we don't
            know what the semantics of those views will be.

We have decided to require an outline view but have not
required that view to be navigable (though we have suggested
a navigable outline view would be a good thing). Do we wish
to now require that the outline view be navigable and that
the focuses should be synchronized? 

In short, I think that we need to reconsider the resolution to 
add a checkpoint requiring the user agent to synchronize views.
While synchronized views are certain powerful techniques for
navigation, I don't believe we have considered the problem 
fully enough to add a checkpoint this late in the process. I propose
instead that we explain view synchronization in the techniques 
document and provide the links view example.

 - Ian

[1] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000AprJun/0274.html
Ian Jacobs (jacobs@w3.org)   http://www.w3.org/People/Jacobs
Tel:                         +1 831 457-2842
Cell:                        +1 917 450-8783
Received on Saturday, 6 May 2000 15:09:44 UTC

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