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Re: Questions on event values

From: Leandro Marques Rodrigues <leandro@telemidia.puc-rio.br>
Date: Mon, 22 Mar 1999 14:29:19 -0300
Message-ID: <36F67DEF.9E2DEF4E@telemidia.puc-rio.br>
To: Lloyd Rutledge <Lloyd.Rutledge@cwi.nl>
CC: www-smil <www-smil@w3.org>
Lloyd Rutledge wrote:

> On Thu, Mar 18 1999 Leandro Marques Rodrigues wrote:
>
> > Imagine if the element E1 is
> > declared after the element that references it, for example:
> >
> > <seq>
> >    <ref begin="id(E1)(begin)" ... />
> >    <ref id="E1" .../>
> >    ...
> > </seq>
> >
> > The beggining of the first element depends on the beggining of E1, but
> > the beggining of E1 depends on the end of the first element. So, how
> > would the element seq behave?
>
> Such cyclic dependencies are clearly errors.  The solution here is
> simply for authors to avoid cyclic sychronizations relationships.
>
> > For me, the explicit begin of a child of a seq element should be
> > specified only related to the effective end of its ancestor (or the
>                                                      ^^^^^^^^
>
> This doesn't make sense.  The ancestor would be the <seq>.  Do you
> mean to refer instead to its previous sibling?

Yes, it's the previous sibling.

>
> > effective begin of the seq element, if it is its first child), and the
> > explicit begin of a child of a par element should be specifed only
> > related to the effective begin of the par element itself or of any other
> > child.
>
> What you describe are the typical situations for which synchronization
> would be used on the children of <seq>'s and <par>'s.  It is for this
> reason that what you describe is the default interpretation of the
> values of begin and end attributes when they are simply delay values.
> It seems that what you are arguing for is, using the language of the
> spec, the removal of "element-event values" (relative synchronization)
> from begin and end attributes.  Clearly, for the sitations you
> describe, authors should use delay values, which is what they are
> there for.  But presentations do often have more complex
> synchronizations needs for which element-event values are appropriate.
>
> -Lloyd
>
> --
> Lloyd Rutledge                              vox: +31 20 592 41 27
> CWI (Centrum voor Wiskunde en Informatica)  fax: +31 20 592 41 99
> PO Box 94079                                net: Lloyd.Rutledge@cwi.nl
> NL-1090 GB Amsterdam, The Netherlands       Web: http://www.cwi.nl/~lloyd

Ok. Thank you.

Leandro
Received on Monday, 22 March 1999 12:25:03 GMT

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