RE: TT and subtitling/captioning - separating timing from style from content - temporal flow of content

Just a quick comment related to the timing semantics of John's example:

At 10:00 AM 8/7/2003 -0400, Glenn A. Adams wrote:

>I.e. - using example (crudely hatcheted from GA examples)
>
><seq>
><ref id="T27" dur="3s"/>
><ref id="T28" begin="T27.end " dur="3s"/>
></seq>
>
>If we support this idiom, then we would introduce a new element type cue 
>instead of using the SMIL ref element type. It would take a select 
>attribute that would use XPointer or XPath to select the content. Also, 
>your use of the begin attribute above is redundant, since the semantics of 
>seq imply that subsequent children follow immediately in time.

It's not only redundant, but syncbase-value begins are disallowed (among 
others) in children of a seq.
(See: http://www.w3.org/TR/smil20/smil-timing.html#Timing-SeqSyntax )