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Towards an event model for SMIL

From: Jennifer L. Beckham <beckham@research.att.com>
Date: Wed, 31 May 2000 11:59:04 -0400
To: "smil" <www-smil@w3.org>
Cc: "Nils Klarlund" <klarlund@research.att.com>
Message-ID: <FDELIFAEDLILEIJDJLJOOEEECAAA.beckham@research.att.com>
hello SMIL people:

Here at AT&T Research, we've been looking at SMIL as a way of handling
timing constraints for speech applications.  The orthogonal time
containers (par, seq, and excl) within SMIL’s Timing and
Synchronization Module provide us with a good foundation for
developing intricate speech-aware multimedia systems.  We're working
from a programming language point of view and have started on a formal
semantics for SMIL’s Timing Module.

Part of our process involves gaining a understanding of the states and
transitions for a given time container.  We found the section titled
“State Transition Model” in the Timing Module working draft
helpful, but also a bit confusing. Our greatest struggle was in
matching up the state diagram for an element with the informal
semantics in the draft.  In particular, the diagram does not very
clearly explain relationships with parent containers, synchronization
with other elements, and the evolving SMIL event model.

So, we've tried to define an event flow and state machine semantics
for SMIL. We try to elucidate the timing and the scheduling properties
of elements by separating the sync-arc relationships of elements from
the activation and playing of an element. Our work is summarized in
the attached html document.  Basically, we wanted to turn the state
diagram into something that precisely explains fundamental parts of
SMIL.  For this reason, we are using a simple event oriented model,
where the state diagram is a Mealy machine that define fundamental
concepts such as durations.

We would be very happy to receive comments on the model; have we
understood SMIL?

Thank you,
Jennifer L. Beckham
Nils Klarlund

(image/gif attachment: interaction.gif)

(image/gif attachment: state.gif)

Received on Wednesday, 31 May 2000 12:00:19 UTC

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