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RE: SYMM WG comments on XBase 2nd last call

From: Jonathan Marsh <jmarsh@microsoft.com>
Date: Wed, 5 Jul 2000 09:14:07 -0700
Message-ID: <116DFD732FA92E4D9B647C8EEF6DAF1015E25B@red-pt-02.redmond.corp.microsoft.com>
To: "'Lloyd Rutledge'" <Lloyd.Rutledge@cwi.nl>, www-xml-linking-comments@w3.org
Cc: symm@w3.org, Paul Grosso <pgrosso@arbortext.com>, Patrick Schmitz <pschmitz@microsoft.com>
Thank you, this helps me to understand the importance of this feature.

I'd also like to get an impression of the urgency with which this feature is
being pursued.  Does the current version of SMIL have any base-like
functionality?  Does it appear on a "deferred to next version" list?  On a
SMIL-v.next wish list?  Has there been significant discussion within the

> -----Original Message-----
> From: Lloyd Rutledge [mailto:Lloyd.Rutledge@cwi.nl]
> Sent: Tuesday, July 04, 2000 12:24 AM
> To: www-xml-linking-comments@w3.org
> Cc: symm@w3.org; Jonathan Marsh; Paul Grosso; Patrick Schmitz
> Subject: Re: SYMM WG comments on XBase 2nd last call 
> Thanks for your support in having this re-examined, Jonathan.  Patrick
> Schmitz can communicate how important referential bases are better
> than I can.  My description of the issue is that in multimedia (SMIL)
> documents, much more than in hypertext (HTML) documents, there is the
> use of a large number of many different media types.  These different
> types vary greatly in how much bandwidth they use.  They also vary in
> how they are delivered, with the primary example being the growing use
> of streamed media.  Thus, it is common practice in multimedia for
> different media types to be distributed from different servers that
> are each specialized for distributing certain media types.  These
> different media types would be scattered throughout the SMIL
> hierarchy, since the SMIL hierarchy is determined by timing
> structure. Thus, you could not group common media types sharing common
> bases into hierarchies so that XBase as it currently stands could be
> used.
> Any SMIL presentation with streamed media, which I believe most have,
> will also have non-streamed media, such as images and text.  Streamed
> media needs to come from a streaming server.  Other media would more
> often be delivered from a static file server.  These documents would
> thus use at least two servers, perhaps more.
> Another use case is annotation, which many people looking into SMIL
> are considering using it for.  The media that is annotated and the
> media comprising the annotation would most likely come from different
> places.  Yet another use case comes from the use of the <switch>
> element to select a media object from alternative servers, in case the
> primary one is not available.  One could have switches through the
> document hierarchy separating primary from backup servers.
> The defining characteristic of multimedia is that is brings together
> many different types of media components and integrates them in what
> is often an intricate fashion.  It is this characteristic that makes
> referential bases so important for SMIL.
> -Lloyd
> On Mon, Jul 3 2000 Jonathan Marsh wrote:
> > Indeed it complicates things greatly.  The WG already 
> rejected this type of
> > functionality because of the level of complication 
> introduced.  But I think
> > re-examining this decision is warranted because of the new 
> information
> > revealed in this thread:
> > 
> > 1) SYMM may have use for this kind of capability.  Previously we had
> > considerred this only in the context of XHTML.  So we've 
> doubled the number
> > of "customers".
> > 
> > 2) The xml:base mechanism may not be suitable for extension 
> by languages
> > needing it, because a different media type (text/smil vs. 
> text/xml) may
> > produce different results.  If our design precludes 
> extension, we may want
> > to rethink a bit.
> > 
> > 3) Adding this in an XML Base 2.0 appears quite difficult.
> > 
> > I agree that this feature has a high complexity price tag, 
> and that a number
> > of workarounds exist.  I trust that SYMM will communicate 
> just how important
> > this capability is for them so we can evaluate the tradeoffs.
> --
> Lloyd Rutledge  vox: +31 20 592 41 27       fax: +31 20 592 41 99
> CWI             net: Lloyd.Rutledge@cwi.nl  Web: 
Post:   PO Box 94079   |  NL-1090 GB Amsterdam  |  The Netherlands
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Received on Wednesday, 5 July 2000 12:20:27 UTC

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