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Re: SYMM WG comments on XBase 2nd last call

From: Jonathan Marsh <jmarsh@microsoft.com>
Date: Fri, 30 Jun 2000 16:39:16 -0700
Message-ID: <116DFD732FA92E4D9B647C8EEF6DAF1015E252@red-pt-02.redmond.corp.microsoft.com>
To: "'www-xml-linking-comments@w3.org'" <www-xml-linking-comments@w3.org>, "'Lloyd Rutledge'" <Lloyd.Rutledge@cwi.nl>
Lloyd wrote:
> 1) XBase as a recommendation fits into SMIL because SMIL is XML. 
> We will not make any specific restrictions on the use of XBase 
> with SMIL. 

I'm glad to hear this, although I'm not sure it will provide you with XML
Base functionality.  If relative SMIL media URLs are to be resolved against
xml:base attributes, the SMIL spec must state this explicitly.  XML Base
provides a means for specifying the base URI, but not for recognizing URLs
in arbitrary XML content.  To support XML Base, the SMIL spec should
identify which attribute values and content represent URIs and state
explicitly that XML Base should be honored when dereferencing these URIs.
As an example, xlink:href attribute values are recognized as URIs and the
XLink spec states that they are resolved against xml:base.

> 2) We request the SML Linking WG to consider adding referential XBase
> functionality to the current draft, or a later version. We will not make
> this a requirement for using XBase with SMIL, however.

I presume this emerges from the desire to provide multiple "classes" of base
URI in a document - something akin to xml:video-base, xml:audio-base,
xml:stylesheet-base.  Admittedly the structure of the XML document will
often not have a 1-1 correspondence with the desired hierarchy of base URIs.
The linking WG considered this capability and for simplicity stuck with a
single generic base.  We will reexamine this issue in light of your request.

Does the following syntax proposal illustrate your request?

  <a xml:base="http://www.media.com">
    <mediabase id="video" xml:base="/daily/video"/>
    <mediabase id="audio" xml:base="/daily/audio"/>
    <b xml:baseref="video">vid1</b>
    <c xml:baseref="audio">aud1</c>
  </a>

b = http://www.media.com/daily/video/vid1
c = http://www.media.com/daily/audio/aud1
(and "id" is of type ID).

Of course, there are circularity problems with this particular approach...

> 3) If the XBase recommendation does not have referential functionality,
then
> we may use XBase and add SMIL specific referential functionality to it.

XML Base is designed to be available generically to text/xml and
application/xml documents.  If SMIL is using a different media type, it can
describe any mechanism for embedding base URIs in the document that it
wants.  If however, you plan to deliver SMIL documents as either text/xml or
something like text/smil-xml then it seems like even non-text/xml SMIL
documents should recognize XML Base, and only XML Base, to retain
interoperability.

At this point I don't see how augmenting XML Base could work, although I
look I look forward to any ideas you have on the subject.

- Jonathan Marsh
Received on Friday, 30 June 2000 19:41:33 GMT

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