[vorbis] RDF Metadata Specification

Ralph Giles giles at snow.ashlu.bc.ca
Thu Aug 17 01:32:15 PDT 2000

On Wed, 2 Aug 2000, Robert Kaye (through our fearless leader) wrote:

> I've put together the first attempt to defining an RDF metadata
> vocabulary for use with the CD Index/MusicBrainz/OggVorbis. If you care
> about metadata issues, please take a look at:
>   http://www.cdindex.org/MM

Sorry I've taken so long in getting back to you about the second revision.
Part of the problem is I've been wallowing in documentation; there's a lot
more work and a lot less standard practice on this than I'd expected.

As I said, the current proposal is much better. I've been wanting to work
out the options for encoding our element set in xml before commenting in
too much detail, but that's proved complicated. There are a bazillion ways
to do it, even within RDF, and no recommended practice so speak of. I have
been thinking that full-on RDF is a bit complicated (hello Michael! :) for
the player interface and may suggest that we work with a stricter subset,
at least for Ogg. settle down. Maybe something along the lines of the
'encoding unqualified dublin core metadata in xml' working draft:


This would be upwards-compatible to the full standard, and just a
limitation on what can be in a particular file standard until things
settle down. This would mean, for example, just having a slew of
<dc:contributor> entries, without the <MM:Contributors><rdf:bag> wrapper
like in your 3rd example.

> However, I am sure that there are other things that I have not
> considered for the video case -- if there are things that you think need
> to get covered for video, please speak up!

The 'role' and 'roledetail' qualifiers are very clever. One issue with
film (or any large production, rather) is that there are often subgroups
under the credits, like "Malta Unit" or "Post Production". I'd suggest we
just use 'roledetail' for this, but maybe other options are better:

<dc:contributor role="Producer" roledetail="Executive">
  Herman Mayer


<dc:contributor role="Artistic Director" roledetail="Post Production">
  Laura NDualle

I like the second better.

Another issue is I don't think the x-DonutGopher thing makes sense. There
are *a lot* of roles credited in film, and they change over time. We can
try to maintain a canonical list with some mappings, but we'd always be
playing catch-up with the x-SystemsWranglers. Better not to try and accept
the chaos at the frontier. The industry itself will establish practice,
and we can follow that after the fact.

I suggest replacing MM:Album with a dc:relation link to a new resource.
These have to be separate records in your database anyway, and I think it
makes more conceptual sense to treat them separately in terms of metadata.
I'd been thinking you'd just dump the album metadata into a second
<rdf:description> section, but after writting the example below I think
you could get away without it.

<rdf:description about="http://cdindex.org/rdf/track.pl?id=6187">
  <dc:creator>Massive Attack</dc:creator>
  <dc:contributor mm:roll="Performer" mm:roledetail="vocals">
  <dc:relation dc:refinement="is part of"

<!-- and optionally -->

<rdf:description about="http://cdindex.org/rdf/album.pl?id=514">
  <dc:creator>Massive Attack</dc:creator>
  <dc:relation dc:refinement="has part"
  <dc:relation dc:refinement="has part"
  <dc:relation dc:refinement="has part"

I'm not clear on how free we are in what we put as the content of
the relation. Part of the point is to be human-readable, so I like
having the URL as a link attribute and using the title, but the parser
then has to know about the mm:link attribute (or perhaps a more general
xpointer-based one). In my naive understanding of RDF, we're supposed to
put the url as the content if we want to do this kind of cascading, and
the parser is supposed to be smart enough to look for
track->relation->title to get the album title. 

I did discover some parallel work, that might be interesting.

The dc-implementors list archive has some good information (as I imaging
do all the dc lists, but I haven't read them yet)


There have been a number of library-oriented efforts that should
dovetail nicely.

"An Indexing, Browsing, Search and Retrieval System for Audiovisual Libraries" 

"The Application of Metadata Standards to Video Indexing" 

I also  discovered that there are similar efforts going on as
part of mpeg7, smpte and some others:



giles at ashlu.bc.ca
Random acts of kindness are all very well, but one has to admire a well 
orchestrated, organised act of kindness.

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