Ivan’s private site

February 13, 2007

Dublin Core abstract model

Filed under: Semantic Web,Work Related — Ivan Herman @ 11:09

The DCMI has published a draft for public review for an updated version of Dublin Core Abstract Model. From a Semantic Web point of view, the most important point about the new version is to have a clear association to RDF and RDFS terms as well as an alignment of the two models. For a vocabulary that is, as far as I know, the most widely used set of terms on the Semantic Web (after the core rdf, rdfs and owl terms, that is), this is really important. Actually, some of the “core” dc terms may also have new versions soon (in different name spaces) with more clearly defined rdfs:range and rdfs:domain, new class defitions, etc.

However… it is not all that simple and that is why it is still a draft. For good reasons: the DC community is old (in Internet terms, that is), it actually predates the Semantic Web activity at W3C, for example, which means that there are subtle but important differences in the models. An example for what I have seen is DCAM’s view of property values. In DCAM, it is possible for a property to have, say, a literal value and, at the same time, a URI value as well. An example I got from Tom Baker is (using DC’s textual syntax):

DescriptionSet (
  Description (
    ResourceURI ( <http://dublincore.org/pages/home> )
      Statement (
       PropertyURI ( dc:publisher )
       ValueURI ( <http://example.org/agents/DCMI> )
        ValueString ( "Dublin Core Metadata Initiative" )
)))

Which, in my reading, translates into something like:

<http://dublincore.org/pages/home> dc:publisher [
    rdf:value "Dublin Core Metadata Initiative";
    somepredicate <http://example.org/agents/DCMI>.
].

This means that the range of the dc:publisher should be some sort of a union of a pure Literal and some other class representing this URI+value structures. This can be done with OWL, though…

There may be other differences as well. If anybody is interested in the public comments, there is a mail on swig with further details; you can also look at the mail archives of the discussion. It is an important discussion to keep an eye on!

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