Some comments below.

On Thu, 10 Feb 2005, Rachel Heery wrote:

> (sorry for X-posting, can WG chairs indicate on which list this discussion
> is best placed?)
>
> On Thu, 10 Feb 2005, Andy Powell wrote:
>
> >
> > Owners of such terms have to explicitly acknowledge that the terms are RDF
> > properties (or at least declare them in such a way that they are able to
> > be treated as RDF properties) before they can be used in DC application
> > profiles.  In practice, I suggest that this means that the semantics of
> > these terms should be declared using RDFS.
>
> I think your bracketed statement needs more explanation... it would be
> helpful to be clear as to how terms can be 'declared in such a way' that
> they can be used as RDF properties. Even allowing for the constraints of
> the DC data model, there seems to me some wriggle room to enable mixing
> and matching where 'owners' of terms are willing to co-operate.

Pete and Andy had agreed (as part of Usage Board work) to put together a
paper explaining better what this means, why MODS elements cannot be used
as RDF properties, and what needs to be done to be able to reuse MODS
elements. After all, those that are referenced in the DC-LAP are exactly
the semantics that were needed for the given element. I still don't
understand this completely.

> As I understand it the process for re-use of MARC relator terms was an
> initial agreement that (some of) the relator terms would be useful within
> DC records, then going through the formality of 'declaring' such terms as
> RDF properties - not trying to match the MARC data model to DC data model.
>
> ......
> .....
>
> > As an example of how this can work I would cite the MARC relator terms -
> > where the Library of Congress have taken (are taking?) the time to
> > explicitly re-declare an existing set of terms as RDF properties.
> > Because this has been done, it is now (or very soon will be) possible to
> > use the MARC relator terms in a DC application profile and for that usage
> > to be maningful in terms of the DCMI Abstract Model.
> >

And this was possible because we spent some time fitting our descriptions
of relator terms/codes into a form acceptable to UB members-- just
figuring out what to call the various elements that describe these
terms/codes (e.g. rdfs:label, rdfs:comment, etc.). Now our RDF expression
of relators is generated on the fly from our official documentation by
using stylesheets. It's a fairly mechanical process. And we didn't change
the list that we've been using for 30 or so years.

> I think it is the fact that the owner is willing to declare these
> terms 'outside' the rest of the MARC data model, as RDF properties that
> makes it ok to mix and match? within the MARC data model and MARC records
> the relator terms do not act as 'properties' as I understand it - the
> terms have a different role in MARC records than within DC records.
>
> This seems to make declaring terms as RDF properties something of a
> formality - as long as the maintainer or 'owner' of data element sets is
> willing to declare a particular sub-set of terms as RDF properties then
> that is ok...
>
> In my view the criteria for re-use of terms should be something like:
>
> "First, are the semantics and context of a term in one metadata format
> sufficiently similar to the semantics and context of the property I want
> to express in a DC description? if so can this term be usefully used in
> 'isolation' within a DC description out of the context of its original
> format?
>
> Second, are the 'owners' of the terms willing to co-operate?"

I would think in the case of these MODS elements the answer to both of
these is yes.

> If the answer to both of the above is yes, then declaring those terms as
> RDF properties may well be achievable. Especially if, as I understand has
> happened with MARC relator terms, just the sub-set of terms required from
> the 'other' format based on a different data model need to be declared??
>
> Maybe worth thinking about that old saying 'everything can be solved by a
> level of indirection'.... not knowing much about MODS, but could a sub-set
> of MODS terms be 'separated out' of MODS and declared as RDF properties?

Some of the MODS elements have equivalent DC elements. I suppose any such
subset would be those that are needed by an application profile?

In the case of Relators, we have an RDF expression of the whole list (as I
said above, generated on the fly) and only a subset has the statement that
it refines dc:contributor. We would need some guidance on how to do
this. Or perhaps there are tools to convert an XML schema to an RDF
one?

> In my view we should be looking for solutions to help us meet requirements
> of several user communities, and to move forward as regards the evolution
> of data element sets by allowing re-use of data elements. If this can be
> done by declaring sets of terms in RDFS then good....

Right, and this was the basis I think of Rachel's famous paper about
mixing and matching elements in different metadata schemas. Why redefine
something that has the same semantics if there's a way of just cooperating
instead?

Rebecca
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^  Rebecca S. Guenther                                   ^^
^^  Senior Networking and Standards Specialist            ^^
^^  Network Development and MARC Standards Office         ^^
^^  1st and Independence Ave. SE                          ^^
^^  Library of Congress                                   ^^
^^  Washington, DC 20540-4402                             ^^
^^  (202) 707-5092 (voice)    (202) 707-0115 (FAX)        ^^
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k

> Rachel
>
>
> ---------------------------------------------------------------------------
> Rachel Heery
> UKOLN, University of Bath                       tel: +44 (0)1225 386724
> http://www.ukoln.ac.uk
>