[OAI-implementers] RE: RDF, OAI, and application within Libraries
Joe Futrelle <email@example.com>
Mon, 21 May 2001 12:30:38 -0500
Exactly, and in fact in a distributed system there may be more than
one "normalized" format that metadata needs to be translated into. In
general, each "level 0" (maybe "level 1") tool will require a specific
format and may need to talk to other such tools through mediators
which can translate MD. The point is to maintain the semantics across
these translations. Thus whether or not a tool supports format X is
not critical; what's critical is whether it supports the relevant
semantics of format X, making translation possible.
On Fri, May 18, 2001 at 07:44:32AM -0400, firstname.lastname@example.org wrote:
> Regarding your data/service provider discussion. Yes, I agree that an
> individual party can play both roles, as you point out. In fact, in our
> above mentioned NSDL project we are doing exactly what you are saying -
> pulling in or using heuristics to extract very sloppy metadata from
> "level 0" data providers, processing it with computers and humans and
> then exposing via OAI as "normalized" metadata. This two-tier structure
> of data providers is very interesting to us in the sense that it
> provides a hierarchy for metadata enhancement - certainly an environment
> in which RDF plays an important role.
> > -----Original Message-----
> > From: Dave Reynolds [mailto:email@example.com]
> > Sent: Thursday, May 17, 2001 12:54 PM
> > To: lagoze@CS.Cornell.EDU
> > Cc: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org;
> > email@example.com; firstname.lastname@example.org
> > Subject: Re: RDF, OAI, and application within Libraries
> > Carl,
> > Many thanks for this - it helps me understand OAI's
> > positioning much better.
> > Let me paraphrase and respond to your points.
> > >  It is plausible to support non XML Schema means of
> > validating metadata
> > passed back from OAI queries but  too many options actually limits
> > flexibility by being too complex.
> > Agreed. You are right there are a lot of alternatives (Relax,
> > Schematron,
> > RDFS, DAML ...) and supporting everything it just too complex
> > and costly. In
> > my naive view of the world there are two useful extremes to support.
> > Firstly, one wants a tightly constrained validatable format suited to
> > typical metadata records. For that, XML Schema seems entirely
> > appropriate
> > and it's not obvious that going further and supporting Relax
> > or whatever
> > adds much.
> > Secondly, I believe that for future proofing we also need to
> > support less
> > formal semi-structured data formats. Semi-structured data
> > arises in many
> > ways - merging of multiple data sources, sparse user
> > annotations, rapidly
> > evolving schemas specific to given communities. In my simple
> > view of the
> > world RDF is a good foundation for a wide variety of
> > semi-structured data so
> > supporting that would be a useful complement to the highly structured
> > formats.
> > If this meant changing OAI to support an extra format I can
> > see that as an
> > extra complication. However, by using the sort of shallow (XML Schema
> > compatible) encoding we were discussing in this thread it
> > seems like RDF
> > could be supported as an incremental addition, within the
> > current framework,
> > and need not complicate implementations. There is the issue of using
> > RDFS/DAML schemas for interpreting the RDF when you get it.
> > However, even
> > these need not affect the OAI protocol since they are (a)
> > somewhat optional,
> > (b) can sometimes be inferred out of band e.g. from the
> > namespaces used in
> > the RDF properties, (c) could be included in the RDF payload.
> > To me these two extremes are sufficient between them to cover
> > most needs.
> > > An outstanding
> > > question for me is to understand where RDF sits in the OAI
> > data provider
> > > and service provider dichotomy.
> > An excellent point. Perhaps I am confused on the distinction
> > between data
> > providers and service providers but I can see repositories like DSpace
> > wanting to combine metadata from multiple sources and "smush"
> > them together
> > and also to support less structured metadata such as user or
> > small community
> > annotations. Their data provider role makes it appropriate
> > for them to use
> > OAI to export metadata access but they also have attributes
> > of a service
> > provider, or at least a clearing house for various metadata,
> > and so have
> > some role for these flexible semi-tructured metadata formats.
> > Dave
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