I’ve been having an interesting email discussion with Bruce D’Arcus and Richard Newman as a result of Bruce pointing us both at this posting on Metadata Interoperability by Kevin Clarke. I thought I’d write up some points to respond to that article here, in particular on the use (or lack of use) of RDF in the library community.
Presently there are a dizzying array of different metadata formats in the library sector, covering cataloguing, authority records, bibliographic metadata, etc. Examples include MARC, MARCXML, XOBIS, and MODS. There are also a number of different schemas in use in publishing sectors for describing research papers, conference proceedings and the like.
Very often there’s a lot of detailed data modelling that has formed the groundwork of these schemas. FRBR is an excellent example of this.
Increasingly these formats are being designed as XML schemas. Unfortunately, with an emphasis on XML Schema rather than RELAX NG. “Crosswalks” — a term I see in the library area, but little used elsewhere — are used to transform documents between various schemas, enabling some degree of interoperability. The success of these depend on the comparitive richness of the different formats; the usual loss of fidelity in transformations.
Clarke’s posting discusses the concept of a “switchboard schema”, an all embracing schema into which all the others can be converted with minimum loss of fidelity. Possibly backed by a “switchboard” that can negotiate the best path for a given end-to-end transformation.
I can’t help thinking, as did D’Arcus, “why not use RDF?”. Clarke’s response is interesting:
…I don
RDF and Library Metadata Interoperability
Published
Lost Boy 
RDF: Show Me the Money
Bruce D’Arcus and I have been sending some emails back and forth about my last post on metadata interoperability. In a comment on the original post, he suggests RDF instead of XSLT crosswalks. In my reply, I referenced Bill Moen’s tongue…
ldodds states:
RDF is essentially a relational model, although not in the classic RDBMS sense. This means its much easier, IMO, to clearly express a model in RDF.
Gary replies:
“a relational model”?
Codd and Date clearly defined _the_ relational model. RDF doesn’t fit the relational model.
ldodd states:
“RDF lets me avoid the nitty-gritty of physical data model design. I can concentrate on the logical model, and be confident that I can throw any RDF/XML instance document into a triple store without further configuration. I can also be confident that I can throw anyone else’s data into that store also, and further, that if we reference common resources (via URIs) that data will be immediately merged and available to me.”
Gary replies:
Every sentence of this is wrong. Sorry I don’t have time to explain everything, but you should be more careful about what you say, because it is so, so wrong.
This is a very interesting posting. Counting on RDF and OWL I’m trying to handle the metadata interoperability problem you described in one of the EU’s largest digital library projects. Would be interesting to share experience, results, etc. 🙂