[OAI-implementers] Sample DCQ RDF via OAI

[Thomas G. Habing]

Hi all,

We have developed a set of XML Schemas that will allow validation (at least
using XSV) of RDF files containing multiple namespaces, such as Dublin Core
and Qualified Dublin Core.  Our set of XML schemas consist of a XML schema
for RDF, plus several XML schemas for the various namespaces (like DC and
DCQ) to be used as properties and types within the RDF.  These other schema
all rely on importing the RDF schema (which can result in redundant imports
which is allowed by the W3C XML Schema spec, though not by beta version of
MS XML parser).  Our XML Schema for RDF was written solely to facilitate OAI
compliance when multiple arbitrary namespaces need to be combined;
therefore, its content models are fairly loose.  In any case, XML Schema is
not really adequate to validate complete compliance to the RDF Model and
Syntax spec.

To demonstrate use of RDF and multiple namespaces we have a sample OAI 1.1
provider site.  It can be accessed at
http://bolder.grainger.uiuc.edu/oaisimple1.1/oai.asp?verb=Document  The site
contains 53 sample records in two sets.  The idli:dimti:dchc records (50)
are fairly simple, using only RDF, DC, and DCQ namespaces, whereas the
idli:acm records (3) are more complex, invoking several additional
namespaces plus more complex RDF structures.  The metadata prefix needed to
access the RDF metadata is 'uiuc_dcq_rdf'.  We've run the site and most of
the records through the Repository Explorer to verify compliance with OAI
1.1.

Note that some of the idli:acm examples make use of the MathML namespace to
preserve mathematical constructs within content like titles and abstracts. 
We avoided having to create an XML schema for MathML by allowing in our RDF
XML schema a content model of "<xsd:any namespace="##any"
processContents="lax"/>" for any RDF property element. The value 'lax' means
that if a schema is identified for the namespace, the parser will attempt to
validate using that schema, but it will not complain if a schema cannot be
found.

Regarding our use of RDF: We followed the preliminary DCMI guidelines for
"Expressing Qualified Dublin Core in RDF" (still being redrafted).   We used
the May 3rd draft of this document, but we think we're still generally
consistent with the redraft released earlier this week
(http://www.mathematik.uni-osnabrueck.de/projects/dcqual/qual21.3.1/).  We
need to recheck URLs used for various DC Namespaces, but it looks like
convergence on this document is being reached (fingers crossed).  Please
keep in mind that conventions for expressing DCQ in RDF (and conventions for
using RDF in general) are still soft (RDF Model and Syntax spec is being
updated as we write this).  We think the examples we put together are
reasonable, but certainly they're not definitive.  Use them as a model at
your own risk.  (Much better to start with the DCMI redraft guidelines
mentioned above.  Better yet to wait?)

Tom Habing
Tim Cole

-- 
Thomas G. Habing
Research Programmer, Digital Library Initiative
University of Illinois at Urbana-Champaign
052 Grainger Engineering Library, MC-274
thabing@uiuc.edu, (217) 244-7809