[OAI-implementers] Qualified Dublin Core

Stephen Crawley crawley at dstc.edu.au
Wed Aug 11 22:36:06 EDT 2004


A canonical container XSD for qualified DC would be useful, but it
doesn't really solve the problem, IMO.

Why?  Because many (most) DC-based metadata collections use elements and/
or refinements that are not in DCQ.  These can be extensions mandated
by some other standard (e.g. AGLS, EdNA, etc) or site-specific
extensions. So, while oai schemas for exchanging DCQ, AGLS, EdNA, etc
would be useful, the larger problem is how to exchange metadata with an
arbitrary metadata schema ... without defining yet another XML schema
to transport the records.

The solution (as we see it) is to use XSD that is *insensitive* to the
metadata's schema.  In the simple model, the OAI repository assembles
XML records containing whatever elements it is prepared to publish. The
OAI client would then sort through the supplied elements, throwing away
any that it doesn't want / understand, and massaging others as required.
Then the client validates the filtered records against its own metadata
schema before it decides what to do with them.

The problem of elements meaning different things in different schemas
is a bit tricky.  However, you can get some traction if each record's 
metadata schema identifier is included in the record.

For info: I've attached the XSD schema that DSTC's MetaSuite system uses
for passing metadata records between Broker instances over OAI.  The XSD
is not suitable for general use because it contains a lot of MetaSuite
specific admin fields.  However, it illustrates the approach. The key
bits of the XML schema are the "schema" attribute and the "element"
element.  The latter represents the element's prefix + name + refinement
as the "id" attribute.

If anyone is interested in developing an OAI spec for schema-independent
metadata interchange, please drop me a line.

-- Steve

| Stephen Crawley                  | MetaSuite Project Leader
| Level 7, GP South Building (78)  | Distributed Systems Technology CRC
| Staff House Road                 | Tel   : +61 7 3365 4310
| The University of Queensland     | Fax   : +61 7 3365 4311
| Queensland 4072                  | Email : crawley at dstc.edu.au
| Australia                        | WWW   : http://www.dstc.edu.au
|                                  | DSTC is the Australian W3C Office

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