1. XML Schemas for Dublin Core Metadata
Pete Johnston, UKOLN, University of Bath
DC Architecture WG Meeting, DC-2004,
Shanghai, China, Wednesday 13 October 2004

2. XML Schemas for Dublin Core Metadata
Guidelines for Encoding DC in XML
Conventions for representing DC metadata in XML
Two sets of schemas
Simple DC only (simple content model, used by OAI-PMH oai_dc schema)
Qualified DC (more flexible content model, used by various implementers)
Versioning
Container elements
The “simpleLiteral” type
Abstract Model

3. Versioning
Terms are continually added to the DCMI metadata vocabularies as result of Usage Board decisions
DC Terms vocabulary
DCMI Type Vocabulary (?)
Requires changes to corresponding XML Schema to provide XML component declaration
XML Schema used for structural validation
Change to XML Schema may change validity of instance
e.g. <dcterms:provenance> XML element invalid on Friday night, valid on Monday morning

4. Versioning Currently Request to be able to reference “latest version”
URLs of all XML Schemas include datestamp
User references specific version
Must change references to access new version
Request to be able to reference “latest version”
Proposal
Make available both “latest version” and “date-stamped” versions
Impact
Applications choose which to reference
N.B. Must manage expectations re validation accordingly

5. Container XML elements
DC-in-XML Guidelines do not require use of specific XML container element
Applications choose XML container element
Request to provide container XML element(s) associated with DCMI XML Namespace
Proposal
Provide container XML elements corresponding to description and description set in DCMI Abstract Model
Question
Separate container XML elements for Simple DC description and Qualified DC description?
Or same XML element with different content models?
What XML Namespace should be used?
Also N.B. DC-in-XML doc adopts more restrictive notion of Qualified DC than DCMI AM

6. SimpleLiteral Datatype
dc:SimpleLiteral complexType defined so as to provide flexibility
Derive types based on simpleContent
Derive types based on complexContent (with child elements)
Derivation of complexType with simpleContent from complexType with complexContent allowable in XML Schema
But not supported by some parsers/processors
Questions from implementers
Some implementers do make use of derived types based on complexContent

7. DC-in-XML Guidelines and DCMI Abstract Model
(Not strictly a “schema issue”!)
DC-in-XML guidelines pre-date DCMI Abstract Model
Based on a simpler model of a DC metadata description
Do not support
resource URIs
value URIs
rich values
related descriptions
resource class URIs
Value strings sometimes being interpreted as value URIs

8. DC-in-XML Guidelines and DCMI Abstract Model
Either
Accept/emphasise current limitations Or
Decide which features of DCMI AM should be supported in syntax
Revise syntax accordingly (e.g. to distinguish value strings and value URIs)
Produce new set of schemas

9. Acknowledgements
UKOLN is funded by the UK Museums, Libraries and Archives Council (MLA), the Joint Information Systems Committee (JISC) of the UK higher and further education funding councils, as well as by project funding from the JISC and the European Union. UKOLN also receives support from the University of Bath where it is based.

10. XML Schemas for Dublin Core Metadata
Pete Johnston, UKOLN, University of Bath
DC Architecture WG Meeting, DC-2004,
Shanghai, China, Wednesday 13 October 2004