In March 2006, the DCMI Directorate awarded a contract to Andy Powell and Pete Johnston (both Eduserv Foundation, UK) to draft a revision of the existing DCMI specification for implementing Dublin Core in XML [1].
The result of this work is a new working draft titled "Expressing Dublin Core metadata using XML"
http://dublincore.org/documents/2006/05/29/dc-xml/
which will be available for comment by 17:00 EST on Tuesday, 30 May.
As described in DCMI's "Procedure for approval of DCMI metadata terms and recommendations" [2], proposals subject to Public Comment are announced on DC-GENERAL and posted on the DCMI Web site for a period of at least four weeks. During that time, any interested member of the public may submit a comment, either publicly to a DCMI mailing list such as DC-ARCHITECTURE, non-publicly through DCMI Feedback ([log in to unmask]), or directly to the issuer of the announcement.
About the document
==================
This document specifies an XML format for representing a DC metadata description set; this format is referred to as "DC-XML".
More details of the background to this work and the factors that influenced the design of the format are provided in the "release notes" available at
http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLReleasenotes/2006-05-29
The primary motivation for the work was to provide an XML format which was based on the DCMI Abstract Model [3], and which provided an XML serialisation for all of the constructs of the DCAM (or at least for some well-defined subset).
Some points to note:
- The DC-XML format is based on the DCAM and provides an XML serialisation for all features of the DCAM. It provides support for the following features which are not part of the models defined by the current DCMI recommendation for expressing DC metadata in XML:
- description sets, and the provision of multiple descriptions
- related descriptions
- resource URIs
- value URIs
- distinction between syntax encoding scheme URIs and vocabulary encoding scheme URIs
- provision of multiple syntax encoding scheme URIs and a single vocabulary encoding scheme URI within a single statement
- provision of multiple value representations within a single statement
- rich representations
- The DC-XML format is a different XML format from that specified by the current DCMI recommendation for expressing DC metadata in XML. In the general case, it is not possible to map between the two formats. For the "simple DC metadata record" model described in the current specification, such a mapping is possible (assuming agreement is reached on a mapping between that model and the DCMI Abstract Model); but for the "qualified DC metadata record" model, the construction of such a mapping is problematic (e.g. because that model does not distinguish between vocabulary encoding schemes and syntax encoding schemes or between value URIs and value strings)
Some issues/questions which arose during this work included
- the set of DCAM constructs to be supported: the choice was made to support all the constructs of the DCAM, though this adds some
complexity/"verbosity" to the format.
- the representation of URIs using XML QNames: the current draft allows some, but not all, types of URI used in the DCAM to be represented as XML QNames.
- the choice of XML element/attribute names: the current draft uses names which approximate the terms used in the DCAM, but this does result in some long element/attribute names.
XML Schemas
===========
A draft set of W3C XML Schemas for the DC-XML format is also available. Currently the schemas are available only as attachments to pages in the DC Architecture wiki, but once stable, they would be assigned persistent URIs on the main dublincore.org Web site. The design and use of these schemas is described in a separate note titled "DC-XML and W3C XML Schema":
http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLSchema/2006-05-29
This document is separate from the working draft above, but comments on these notes and on the XML schemas are also invited.
GRDDL
=====
A draft XSLT transformation from DC-XML to RDF/XML (i.e. a transform that could be used to support GRDDL [4]) is available, currently as an attachment to the Wiki page
http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLXSLT/2006-05-29
at
http://dublincore.org/architecturewiki/DCXMLRevision_2fDCXMLXSLT_2f2006_2d05_2d29?action=AttachFile&do=get&target=dcx2rdfxml.xsl
This transform is currently incomplete, but it will be developed further to reflect the content of the current working draft, and current DCMI guidance for expressing DC metadata using RDF.
Pete
[1] Guidelines for implementing Dublin Core in XML
http://dublincore.org/documents/dc-xml-guidelines/
[2] Procedure for approval of DCMI Metadata Terms and Recommendations
http://dublincore.org/usage/documents/approval/
[3] DCMI Abstract Model
http://dublincore.org/documents/abstract-model/
[4] Gleaning Resource Descriptions from Dialects of Languages (GRDDL)
http://www.w3.org/TeamSubmission/grddl/
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Pete Johnston
Technical Researcher, Eduserv Foundation
Web: http://www.eduserv.org.uk/foundation/
Email: [log in to unmask]
Tel: +44 (0)1225 474323
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