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Draft of ''Expressing Dublin Core metadata using XML'' released for comment

Introduction

DCMI is releasing for public comment the Working Draft Expressing Dublin Core metadata using XML [DC-XML].

Background

In March 2005, DCMI published the DCMI Abstract Model (DCAM) as a DCMI Recommendation. The DCAM describes the constructs that make up a DC metadata description set.

In order to represent a DC metadata description set in an XML document those constructs have to be represented as components in that XML document, i.e. as XML elements and XML attributes, XML element type names and XML attribute names, and as XML element content and XML attribute values.

The current DCMI recommendation for expressing DC metadata using XML, Guidelines for implementing Dublin Core in XML (XML-GUIDELINES) pre-dated the development of the DCAM. That document provides its own "abstract models" for a "simple DC metadata record" and a "qualified DC metadata record". However, those two models differ from the model described by the DCAM, both in the types of construct present, and in the labels used for essentially similar constructs.

For the "simple DC metadata record", it is possible to provide a mapping from that model to (a subset of) the DCAM, so that an XML document constructed using the former model can be interpreted in terms of the DCAM.

For the "qualified DC metadata record" model, the construction of such a mapping is problematic, mainly because that model does not distinguish vocabulary encoding scheme URIs from syntax encoding scheme URIs or value URIs from value strings (DCXML-DCAM).

So, the current situation presents two problems:

• DCMI currently provides no guidance for implementers who wish to express DCAM metadata description sets using XML.

• In the general case, XML instances constructed using the current guidelines for expressing DC in XML do not have a well-defined interpretation in terms of the DCAM.

Developing the new draft

In March 2006, the DCMI Directorate awarded a contract to Andy Powell and Pete Johnston (both Eduserv Foundation, UK) for a revision of the existing guidelines for implementing Dublin Core in XML.

The result of this work is a new draft document Expressing Dublin Core metadata using XML [DC-XML], which specifies an XML format for representing a DC metadata description set; this format is referred to as "DC-XML".

The following principles were applied in the design of this XML format:

• The format should provide a serialisation of all the features of the "Description Model" of the DCAM, i.e. it should be possible to represent all the constructs that make up a DC metadata description set.

• The format is not required to address the features of the "Schema Model" of the DCAM. For example, it is not required to express subproperty relationships between properties, subclass relationships between classes, etc.

• The format should be easily usable with XML-based specifications such as XPath, XPointer and XQuery, i.e. for each construct in the DCAM there should be a mapping to exactly one construct in the XML syntax.

• The format should not be dependent on features of a single XML Schema language.

• It should be possible to describe the format using W3C XML Schema [XMLSCHEMA], but it is not a requirement that when the format is used to serialise description sets conforming to a DC Application Profile, all the constraints expressed in a DC Application Profile are captured using W3C XML Schema.

Points to Note

• The DC-XML format is a different XML format from that specified by the current XML guidelines recommendation. In the general case, it is not possible to map between the two formats: for the "simple DC metadata record" model, such a mapping is possible; but for the "qualified DC metadata record", it is not.

• 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 XML guidelines recommendation:

• 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

• A set of W3C XML Schemas for the DC-XML format is available. The design and use of these schemas is described in the document DC-XML and W3C XML Schema [DC-XML-SCHEMA]

Request for Comments

The new draft document Expressing Dublin Core metadata using XML [DC-XML] is available for public comment.

Comments of a technical nature should be sent to the DC-ARCHITECTURE@jiscmail.ac.uk mailing list; more general comments may be sent to the DC-GENERAL@jiscmail.ac.uk mailing list.

References

[DCAM]
DCMI Abstract Model
http://dublincore.org/documents/abstract-model/

[XML-GUIDELINES]
Guidelines for implementing Dublin Core in XML
http://dublincore.org/documents/dc-xml-guidelines/

[DCXML-DCAM]
DC-XML and the DCMI Abstract Model
http://www.ukoln.ac.uk/metadata/dcmi/dc-xml-issues/

[DCXML]
Expressing Dublin Core metadata using XML. Working Draft of 2006-05-29.
http://dublincore.org/documents/dc-xml/2006-05-29/

[XMLSCHEMA]
XML Schema Part 0: Primer Second Edition. W3C Recommendation 28 October 2004.
http://www.w3.org/TR/xmlschema-0/

[DC-XML-SCHEMA]
DC-XML and W3C XML Schema. Draft of 2006-05-29.
http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLSchema/2005-06-29

Immutable page (last edited 2006-05-26 10:49:29 by PeteJohnston)