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Executive Summary

The term Dublin Core refers to set of metadata elements intended to represent information that is "core" across all knowledge domains. It is frequently referred to as a "lowest common denominator" metadata format, and is often used as a base metadata format for cross-collection searching.

What It Is

The Dublin Core Metadata Element Set (officially DCMES, but commonly called DC) emerged from a 1995 meeting hosted by OCLC in Dublin, OH, considering problems of finding information on the Web. Under the auspices of the Dublin Core Metadata Initiative (DCMI), Dublin Core as a metadata format has grown and developed over time. Currently, Dublin Core exists in two "flavors," Unqualified Dublin Core (also known as Simple Dublin Core) and Qualified Dublin Core.

Simple Dublin Core
Simple Dublin Core is a set of 15 metadata elements that represent "a core set of elements likely to be useful across a broad range of vertical industries and disciplines of study." [DCMI FAQ] All fields are repeatable; none are required. The 15 metadata element set has been approved as ANSI/NISO standard Z39.85 and ISO standard 15836.

Qualified Dublin Core
Qualified Dublin Core consists of the 15 elements from Simple Dublin Core, along with additional elements, element refinements, vocabulary encoding schemes, and syntax encoding schemes. DCMI-endorsed qualifiers are found on the DCMI Metadata Terms list. Most software implementing Dublin Core, including DSpace, OCLC Connexion, and CONTENTdm, uses a version of Qualified Dublin Core that adds custom qualifiers to the officially-endorsed options. DCMI encourages local extension of Dublin Core, but appropriately warns that local extensions will not be understandable by others.

The DCMI endorses several encodings of the element set. Simple name/value pairs may appear in <meta> tags in HTML Web pages. Both simple and qualified Dublin Core may also be encoded both in XML and in RDF. Libraries most frequently use the XML encoding, or store Dublin Core metadata in a relational database.

The most recent major development in the Dublin Core landscape was the release of the DCMI Abstract Model which defines "a reference model against which particular DC encoding guidelines can be compared." [DCMI Abstract Model] All current proposals before the Dublin Core Usage Board are considered in light of the Abstract Model. While the conceptual rigor enforced by the Abstract Model is commendable and its use will almost certainly result in more precise metadata, this rigor represents a significant conceptual shift from the "quick and easy" approach most pre-Abstract Model Dublin Core implementation enjoys. The effects of this shift on Dublin Core usage in libraries remain to be seen.

What Can Be Done With It

Many digital content management systems, such as DSpace and CONTENTdm, provide Qualified Dublin Core templates for describing digital materials put into these systems. Users would then come to this database and search or browse for content relevant to their needs.

Another very common use of Dublin Core is for OAI metadata harvesting. The OAI protocol requires that a simple Dublin Core record be present for every item represented in an OAI data provider, which can be supplemented with records in other formats. Requiring a common format establishes a baseline of interoperability among records from various data providers, although some robustness of searching may be lost by the use of this baseline common format. All libraries wishing to become OAI data providers must be able to produce simple Dublin Core for the records they wish to share via the protocol.

Examples

DSpace at MIT (uses Qualified Dublin Core)
Central Florida Memory (with CONTENTdm; uses Qualified Dublin Core)
Simple Dublin Core record served via OAI (Warning: this link retrieves raw XML!)

Who Should Be Using It

Most libraries, to some degree. Many libraries choose to use a metadata format more robust than Dublin Core for describing items in their local collections, then map this more robust metadata to Dublin Core for metadata harvesting, federated searching, or other means of cross-collection searching.

Related Technologies

More Information

DCMI Frequently Asked Questions
Using Dublin Core
An Introduction to Dublin Core from xml.com
Western States Dublin Core Metadata Best Practices
Caplan, Priscilla. Metadata Fundamentals for all Librarians. Chicago: American Library Association, 2003.