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Created: March 21, 2005.
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Dublin Core Metadata Initiative Publishes DCMI Abstract Model.

In March 2005 the DCMI Directorate announced the release of the DCMI Abstract Model specification as a DCMI Recommendation. DCMI recommendations are semantic or technical specifications that have progressed through the formal review and approval process of the Dublin Core Metadata Initiative; these specifications are stable and are supported for adoption by the Dublin Core community.

DCMI is formed around a community of individuals and organizations "committed to building and developing metadata standards, practices, policies and technologies. The organization is dedicated to promoting the widespread adoption of interoperable metadata standards and developing specialized metadata vocabularies for describing resources that enable more intelligent information discovery systems."

The approved DCMI Abstract Model is a foundational document that "specifies an abstract model for Dublin Core Metadata Initiative metadata. The primary purpose of the specification is to provide a reference model against which particular Dublin Core encoding guidelines can be compared. To function well, a reference model needs to be independent of any particular encoding syntax. Such a reference model allows us to gain a better understanding of the kinds of descriptions that we are trying to encode and facilitates the development of better mappings and translations between different syntaxes."

The DCMI Abstract Model is "primarily aimed at the developers of software applications that support Dublin Core metadata, people involved in developing new syntax encoding guidelines for Dublin Core metadata, and those people developing metadata application profiles based on the Dublin Core."

The DCMI abstract model as represented in the UML diagram, definitions, and prose assertions defines both DCMI metadata descriptions and resources being described by DCMI metadata descriptions. For example, in the DCML resource model: (1) "Each resource has zero or more property/value pairs; (2) Each property/value pair is made up of one property and one value; (3) Each value is a resource — the physical or conceptual entity that is associated with a property when it is used to describe a resource;" etc. In the DCMI description model: (1) A description is made up of one or more statements (about one, and only one, resource) and zero or one resource URI (a URI reference that identifies the resource being described); (2) Each statement instantiates a property/value pair and is made up of a property URI (a URI reference that identifies a property), zero or one value URI (a URI reference that identifies a value of the property), zero or one vocabulary encoding scheme URI (a URI reference that identifies the class of the value) and zero or more value representations of the value; (3) The value representation may take the form of a value string or a rich representation..."

The abstract model "indicates that each DCMI metadata description describes one, and only one, resource; this is commonly referred to as the one-to-one principle. However, real-world metadata applications tend to be based on loosely grouped sets of descriptions, where the described resources are typically related in some way, known here as description sets. A description set is a set of one or more descriptions about one or more resources. For example, a description set might comprise descriptions of both a painting and the artist. Furthermore, it is often the case that a description set will also contain a description about the description set itself — sometimes referred to as 'admin metadata' or 'meta-metadata'. Description sets are instantiated, for the purposes of exchange between software applications, in the form of metadata records, according to one of the DCMI encoding guidelines (XHTML meta tags, XML, RDF/XML, etc.)."

The specification document contains four appendices. Appendix A is a note about structured values, and discusses 'structured values' (labelled strings, unlabeled strings, marked-up text, related resource descriptions) as they are commonly used in DC metadata applications. Each of these types of structured values is mapped to concepts in the DCMI Abstract Model. Appendix B discusses the relationship between the DCMI abstract model and the Resource Description Framework (RDF), since "RDF currently provides DCMI with the richest encoding environment of the available encoding syntaxes."

Appendix C in the DCMI Abstract Model specification compares the DCMI abstract model with the Guidelines for Implementing Dublin Core in XML DCMI Recommendation. Some aspects of the DCMI abstract model are supported by the Guidelines document (properties property URIs, value strings, value string languages, encoding schemes, encoding scheme URIs, resource classes) while others are not (resource URIs, value URIs, rich representations, related descriptions, property/sub-property relationships, resource class URIs).

Appendix D compares the DCMI abstract model with the DCMI Recommendation Expressing Dublin Core in HTML/XHTML 'meta' and 'link' elements.

Bibliographic Information

DCMI Abstract Model. Copyright (c) 1995-2005 DCMI. Approved as a DCMI Recommendation. Metadata associated with the DCMI Abstract Model. By Andy Powell (UKOLN, University of Bath, UK), Mikael Nilsson (KMR Group, CID, NADA, KTH - Royal Institute of Technology, Sweden Ambjörn Naeve (KMR Group, CID, NADA, KTH - Royal Institute of Technology, Sweden), and Pete Johnston (UKOLN, University of Bath, UK). Date Issued: 2005-03-07. Version URI: Latest Version URL:

Document appendices: Appendix A: A note about structured values; Appendix B: The abstract model and RDF; Appendix C: The abstract model and XML; Appendix D: The abstract model and XHTML.

About Dublin Core

The mission of of DCMI is to make it easier to find resources using the Internet through the following activities: (1) Developing metadata standards for discovery across domains, (2) Defining frameworks for the interoperation of metadata sets, and (3) Facilitating the development of community- or disciplinary-specific metadata sets that are consistent with [its other goals]. DCMI supports standards development and maintenance, [with activities] such as organizing international workshops and working group meetings directed toward developing and maintaining DCMI recommendations. It provides tools, services, and infrastructure, including the DCMI metadata registry to support the management and maintenance of DCMI metadata in multiple languages. DCMI provides educational outreach and community liaison, including developing and distributing educational and training resources, consulting, and coordinating activities within and between other metadata communities..."

The DCMI Registry Working Group has implemented an open-source Metadata Registry, "designed to promote the discovery and reuse of exiting metadata definitions. It provides users, and applications, with an authoritative source of information about the Dublin Core element set and related vocabularies. This simplifies the discovery of terms and related definitions, and illustrates the relationship between terms. In 2004-07-29, Version 3.3.0 of the DCMI Metadata Registry has been released; this release includes new functionality and a new user interface. The item detail screen now includes a quick-link to an RDF/XML, N-TRIPLE and N3 views of the data... The reuse of existing metadata terms is essential to standardization, and promotes greater interoperability between metadata element sets. The discovery of existing terms is an essential, and prerequisite, step in this process. The Registry application promotes the wider adoption, standardization and interoperability of metadata by facilitating its discovery, and reuse, across diverse disciplines and communities of practice..."

Since the "OCLC/NCSA Metadata Workshop that took place in Dublin, Ohio, 1-3 March 1995, the Dublin Core community has grown from the 52 original workshop participants to an international community of researchers and practitioners from more than 50 countries.

DCMI is open: anyone can participate, use the standard, and support its evolution. Anyone wishing to participate may do so by simply joining the appropriate mailing list for the working group activity of interest. DCMI is also international: there are 25 languages in the DCMI metadata registry. DCMI is independent — no industry or government agency controls the DCMI agenda. We are a grass roots global collaboration with many national standards and an ISO standard in our portfolio of value..." [adapted from News and About]

As of 2005-03, DCMI had nineteen (19) active Working Groups: Accessibility Working Group; Agents Working Group; Architecture Working Group; Citation Working Group; Collection Description Working Group; Date Working Group; DC-Kernel/ERC Working Group; Education Working Group; Environment Working Group; Global Corporate Circle; Government Working Group; Libraries Working Group; Localization and Internationalization Working Group; Persistent Identifier Working Group; Preservation Working Group; Registry Working Group; Standards Working Group; Tools Working Group; User Documentation Working Group.

About DC-2005: "Metadata Vocabularies in Practice"

DC-2005 will be held 12-15 September 2005 as the fifth in a series of DCMI conferences. It is hosted by the University Carlos III of Madrid, Leganes, Madrid, Spain.

"Conference attendees will examine the practicalities of maintaining and using controlled sets of terms (vocabularies) in the context of the Web. DC-2005 aims at bringing together several distinct communities of vocabulary users:

  • Users of metadata standards such as Dublin Core and Learning Object Metadata (LOM), with their sets of descriptive "elements" and "properties"
  • The W3C Semantic Web Activity, which has formalized the notion of ontologies
  • Users of Knowledge Organization Systems, which encompass value-space structures such as "thesauri" and "subject classifications"
  • The world of corporate intranets, which use "taxonomies"

Topics of particular relevance include:publication of vocabularies as formal schemas; community processes of vocabulary development; vocabulary maintenance and workflows; corporate enterprise metadata and taxonomies; formal ontologies and Semantic Web frameworks; application profiles and vocabulary adaptations; metadata normalization and crosswalks; versioning of vocabularies; use of term identifiers and dereferencing practice; vocabulary registries and registry services; multilingual vocabularies and translations; vocabularies and accessibility..."

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