Dublin Core
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The Dublin Core metadata element set is a standard ([NISO Standard Z39.85-2001]) for cross-domain information resource description. In other words, it provides a simple and standardised set of conventions for describing things online in ways that make them easier to find. Dublin Core is widely used to describe digital materials such as video, sound, image, text and composite media like web pages. Implementations of Dublin Core are typically XML and Resource Description Framework based.
The term "Dublin Core" has no connection with Dublin, Ireland; rather, it is a basic but expandable "core" list of descriptors that were developed with the support of OCLC, a library consortium which is based in Dublin, Ohio, USA. The semantics of Dublin Core were established and are maintained by an international, cross-disciplinary group of professionals from librarianship, computer science, text encoding, the museum community, and other related fields of scholarship and practice.
The Dublin Core Metadata Initiative ([DCMI]) is an organization providing an open forum for the development of interoperable online metadata standards that support a broad range of purposes and business models. DCMI's activities include consensus-driven working groups, global conferences and workshops, standards liaison, and educational efforts to promote widespread acceptance of metadata standards and practices.
The Dublin Core standard includes two levels: Simple and Qualified. Simple Dublin Core comprises fifteen elements; Qualified Dublin Core includes three additional elements (Audience, Provenance and RightsHolder), as well as a group of element refinements (also called qualifiers) that refine the semantics of the elements in ways that may be useful in resource discovery.
Simple Dublin Core
The Simple Dublin Core Metadata Element Set (DCMES) consists of 15 metadata elements:
- Title
- Creator
- Subject
- Description
- Publisher
- Contributor
- Date
- Type
- Format
- Identifier
- Source
- Language
- Relation
- Coverage
- Rights
Full information on element definitions and term relationships can be found in the Dublin Core Metadata Registry [Dublin Core Metadata Registry].
Qualified Dublin Core
Subsequent to the specification of the original 15 elements, an ongoing process to develop exemplary terms extending or refining the Dublin Core Metadata Element Set (DCMES) was begun. The additional terms were identified, generally in working groups of the Dublin Core Metadata Initiative, and judged by the DCMI Usage Board to be in conformance with principles of good practice for the qualification of Dublin Core metadata elements.
Element refinements make the meaning of an element narrower or more specific. A refined element shares the meaning of the unqualified element, but with a more restricted scope. The guiding principle for the qualification of Dublin Core elements, colloquially known as the Dumb-Down Principle [link], states that an application that does not understand a specific element refinement term should be able to ignore the qualifier and treat the metadata value as if it were an unqualified (broader) element. While this may result in some loss of specificity, the remaining element value (without the qualifier) should continue to be generally correct and useful for discovery.
In addition to element refinements, Qualified Dublin Core includes a set of recommended encoding schemes, designed to aid in the interpretation of an element value. These schemes include controlled vocabularies and formal notations or parsing rules. A value expressed using an encoding scheme may thus be a token selected from a controlled vocabulary (e.g., a term from a classification system or set of subject headings) or a string formatted in accordance with a formal notation (e.g., "2000-12-31" as the standard expression of a date). If an encoding scheme is not understood by an application, the value may still be useful to a human reader.
DCMI also maintains a small, general vocabulary recommended for use within the element Type. This vocabulary currently consists of 12 terms :
- Collection
- Dataset
- Event
- Image
- InteractiveResource
- MovingImage
- PhysicalObject
- Service
- Software
- Sound
- StillImage
- Text
Dublin Core Syntaxes
Syntax choices for DC metadata depend on a number of variables, and "one size fits all" prescriptions rarely apply. When considering an appropriate syntax, it is important to note that Dublin Core concepts and semantics are designed to be syntax independent, are equally applicable in a variety of contexts, as long as the metadata is in a form suitable for interpretation both by machines and by human beings.
The Dublin Core Abstract Model [Dublin Core Abstract Model] provides a reference model against which particular DC encoding guidelines can be compared, independent of any particular encoding syntax. Such a reference model allows implementors to gain a better understanding of the kinds of descriptions they are trying to encode and facilitates the development of better mappings and translations between different syntaxes.
Application Examples
One Document Type Definition based on Dublin Core is the [Open Source Metadata Framework] (OMF) specification. OMF is in turn used by ScrollKeeper, which is used by the GNOME desktop and KDE help browsers and the ScrollServer documentation server. PBCore is also based on Dublin Core. The Zope CMF's Metadata products, used by the Plone and the Nuxeo CPS Content management systems, also implement Dublin Core.
DCMI also maintains a list of projects using Dublin Core on its website.
See also
References
External links
- [“Using Dublin Core” –the official usage guide]
- [Dublin Core Metadata Initiative]
- [Dublin Core Metadata Initiative Publishes DCMI Abstract Model] (Cover Pages, March 2005)
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