Dublin Core
From Free net encyclopedia
The Dublin Core metadata standard is a simple yet effective element set for describing a wide range of networked resources. 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. The semantics of Dublin Core have been established 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.
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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
Each Dublin Core element is optional and may be repeated. The Dublin Core Metadata Initiative (DCMI) has established standard ways to refine elements and encourage the use of encoding and vocabulary schemes. There is no prescribed order in Dublin Core for presenting or using the elements.
Full information on element definitions and term relationships can be found in the Dublin Core Metadata Registry (see References).
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," 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 will 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., "2000-01-01" 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, consisting of 12 terms, can be found on the DCMI webpage or the Dublin Core Metadata Registry (see References).
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 (see References) 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
- Dublin Core Metadata Initiative
- “Using Dublin Core” –the official usage guide
- Dublin Core Metadata Registry
- Dublin Core Abstract Model
- Dublin Core Metadata Initiative Publishes DCMI Abstract Model (Cover Pages, March 2005)cs:Dublin Core
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