The Dublin Core metadata terms are a set of vocabulary terms which can be used to describe resources for the purposes of discovery. The terms can be used to describe a full range of web resources (video, images, web pages, etc.), physical resources such as books and objects like artworks. The full set of Dublin Core metadata terms can be found on the Dublin Core Metadata Initiative (DCMI) website. The original set of 15 classic  metadata terms, known as the Dublin Core Metadata Element Set  are endorsed in the following standards documents:
Dublin Core Metadata can be used for multiple purposes, from simple resource description, to combining metadata vocabularies of different metadata standards, to providing interoperability for metadata vocabularies in the Linked data cloud and Semantic web implementations.
"Dublin" refers to Dublin, Ohio, USA where the work originated during the 1995 invitational OCLC/NCSA Metadata Workshop, hosted in by Online Computer Library Center (OCLC), a library consortium based there, and the National Center for Supercomputing Applications (NCSA). "Core" refers to the metadata terms as "broad and generic being usable for describing a wide range of resources." The semantics of Dublin Core were established and are maintained by an international, cross-disciplinary group of professionals from librarianship, computer science, text encoding, museums, and other related fields of scholarship and practice.
The Dublin Core Metadata Initiative (http://dublincore.org/ DCMI) provides an open forum for the development of interoperable online metadata standards for a broad range of purposes and of 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. In 2008, DCMI separated from OCLC and incorporated as an independent entity.
Levels of the standard 
The Dublin Core standard includes two levels: Simple and Qualified. Simple Dublin Core comprises 15 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:
Each Dublin Core element is optional and may be repeated. The 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. The Dublin Core became ISO 15836 standard in 2006 and is used as a base-level data element set for the description of learning resources in the ISO/IEC 19788-2 Metadata for learning resources (MLR) -- Part 2: Dublin Core elements, prepared by the ISO/IEC JTC1 SC36.
Full information on element definitions and term relationships can be found in the Dublin Core Metadata Registry.
Example of code 
<meta name="DC.Publisher" content="publisher-name" >
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.
Elements 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 may thus be a token selected from a controlled vocabulary (for example, a term from a classification system or set of subject headings) or a string formatted in accordance with a formal notation, for example, "2000-12-31" as the ISO standard expression of a date. If an encoding scheme is not understood by an application, the value may still be useful to human reader.
Audience, Provenance and RightsHolder are elements, but not part of the Simple Dublin Core 15 elements. Use Audience, Provenance and RightsHolder only when using Qualified Dublin Core. DCMI also maintains a small, general vocabulary recommended for use within the element Type. This vocabulary currently consists of 12 terms.
Syntax choices for Dublin Core 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 provides a reference model against which particular Dublin Core encoding guidelines can be compared, independent of any particular encoding syntax. Such a reference model allows implementers 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.
Some applications 
One Document Type Definition based on Dublin Core is the Open Source Metadata Framework (OMF) specification. OMF is in turn used by Rarian (superseding 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, ERP5, the Nuxeo CPS Content management systems, SimpleDL, and FedoraCommons also implement Dublin Core.
DCMI also maintains a list of projects using Dublin Core on its website.
See also 
- Metadata registry
- Metadata Object Description Schema
- Metadata from Wikiversity
- Semantic Web
- Ontology (information science)
- Open Archives Initiative
- Controlled vocabulary
- METS, a metadata standard maintained by the Library of Congress for the Digital Library Federation
- Preservation Metadata: Implementation Strategies (PREMIS)
Related Software 
- Dublin Core Meta Toolkit (Conversion of Access, MySQL, or CSV data to DublinCore metadata)
- Fedora repository architecture and Project (An open-source software system capable of implementing OAI-PMH (and thus Dublin Core).
- Omeka, A free, open-source, unqualified Dublin-Core compliant web-publishing system for digital archives.
- The Archivist's Toolkit is a self-described as an "Archival Data Management system" able to work with the Dublin Core format. It will soon be merged with Archon, which is ambiguous as to its OAI support.
- ICA-AtoM, a web-based archival description/publication software that can serve as an OAI-PMH repository and uses OAI-PMH as the main language for remote data exchange
- "DCMI Metadata Terms". Dublincore.org. Retrieved 2013-04-05.
- "DCMI Metadata Terms". Dublincore.org. Retrieved 2013-04-05.
- "DCMI Specifications". Dublincore.org. 2009-12-14. Retrieved 2013-04-05.
- "Dublin Core Metadata Element Set, Version 1.1". Dublincore.org. Retrieved 2013-04-05.
- The Dublin Core Metadata Element Set, Dublin Core Metadata Initiative, August 2007
- "ISO 15836:2009 - Information and documentation - The Dublin Core metadata element set". Iso.org. 2009-02-18. Retrieved 2013-04-05.
- "NISO Standards - National Information Standards Organization". Niso.org. 2007-05-22. Retrieved 2013-04-05.
- "OCLC Research and the Dublin Core Metadata Initiative". Retrieved 21 April 2010.
- Dublin Core Metadata Registry
- "WebCite® archive form". WebCite. "Metadata (optional) These are Dublin Core elements. [...]"
- Dumb-Down Principle for qualifiers
- Dublin Core Abstract Model
- "DCMI Projects - Alphabetical". DCMI. Retrieved 2013-03-15.
Further reading 
- Harvey, Ross; Philip Hider (2004). Organising Knowledge in a Global Society. Wagga Wagga NSW: Charles Sturt University. ISBN 1-876938-66-8.
- "Lecture slides about Dublin Core", by Professor Luca Dini, lecturer at the Free University of Bolzano
- Dublin Core Metadata Initiative
- Dublin Core usage guide
- Dublin Core Metadata Initiative Publishes DCMI Abstract Model (Cover Pages, March 2005)
- Metadata Object Description Schema (MODS)
- The Dublin Core Generator: A tool for generating Dublin Core code