Dublin Core - Tagging the Web for better search and retrieval (3/3) - exploring XML | WebReference

Dublin Core - Tagging the Web for better search and retrieval (3/3) - exploring XML

Dublin Core - Tagging the Web for better search and retrieval

Dublin Core Qualifiers

Qualifiers are used for element refinement. These qualifiers 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. A client 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. The definitions of element refinement terms for qualifiers must be publicly available.

TitlealternativeAny form of the title used as a substitute or alternative to the formal title of the resource.
DescriptiontableOfContentsA list of subunits of the content of the resource.
abstractA summary of the content of the resource.
DatecreatedDate of creation of the resource.
validDate (often a range) of validity of a resource.
availableDate (often a range) that the resource will become or did become available.
issuedDate of formal issuance (e.g., publication) of the resource.
modifiedDate on which the resource was changed.
FormatextentThe size or duration of the resource.
mediumThe material or physical carrier of the resource.
RelationisVersionOfThe described resource is a version, edition, or adaptation of the referenced resource. Changes in version imply substantive changes in content rather than differences in format.
hasVersionThe described resource has a version, edition, or adaptation, namely, the referenced resource.
isReplacedByThe described resource is supplanted, displaced, or superceded by the referenced resource.
replacesThe described resource supplants, displaces, or supersedes the referenced resource.
isRequiredByThe described resource is required by the referenced resource, either physically or logically.
requiresThe described resource requires the referenced resource to support its function, delivery, or coherence of content.
isPartOfThe described resource is a physical or logical part of the referenced resource.
hasPartThe described resource includes the referenced resource either physically or logically.
isReferencedByThe described resource is referenced, cited, or otherwise pointed to by the referenced resource.
referencesThe described resource references, cites, or otherwise points to the referenced resource.
isFormatOfThe described resource is the same intellectual content of the referenced resource, but presented in another format.
hasFormatThe described resource pre-existed the referenced resource, which is essentially the same intellectual content presented in another format.
CoveragespatialSpatial characteristics of the intellectual content of the resoure.
temporalTemporal characteristics of the intellectual content of the resource.

Encoding Schemes

These qualifiers identify schemes that 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 a client or agent, the value may still be useful to a human reader. The definitive description of an encoding scheme for qualifiers must be clearly identified and available for public use.

ElementEncoding SchemeDefinition
SubjectLCSHLibrary of Congress Subject Headings
MeSHMedical Subject Headings
DDCDewey Decimal Classification
LCCLibrary of Congress Classification
DatePeriodDCMI period, a specification of the limits of a time interval.
W3CDTFW3C Encoding rules for dates and times - a profile based on ISO 8601
Resource TypeDCMITypeA list of types used to categorize the nature or genre of the content of the resource.
FormatIMTThe Internet media type of the resource.
Resource IdentifierURIA Uniform Resource Identifier
LanguageISO639-2ISO 639-2 codes for the representation of names of languages.
RFC1766Internet RFC 1766 'Tags for the identification of Language' specifies a two letter code taken from ISO 639, followed optionally by a two letter country code taken from ISO 3166.
RelationURIA Uniform Resource Identifier
SpatialPointThe DCMI Point identifies a point in space using its geographic coordinates.
ISO3166ISO 3166 Codes for the representation of names of countries
BoxThe DCMI Box identifies a region of space using its geographic limits.
TGNThe Getty Thesaurus of Geographic Names
TemporalperiodA specification of the limits of a time interval.
W3CDTFW3C Encoding rules for dates and times - a profile based on ISO 8601


The fifteen Dublin Core elements are a limited list of nouns, while the DC qualifiers provide a rich, yet standardized and restricted set of adjectives for qualifying resources.

When you roll out a meta data initiative on your Web site, you might want to consider these elements for your meta tags, rather than inventing your own. Use them in your XML vocabularies and include them using namespaces rather than defining a set of equivalent but different tags. The search engines of the world will reward you with better, more accurate indexing.


Produced by Michael Claßen
All Rights Reserved. Legal Notices.

URL: http://www.webreference.com/xml/column23/3.html
Created: Nov 05, 2000
Revised: Nov 05, 2000