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.

Element	Qualifier	Definition
Title	alternative	Any form of the title used as a substitute or alternative to the formal title of the resource.
Description	tableOfContents	A list of subunits of the content of the resource.
	abstract	A summary of the content of the resource.
Date	created	Date of creation of the resource.
	valid	Date (often a range) of validity of a resource.
	available	Date (often a range) that the resource will become or did become available.
	issued	Date of formal issuance (e.g., publication) of the resource.
	modified	Date on which the resource was changed.
Format	extent	The size or duration of the resource.
	medium	The material or physical carrier of the resource.
Relation	isVersionOf	The 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.
	hasVersion	The described resource has a version, edition, or adaptation, namely, the referenced resource.
	isReplacedBy	The described resource is supplanted, displaced, or superceded by the referenced resource.
	replaces	The described resource supplants, displaces, or supersedes the referenced resource.
	isRequiredBy	The described resource is required by the referenced resource, either physically or logically.
	requires	The described resource requires the referenced resource to support its function, delivery, or coherence of content.
	isPartOf	The described resource is a physical or logical part of the referenced resource.
	hasPart	The described resource includes the referenced resource either physically or logically.
	isReferencedBy	The described resource is referenced, cited, or otherwise pointed to by the referenced resource.
	references	The described resource references, cites, or otherwise points to the referenced resource.
	isFormatOf	The described resource is the same intellectual content of the referenced resource, but presented in another format.
	hasFormat	The described resource pre-existed the referenced resource, which is essentially the same intellectual content presented in another format.
Coverage	spatial	Spatial characteristics of the intellectual content of the resoure.
	temporal	Temporal 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.

Element	Encoding Scheme	Definition
Subject	LCSH	Library of Congress Subject Headings
	MeSH	Medical Subject Headings
	DDC	Dewey Decimal Classification
	LCC	Library of Congress Classification
	UDC	UDC
Date	Period	DCMI period, a specification of the limits of a time interval.
	W3CDTF	W3C Encoding rules for dates and times - a profile based on ISO 8601
Resource Type	DCMIType	A list of types used to categorize the nature or genre of the content of the resource.
Format	IMT	The Internet media type of the resource.
Resource Identifier	URI	A Uniform Resource Identifier
Language	ISO639-2	ISO 639-2 codes for the representation of names of languages.
	RFC1766	Internet 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.
Relation	URI	A Uniform Resource Identifier
Spatial	Point	The DCMI Point identifies a point in space using its geographic coordinates.
	ISO3166	ISO 3166 Codes for the representation of names of countries
	Box	The DCMI Box identifies a region of space using its geographic limits.
	TGN	The Getty Thesaurus of Geographic Names
Temporal	period	A specification of the limits of a time interval.
	W3CDTF	W3C Encoding rules for dates and times - a profile based on ISO 8601

Conclusion

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.

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

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