Network Working Group S. Weibel
Request for Comments: 2413 OCLC Online Computer Library Center, Inc.
Category: Informational J. Kunze
University of California, San Francisco
C. Lagoze
Cornell University
M. Wolf
Reuters Limited
September 1998
Dublin Core Metadata for Resource Discovery
1. Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
2. Abstract
The Dublin Core Metadata Workshop Series began in 1995 with an
invitational workshop which brought together librarians, digital
library researchers, content eXPerts, and text-markup experts to
promote better discovery standards for electronic resources. The
Dublin Core is a 15-element set of descriptors that has emerged from
this effort in interdisciplinary and international consensus
building. This is the first of a set of Informational RFCs
describing the Dublin Core. Its purpose is to introdUCe the Dublin
Core and to describe the consensus reached on the semantics of each
of the 15 elements.
3. Introduction
Finding relevant information on the World Wide Web has become
increasingly problematic due to the explosive growth of networked
resources. Current Web indexing evolved rapidly to fill the demand
for resource discovery tools, but that indexing, while useful, is a
poor substitute for richer varieties of resource description.
An invitational workshop held in March of 1995 brought together
librarians, digital library researchers, and text-markup specialists
to address the problem of resource discovery for networked resources.
This activity evolved into a series of related workshops and
ancillary activities that have become known collectively as the
Dublin Core Metadata Workshop Series.
The goals that motivate the Dublin Core effort are:
- Simplicity of creation and maintenance
- Commonly understood semantics
- Conformance to existing and emerging standards
- International scope and applicability
- Extensibility
- Interoperability among collections and indexing systems
These requirements work at cross purposes to some degree, but all are
desirable goals. Much of the effort of the Workshop Series has been
directed at minimizing the tensions among these goals.
One of the primary deliverables of this effort is a set of elements
that are judged by the collective participants of these workshops to
be the core elements for cross-disciplinary resource discovery. The
term "Dublin Core" applies to this core of descriptive elements.
Early experience with Dublin Core deployment has made clear the need
to support qualification of elements for some applications. Thus, a
Dublin Core element may be expressed without qualification (as
described in this RFC) or with qualifiers that refine its semantics
(the subject of future RFCs). For the sake of interoperability,
simple indexing and discovery tools should be able to ignore any
qualifiers provided, while more advanced, semantically richer tools
should be able to use qualifiers to support more specialized or
precise discovery.
The broad agreements about syntax and semantics that have emerged
from the workshop series will be expressed in a series of
Informational RFCs, of which this document is the first.
4. Description of Dublin Core Elements
The following is the reference definition of the Dublin Core Metadata
Element Set. Further information about the Dublin Core Metadata
Element Set is available at [1]:
http://purl.org/metadata/dublin_core
In the element descriptions below, each element has a descriptive
name intended to convey a common semantic understanding of the
element, as well as a formal single-Word label intended to make the
syntactic specification of elements simpler for encoding schemes.
Although some environments, such as Html, are not case-sensitive, it
is recommended best practice always to adhere to the case conventions
in the element labels given below to avoid conflicts in the event
that the metadata is subsequently extracted or converted to a case-
sensitive environment, such as XML (Extensible Markup Language) [2].
Each element is optional and repeatable. Metadata elements may
appear in any order. The ordering of multiple occurrences of the
same element (e.g., Creator) may have a significance intended by the
provider, but ordering is not guaranteed to be preserved in every
system.
To promote global interoperability, a number of the element
descriptions suggest a controlled vocabulary for the respective
element values. It is assumed that other controlled vocabularies
will be developed for interoperability within certain local domains.
The metadata elements fall into three groups which roughly indicate
the class or scope of information stored in them: (1) elements
related mainly to the Content of the resource, (2) elements related
mainly to the resource when viewed as Intellectual Property, and (3)
elements related mainly to the Instantiation of the resource.
Content Intellectual Property Instantiation
----------- --------------------- -------------
Title Creator Date
Subject Publisher Format
Description Contributor Identifier
Type Rights Language
Source
Relation
Coverage
4.1. Title Label: "Title"
The name given to the resource, usually by the Creator or Publisher.
4.2. Author or Creator Label: "Creator"
The person or organization primarily responsible for creating the
intellectual content of the resource. For example, authors in the
case of written documents, artists, photographers, or illustrators in
the case of visual resources.
4.3. Subject and Keywords Label: "Subject"
The topic of the resource. Typically, subject will be expressed as
keywords or phrases that describe the subject or content of the
resource. The use of controlled vocabularies and formal
classification schemes is encouraged.
4.4. Description Label: "Description"
A textual description of the content of the resource, including
abstracts in the case of document-like objects or content
descriptions in the case of visual resources.
4.5. Publisher Label: "Publisher"
The entity responsible for making the resource available in its
present form, such as a publishing house, a university department, or
a corporate entity.
4.6. Other Contributor Label: "Contributor"
A person or organization not specified in a Creator element who has
made significant intellectual contributions to the resource but whose
contribution is secondary to any person or organization specified in
a Creator element (for example, editor, transcriber, and
illustrator).
4.7. Date Label: "Date"
A date associated with the creation or availability of the resource.
Recommended best practice is defined in a profile of ISO 8601 [3]
that includes (among others) dates of the forms YYYY and YYYY-MM-DD.
In this scheme, for example, the date 1994-11-05 corresponds to
November 5, 1994.
4.8. Resource Type Label: "Type"
The category of the resource, such as home page, novel, poem, working
paper, technical report, essay, dictionary. For the sake of
interoperability, Type should be selected from an enumerated list
that is currently under development in the workshop series.
4.9. Format Label: "Format"
The data format and, optionally, dimensions (e.g., size, duration) of
the resource. The format is used to identify the software and
possibly hardware that might be needed to display or operate the
resource. For the sake of interoperability, the format should be
selected from an enumerated list that is currently under development
in the workshop series.
4.10. Resource Identifier Label: "Identifier"
A string or number used to uniquely identify the resource. Examples
for networked resources include URLs and URNs (when implemented).
Other globally-unique identifiers, such as International Standard
Book Numbers (ISBN) or other formal names are also candidates for
this element.
4.11. Source Label: "Source"
Information about a second resource from which the present resource
is derived. While it is generally recommended that elements contain
information about the present resource only, this element may contain
metadata for the second resource when it is considered important for
discovery of the present resource.
4.12. Language Label: "Language"
The language of the intellectual content of the resource.
Recommended best practice is defined in RFC1766 [4].
4.13. Relation Label: "Relation"
An identifier of a second resource and its relationship to the
present resource. This element is used to express linkages among
related resources. For the sake of interoperability, relationships
should be selected from an enumerated list that is currently under
development in the workshop series.
4.14. Coverage Label: "Coverage"
The spatial or temporal characteristics of the intellectual content
of the resource. Spatial coverage refers to a physical region (e.g.,
celestial sector) using place names or coordinates (e.g., longitude
and latitude). Temporal coverage refers to what the resource is
about rather than when it was created or made available (the latter
belonging in the Date element). Temporal coverage is typically
specified using named time periods (e.g., neolithic) or the same
date/time format [3] as recommended for the Date element.
4.15. Rights Management Label: "Rights"
A rights management statement, an identifier that links to a rights
management statement, or an identifier that links to a service
providing information about rights management for the resource.
5. Security Considerations
The Dublin Core element set poses no risk to computers and networks.
It poses minimal risk to searchers who oBTain incorrect or private
information due to careless mapping from rich data descriptions to
the simple Dublin Core scheme. No other security concerns are likely
to be raised by the element description consensus documented here.
6. References
[1] Further information about the Dublin Core Metadata Element Set,
http://purl.org/metadata/dublin_core
[2] Extensible Markup Language (XML), http://www.w3.org/TR/REC-xml
[3] Date and Time Formats (based on ISO 8601), W3C Technical Note,
http://www.w3.org/TR/NOTE-datetime
[4] Alvestrand, H., "Tags for the Identification of Languages", RFC
1766, March 1995.
7. Authors' Addresses
Stuart L. Weibel
OCLC Online Computer Library Center, Inc.
Office of Research
6565 Frantz Rd.
Dublin, Ohio, 43017, USA
Phone: +1 614-764-6081
Fax: +1 614-764-2344
EMail: weibel@oclc.org
John A. Kunze
Center for Knowledge Management
University of California, San Francisco
530 Parnassus Ave, Box 0840
San Francisco, CA 94143-0840, USA
Phone: +1 510-525-8575
Fax: +1 415-476-4653
EMail: jak@ckm.ucsf.edu
Carl Lagoze
University Library and Department of Computer Science
Cornell University
Ithaca, NY 14853, USA
Phone: +1 607-255-6046
Fax: +1 607-255-4428
EMail: lagoze@cs.cornell.edu
Misha Wolf
Reuters Limited
85 Fleet Street
London EC4P 4AJ, UK
Phone: +44 171-542-6722
Fax: +44 171-542-8314
EMail: misha.wolf@reuters.com
8. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
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