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rfc:rfc2413

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.

Weibel, et. al. Informational [Page 1] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

 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:
  1. Simplicity of creation and maintenance
  2. Commonly understood semantics
  3. Conformance to existing and emerging standards
  4. International scope and applicability
  5. Extensibility
  6. 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.

Weibel, et. al. Informational [Page 2] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

 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.

Weibel, et. al. Informational [Page 3] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

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

Weibel, et. al. Informational [Page 4] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

 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 RFC 1766 [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.

Weibel, et. al. Informational [Page 5] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

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

Weibel, et. al. Informational [Page 6] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

 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

Weibel, et. al. Informational [Page 7] RFC 2413 Dublin Core Metadata for Resource Discovery September 1998

8. Full Copyright Statement

 Copyright (C) The Internet Society (1998).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Weibel, et. al. Informational [Page 8]

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