Dublin Core Metadata for Resource Discovery

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 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.

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

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