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Versions: 00 01 02                                                      
Network Working Group                                    Martin Hamilton
INTERNET-DRAFT                                   Loughborough University
Expires January 1998                                     Renato Iannella
                                                            DSTC Pty Ltd
                                                              Jon Knight
                                                 Loughborough University
                                                               July 1997


       Representing the Dublin Core within X.500, LDAP and CLDAP

                  Filename: draft-hamilton-dcxl-02.txt


                          Status of this Memo

      This document is an Internet-Draft.  Internet-Drafts are working
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Abstract

   The Dublin Core is a simple resource description format which arose
   out of a loose grouping of "librarians, archivists, humanities
   scholars and geographers, as well as standards makers in the
   Internet, Z39.50 and Standard Generalized Markup Language (SGML)
   communities" [1].

   This document describes a mapping from the abstract model of the
   Dublin Core to the X.500 [2], LDAP [3], and CLDAP [4] directory
   service protocols.





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1. The Dublin Core in X.500, LDAP and CLDAP

   We propose that each of the fifteen elements of the Dublin Core be
   made into an X.500/[C]LDAP attribute, and that these attributes be
   gathered together in an object class:

      Name:             dcObject
      Description:      object containing the Dublin Core attributes
      OID:              lutObjectClass.1 (1.3.6.1.4.1.1828.2.1)
      SubclassOf:       top
      MustContain:
      MayContain:       dcTitle, dcCreator, dcSubject, dcDescription,
                          dcPublisher, dcContributors, dcDate,
                          dcType, dcFormat, dcIdentifer, dcSource,
                          dcLanguage, dcRelation, dcCoverage, dcRights

   Attribute definitions for the individual Dublin Core elements:

      Name:             dcTitle
      Description:      The name of the resource
      OID:              lutAttributeType.1 (1.3.6.1.4.1.1828.1.1)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcCreator
      Description:      The person(s) primarily responsible for the
                          intellectual content of the resource
      OID:              lutAttributeType.2 (1.3.6.1.4.1.1828.1.2)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcSubject
      Description:      The topic addressed by the resource, or a
                          set of appropriate keywords
      OID:              lutAttributeType.3 (1.3.6.1.4.1.1828.1.3)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcDescription
      Description:      A plain text description or abstract about
                          the resource.
      OID:              lutAttributeType.4 (1.3.6.1.4.1.1828.1.4)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False



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      Name:             dcPublisher
      Description:      The agent or agency responsible for making the
                          resource available
      OID:              lutAttributeType.5 (1.3.6.1.4.1.1828.1.5)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcContributors
      Description:      The person(s), such as editors and transcribers, who
                          have made other significant intellectual
                          contributions to the work
      OID:              lutAttributeType.6 (1.3.6.1.4.1.1828.1.6)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcDate
      Description:      The date of publication
      OID:              lutAttributeType.7 (1.3.6.1.4.1.1828.1.7)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcType
      Description:      The genre of the resource, such as novel, poem, or
                          dictionary
      OID:              lutAttributeType.8 (1.3.6.1.4.1.1828.1.8)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcFormat
      Description:      The physical manifestation of the resource, such as
                          Postscript file or Windows executable file
      OID:              lutAttributeType.9 (1.3.6.1.4.1.1828.1.9)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcIdentifier
      Description:      String or number used to uniquely identify the
                          resource
      OID:              lutAttributeType.10 (1.3.6.1.4.1.1828.1.10)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False




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      Name:             dcSource
      Description:      Resources, either print or electronic, from which
                          this resource is derived, if applicable
      OID:              lutAttributeType.11 (1.3.6.1.4.1.1828.1.11)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcLanguage
      Description:      Language of the intellectual content
      OID:              lutAttributeType.12 (1.3.6.1.4.1.1828.1.12)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcRelation
      Description:      Relationship to other resources
      OID:              lutAttributeType.13 (1.3.6.1.4.1.1828.1.13)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcCoverage
      Description:      The spatial locations and temporal durations
                          characteristic of the resource
      OID:              lutAttributeType.14 (1.3.6.1.4.1.1828.1.14)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

      Name:             dcRights
      Description:      Information concerning the intellectual property
                          rights that are being exercised over the
                          resource (including access terms)
      OID:              lutAttributeType.15 (1.3.6.1.4.1.1828.1.15)
      Syntax:           DirectoryString
      SizeRestriction:  None
      SingleValued:     False

2. Examples and implementation considerations

   For example, using Quipu [5] EDB notation, a Dublin Core "Title"
   element which had the value "Cities of The Red Night" would be
   represented as the attribute/value pair:

     dcTitle= Cities of The Red Night

   One aspect of the Dublin Core does not translate directly to X.500



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   and LDAP - each element may have additional qualifying information
   attached to it.  This gives the creator of the record a way of
   indicating additional semantics, e.g. the classification scheme being
   used in the "Subject" element.

   Since X.500 and LDAP are, like most Internet based search and
   retrieval protocols, attribute/value oriented, it is necessary to
   find a place to put this extra information.  We propose that, given
   the difficulty of incorporating this model within the X.500/LDAP
   paradigm, a simple but sub-optimal approach be taken - with any
   qualifying information being placed at the beginning of the value
   part of the attribute/value pair, delimited using round brackets, and
   with any additional qualifiers following using comma separation.

   For example, if the subject classification for the above book were
   813 in the Dewey Decimal system, the resulting Dublin Core record
   expressed as an X.500 EDB entry would look like this:

     dcSubject= (scheme=DDC) 813

3. Extensibility

   It is important to note that the Dublin Core element set is intended
   for use in describing document-like objects, and not as a means of
   describing arbitrary objects.  Furthermore, the number of elements is
   strictly limited in the interests of interoperability.

   Work is ongoing on the Warwick Framework [6], which attempts to
   provide a mechanism for packaging together collections of descriptive
   information.  It is envisaged that this would be used in cases where
   the Dublin Core element set did not provide enough descriptive
   capability.  This is a subject for further study.

4. Security considerations

   This proposal does not introduce any new security related issues.

   One of the main uses to which the Dublin Core is expected to be put
   is in the generation of author supplied cataloguing information for
   on-line resources.  Implementations which manipulate externally
   produced data should treat it with caution - for example, to avoid
   buffer overrun problems and unexpected evaluation of metacharacters.

5. Conclusions

   This document has shown how the X.500 protocol, and the related LDAP
   and CLDAP protocols, may be used as carriers for the abstract
   resource descriptions of the Dublin Core proposal.



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   It should be apparent that a little care is necessary when delivering
   this information via these protocols, but that this does not imply
   any great additional implementation complexity.

6. Acknowledgements

   Thanks to Hoylen Sue, CiTR Pty Ltd (Australia), Rachel Heery and
   Lorcan Dempsey for their comments on draft versions of this document.

   This work was supported by UK Electronic Libraries Programme (eLib)
   grant 12/39/01, the European Commission's Telematics for Research
   Programme, grant RE 1004, and the Cooperative Research Centres
   Program, through the Department of the Prime Minister and Cabinet of
   Australia.

7. References


     [1]         S. Weibel.  "Metadata: The Foundations of Resource
                 Description", D-Lib Magazine, July 1995.
                 <URL:http://www.ukoln.ac.uk/dlib/dlib/July95/07weibel.html>
                 <URL:http://www.dlib.org/dlib/July95/07weibel.html>


     [2]         C. Weider, J. Reynolds, S. Heker.  "Technical Overview
                 of Directory Services Using the X.500 Protocol", RFC
                 1309.  March 1992.
                 <URL:ftp://ftp.internic.net/rfc/rfc1309.txt>


     [3]         W. Yeong, T. Howes & S.  Kille.  "Lightweight Directory
                 Access Protocol", RFC 1777.  March 1995.
                 <URL:ftp://ftp.internic.net/rfc/rfc1777.txt>


     [4]         A. Young.  "Connection-less Lightweight Directory
                 Access Protocol", RFC 1798.  June 1995.
                 <URL:ftp://ftp.internic.net/rfc/rfc1798.txt>


     [5]         S.E. Kille.  "Implementing X.400 and X.500: the PP and
                 QUIPU systems", Artech House, 1991.


     [6]         L. Dempsey, S. Weibel.  "The Warwick Metadata Workshop:
                 A Framework for the Deployment of Resource Descrip-
                 tion", D-Lib Magazine, July/August 1996.
                 <URL:http://www.ukoln.ac.uk/dlib/dlib/july96/07weibel.html>



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                 <URL:http://www.dlib.org/dlib/july96/07weibel.html>


8. Authors' addresses

   Martin Hamilton
   Department of Computer Studies
   Loughborough University of Technology
   Leics. LE11 3TU, UK

   Email: m.t.hamilton@lut.ac.uk


   Renato Iannella
   Research Data Network CRC
   DSTC Pty Ltd
   Gehrmann Laboratories
   University of Queensland
   Australia

   Email:  renato@dstc.edu.au


   Jon Knight
   Department of Computer Studies
   Loughborough University of Technology
   Leics. LE11 3TU, UK

   Email: j.p.knight@lut.ac.uk






















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