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Network Working Group C. Lynch Request for Comments: 2288 Coalition for Networked Information Category: Informational C. Preston

                                                      Preston & Lynch
                                                            R. Daniel
                                       Los Alamos National Laboratory
                                                        February 1998
              Using Existing Bibliographic Identifiers
                                 as
                       Uniform Resource Names

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.

Abstract

 A system for Uniform Resource Names (URNs) must be capable of
 supporting identifiers from existing widely-used naming systems.
 This document discusses how three major bibliographic identifiers
 (the ISBN, ISSN and SICI) can be supported within the URN framework
 and the currently proposed syntax for URNs.

1. Introduction

 The ongoing work of several IETF working groups, most recently in the
 Uniform Resource Names working group, has culminated the development
 of a syntax for Uniform Resource Names (URNs).   The functional
 requirements and overall framework for Uniform Resource Names are
 specified in RFC 1737 [Sollins & Masinter] and the specification for
 the URN syntax is RFC 2141 [Moats].
 As part of the validation process for the development of URNs the
 IETF working group has agreed that it is important to demonstrate
 that the current URN syntax proposal can accommodate existing
 identifiers from well established namespaces.  One such
 infrastructure for assigning and managing names comes from the
 bibliographic community.  Bibliographic identifiers function as names
 for objects that exist both in print and, increasingly, in electronic
 formats.  This memo demonstrates the feasibility of supporting three

Lynch, et. al. Informational [Page 1] RFC 2288 Bibligraphic Identifiers February 1998

 representative bibliographic identifiers within the currently
 proposed URN framework and syntax.
 Note that this document does not purport to define the "official"
 standard way of moving these bibliographic identifiers into URNs; it
 merely demonstrates feasibility.  It has not been developed in
 consultation with these standards bodies and maintenance agencies
 that oversee the existing bibliographic identifiers.  Any actual
 Internet standard for encoding these bibliographic identifiers as
 URNs will need to be developed in consultation with the responsible
 standards bodies and maintenance agencies.
 In addition, there are several open questions with regard to the
 management and registry of Namespace Identifiers (NIDs) for URNs.
 For purposes of illustration, we have used the three NIDs "ISBN",
 "ISSN" and "SICI" for the three corresponding bibliographic
 identifiers discussed in this document.  While we believe this to be
 the most appropriate choice, it is not the only one.  The NIDs could
 be based on the standards body and standard number (e.g.  "US-ANSI-
 NISO-Z39.56-1997" rather than "SICI").  Alternatively, one could lump
 all bibliographic identifiers into a single "BIBLIOGRAPHIC" name
 space, and structure the namespace-specific string to specify which
 identifier is being used.  Any final resolution of this must wait for
 the outcome of namespace management discussions in the working group
 and the broader IETF community.
 For the purposes of this document, we have selected three major
 bibliographic identifiers (national and international) to fit within
 the URN framework.  These are the International Standard Book Number
 (ISBN) [ISO1], the International Standard Serials Number (ISSN)
 [NISO1,ISO2, ISO3], and the Serial Item and Contribution Identifier
 (SICI) [NISO2].  An ISBN is used to identify a monograph (book).  An
 ISSN is used to identify serial publications (journals, newspapers)
 as a whole.   A SICI augments the ISSN in order to identify
 individual issues of serial publications, or components within those
 issues (such as an individual article, or the table of contents of a
 given issue).  The ISBN and ISSN are defined in the United States by
 standards issued by the National Information Standards Organization
 (NISO) and also by parallel international standards issued under the
 auspices of the International Organization for Standardization (ISO).
 NISO is the ANSI-accredited standards body serving libraries,
 publishers and information services.  The SICI code is defined by a
 NISO document in the United States and does not have a parallel
 international standards document at present.

Lynch, et. al. Informational [Page 2] RFC 2288 Bibligraphic Identifiers February 1998

 Many other bibliographic identifiers are in common use (for example,
 CODEN, numbers assigned by major bibliographic utilities such as OCLC
 and RLG, national library numbers such as the Library of Congress
 Control Number) or are under development.  While we do not discuss
 them in this document, many of these will also need to be supported
 within the URN framework as it moves to large scale implementation.
 The issues involved in supporting those additional identifiers are
 anticipated to be broadly similar to those involved in supporting
 ISBNs, ISSNs, and SICIs.

2. Identification vs. Resolution

 It is important to distinguish between the resource identified by a
 URN and the resources a URN resolver that can reasonably return when
 attempting to resolve an identifier.  For example, the ISSN 0040-781X
 identifies the popular magazine "Time" -- all of it, every issue for
 from the start of publication to present.  Resolving such an
 identifier should not result in the equivalent of hundreds of
 thousands of pages of text and photos being dumped to the user's
 machine.  It is more reasonable for ISSNs to resolve to a
 navigational system, such as an HTML-based search form, so the user
 may select issues or articles of interest.  ISBNs and SICIs, on the
 other hand, do identify finite, manageably-sized objects, but these
 objects may still be large enough that resolution to a hierarchical
 system is appropriate.
 In addition, the materials identified by an ISSN, ISBN or SICI may
 exist only in printed or other physical form, not electronically.
 The best that a resolver may be able to offer is information about
 where to get the physical resource, such as library holdings or a
 bookstore or publisher order form.  The URN Framework provides
 resolution services that may be used to describe any differences
 between the resource identified by a URN and the resource that would
 be returned as a result of resolving that URN.

3. International Standard Book Numbers

3.1 Overview

 An International Standard Book Number (ISBN) identifies an edition of
 a monographic work.  The ISBN is defined by the standard
 NISO/ANSI/ISO 2108:1992 [ISO1]
 Basically, an ISBN is a ten-digit number (actually, the last digit
 can be the letter "X" as well, as described below) which is divided
 into four variable length parts usually separated by hyphens when
 printed.  The parts are as follows (in this order):

Lynch, et. al. Informational [Page 3] RFC 2288 Bibligraphic Identifiers February 1998

  • a group identifier which specifies a group of publishers, based on

national, geographic or some other criteria,

  • the publisher identifier,
  • the title identifier,
  • and a modulus 11 check digit, using X instead of 10.
 The group and publisher number assignments are managed in such a way
 that the hyphens are not needed to parse the ISBN unambiguously into
 its constituent parts.  However, the ISBN is normally transmitted and
 displayed with hyphens to make it easy for human beings to recognize
 these parts without having to make reference to or have knowledge of
 the number assignments for group and publisher identifiers.

3.2 Encoding Considerations and Lexical Equivalence

 Embedding ISBNs within the URN framework presents no particular
 encoding problems, since all of the characters that can appear in an
 ISBN are valid in the identifier segment of the URN.  %-encoding, as
 described in [MOATS] is never needed.
 Example: URN:ISBN:0-395-36341-1
 For the ISBN namespace, some additional equivalence rules are
 appropriate.  Prior to comparing two ISBN URNs for equivalence, it is
 appropriate to remove all hyphens, and to convert any occurrences of
 the letter X to upper case.

3.3 Additional considerations

 The ISBN standard and related community implementation guidelines
 define when different versions of a work should be assigned the same
 or differing ISBNs.  In actuality, however, practice varies somewhat
 depending on publisher as to whether different ISBNs are assigned for
 paperbound vs.  hardbound versions of the same work, electronic vs.
 printed versions of the same work, or versions of the same work
 distinguished in some other way (e.g., published for example in the
 US and in Europe).  The choice of whether to assign a new ISBN or to
 reuse an existing one when publishing a revised printing of an
 existing edition of a work or even a revised edition of a work is
 somewhat subjective.  Practice varies from publisher to publisher
 (indeed, the distinction between a revised printing and a new edition
 is itself somewhat subjective).  The use of ISBNs within the URN
 framework simply reflects these existing practices.  Note that it is
 likely that an ISBN URN will often resolve to many instances of the
 work (many URLs).

Lynch, et. al. Informational [Page 4] RFC 2288 Bibligraphic Identifiers February 1998

4. International Standard Serials Numbers

4.1 Overview

 International Standard Serials Numbers (ISSN) identify a work that is
 published on a continued basis in issues; they identify the entire
 (often open-ended, in the case of an actively published) work.  ISSNs
 are defined by the international standards ISO 3297:1986 [ISO2] and
 ISO/DIS 3297 [ISO3] and within the United States by NISO Z39.9-1992
 [NISO1].  The ISSN International Centre is located in Paris and
 coordinates a network of regional centers.  The National Serials Data
 Program within the Library of Congress is the US Center of this
 network.
 ISSNs have the form NNNN-NNNN where N is a digit, the last digit may
 be an upper case X as the result of the check character calculation.
 Unlike the ISBN the ISSN components do not have much structure;
 blocks of numbers are passed out to the regional centers and
 publishers.

4.2 Encoding Considerations and Lexical Equivalence

 Again, there is no problem representing ISSNs in the namespace-
 specific string of URNs since all characters valid in the ISSN are
 valid in the namespace-specific URN string, and %-encoding is never
 required.
 Example: URN:ISSN:1046-8188
 Supplementary comparison rules are also appropriate for the ISSN
 namespace.  Just as for ISBNs, hyphens should be dropped prior to
 comparison and occurrences of 'x' normalized to uppercase.

4.3 Additional Considerations

 The ISSN standard and related community implementation guidelines
 specify when new ISSNs should be assigned vs.  continuing to use an
 existing one.  There are some publications where practice within the
 bibliographic community varies from institution to institution, such
 as annuals or annual conference proceedings.  In some cases these are
 treated as serials and ISSNs are used, and in some cases they are
 treated as monographs and ISBNs are used.  For example SIGMOD Record
 volume 24 number 2 June 1995 contains the Proceedings of the 1995 ACM
 SIGMOD International Conference on Management of Data.  If you
 subscribe to the journal (ISSN 0163-5808) this is simply the June
 issue.  On the other hand you may have acquired this volume as the
 conference proceedings (a monograph) and as such would use the ISBN
 0-89791-731-6 to identify the work.  There are also varying practices

Lynch, et. al. Informational [Page 5] RFC 2288 Bibligraphic Identifiers February 1998

 within the publishing community as to when new ISSNs are assigned due
 to the change in the name of a periodical (e.g. Atlantic becomes
 Atlantic Monthly); or when a periodical is published both in printed
 and electronic versions (e.g. The New York Times).  The use of ISSNs
 in URNs will reflect these judgments and practices.

5. Serial Item and Contribution Identifiers

5.1 Overview

 The standard for Serial Item and Contribution Identifiers (SICI)
 codes, which has recently been extensively revised, is defined by
 NISO/ANSI Z39.56-1997 [NISO2].  The maintenance agency for the SICI
 code is the UnCover Corporation.
 SICI codes can be used to identify an issue of a serial, or a
 specific contribution (e.g., an article, or the table of contents)
 within an issue of a serial.  SICI codes are not assigned, they are
 constructed based on information about the issue or issue component
 in question.
 The complete syntax for the SICI code will not be discussed here; see
 NISO/ANSI Z39.56-1997 [NISO2] for details.  However, an example and
 brief review of the major components is needed to understand the
 relationship with the ISSN and how this identifier differs from an
 ISSN.  An example of a SICI code is: 0015-
 6914(19960101)157:1<62:KTSW>2.0.TX;2-F
 The first nine characters are the ISSN identifying the serial title.
 The second component, in parentheses, is the chronology information
 giving the date the particular serial issue was published.  In this
 example that date was January 1, 1996.  The third component, 157:1,
 is enumeration information (volume, number) for the particular issue
 of the serial.  These three components comprise the "item segment" of
 a SICI code.  By augmenting the ISSN with the chronology and/or
 enumeration information, specific issues of the serial can be
 identified.  The next segment, <62:KTSW>, identifies a particular
 contribution within the issue.  In this example we provide the
 starting page number and a title code constructed from the initial
 characters of the title.  Identifiers assigned to a contribution can
 be used in the contribution segment if page numbers are
 inappropriate.  The rest of the identifier is the control segment,
 which includes a check character.  Interested readers are encouraged
 to consult the standard for an explanation of the fields in that
 segment.

Lynch, et. al. Informational [Page 6] RFC 2288 Bibligraphic Identifiers February 1998

5.2 Encoding Considerations and Lexical Equivalence

 The character set for SICIs is intended to be email-transport-
 transparent, so it does not present major problems.  However, all
 printable excluded and reserved characters from the URN syntax are
 valid in the SICI character set and must be %-encoded.
 Example of a SICI for an issue of a journal:
            URN:SICI:1046-8188(199501)13:1%3C%3E1.0.TX;2-F
 For an article contained within that issue:
        URN:SICI:1046-8188(199501)13:1%3C69:FTTHBI%3E2.0.TX;2-4
 Equivalence rules for SICIs are not appropriate for definition as
 part of the namespace and incorporation in areas such as cache
 management algorithms.  It is best left to resolver systems which try
 to determine if two SICIs refer to the same content.  Consequently,
 we do not propose any specific rules for equivalence testing through
 lexical manipulation.

5.3 Additional Considerations

 Since the serial is identified by an ISSN, some of the ambiguity
 currently found in the assignment of ISSNs carries over into SICI
 codes.  In cases where an ISSN may refer to a serial that exists in
 multiple formats, the SICI contains a qualifier that specifies the
 format type (for example, print, microform, or electronic).  SICI
 codes may be constructed from a variety of sources (the actual issue
 of the  serial, a citation or a record from an abstracting service)
 and, as such are based on the principle of using all available
 information, so there may be multiple SICI codes representing the
 same article [NISO2, Appendix D].  For example, one code might be
 constructed with access to both chronology and enumeration (that is,
 date of issue and volume, issue and page number), another code might
 be constructed based only on enumeration information and without
 benefit of chronology.  Systems that use SICI codes employ complex
 matching algorithms to try to match SICI codes constructed from
 incomplete information to SICI codes constructed with the benefit of
 all relevant information.

Lynch, et. al. Informational [Page 7] RFC 2288 Bibligraphic Identifiers February 1998

6. Security Considerations

 This document proposes means of encoding several existing
 bibliographic identifiers within the URN framework. This document
 does not discuss resolution; thus questions of secure or
 authenticated resolution mechanisms are out of scope.  It does not
 address means of validating the integrity or authenticating the
 source or provenance of URNs that contain bibliographic identifiers.
 Issues regarding intellectual property rights associated with objects
 identified by the various bibliographic identifiers are also beyond
 the scope of this document, as are questions about rights to the
 databases that might be used to construct resolvers.

7. References

 [ISO1] NISO/ANSI/ISO 2108:1992 Information and documentation
       -- International standard book number (ISBN)
 [ISO2] ISO 3297:1986 Documentation -- International standard
       serial numbering (ISSN)
 [ISO3] ISO/DIS 3297 Information and documentation --
       International standard serial numbering (ISSN) (Revision of ISO
       3297:1986)
 [Moats] Moats, R., "URN Syntax", RFC 2141, May 1997.
 [NISO 1] NISO/ANSI Z39.9-1992 International standard serial
       numbering (ISSN)
 [NISO 2] NISO/ANSI Z39.56-1997 Serial Item and Contribution
       Identifier
 [Sollins & Masinter] Sollins, K., and L. Masinter, "Functional
       Requirements for Uniform Resource Names", RFC 1737, December
       1994.

Lynch, et. al. Informational [Page 8] RFC 2288 Bibligraphic Identifiers February 1998

8. Authors' Addresses

 Clifford Lynch
 Executive Director
 Coalition for Networked Information
 21 Dupont Circle
 Washington, DC 20036
 EMail: cliff@cni.org
 Cecilia Preston
 Preston & Lynch
 PO Box 8310
 Emeryville, CA 94662
 EMail: cecilia@well.com
 Ron Daniel Jr.
 Advanced Computing Lab, MS B287
 Los Alamos National Laboratory
 Los Alamos, NM, 87545
 EMail: rdaniel@acl.lanl.gov

Lynch, et. al. Informational [Page 9] RFC 2288 Bibligraphic Identifiers February 1998

9. 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.

Lynch, et. al. Informational [Page 10]

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