Skip to main content

Using Existing Bibliographic Identifiers as Uniform Resource Names

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 2288.
Authors Dr. Ron Daniel , Dr. Clifford A. Lynch , Cecilia M. Preston
Last updated 2013-03-02 (Latest revision 1997-09-10)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
Additional resources Mailing list discussion
Stream WG state (None)
Document shepherd (None)
IESG IESG state Became RFC 2288 (Informational)
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
Send notices to (None)
Internet Draft                                 Clifford Lynch
September 8. 1997         Coalition for Networked Information
draft-ietf-urn-biblio-01.txt                  Cecilia Preston
                                              Preston & Lynch
                                               Ron Daniel Jr.
                               Los Alamos National Laboratory

          Using Existing Bibliographic Identifiers
                   Uniform Resource Names

Status of this Document

This document is an Internet-Draft.  Internet-Drafts are
working documents of the Internet Engineering Task Force
(IETF), its areas, and its working groups.  Note that other
groups may also distribute working documents as Internet-

Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced or made obsolete by
other documents at any time.  It is inappropriate to use
Internet-Drafts as reference material or to cite them other
than as works in progress.

Distribution of this document is unlimited.

This document does not specify a standard; it is purely

0. 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.

                                                     [Page 1]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

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 Internet draft demonstrates the feasibility of
supporting three representative bibliographic identifiers
within the currently proposed URN framework and syntax.

Note that this document does not purport to define the
"official" standard way ofmoving 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

                                                     [Page 2]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

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.

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.

                                                     [Page 3]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

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)

                                                     [Page 4]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

which is divided into four variable length parts usually
separated by hyphens when printed.  The parts are as follows
(in this order):

* 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 Equivalance

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

                                                     [Page 5]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

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).

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.

                                                     [Page 6]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

4.2 Encoding Considerations and Lexical Equivalance

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 insitution, 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 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.

                                                     [Page 7]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

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

                                                     [Page 8]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

encouraged to consult the standard for an explanation of the
fields in that segment.

5.2 Encoding Considerations and Lexical Equivalance

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:


For an article contained within that issue:


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

                                                     [Page 9]
INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

codes representing the same article [NISO2, Appenidx 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.

6. Security Considerations

This document proposes means of encoding several existing
bibliographic identifiers within the URN framework. This
documentent 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

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] R. Moats, URN Syntax RFC 2141 May 1997.

[NISO 1] NISO/ANSI Z39.9-1992 International standard serial
      numbering (ISSN)

                                                    [Page 10]

INTERNET DRAFT: Bibliographic Identifiers as URNs      9/1997

 [NISO 2] NISO/ANSI Z39.56-1997 Serial Item and Contribution
[Sollins & Masinter] K. Sollins and L. Masinter, "Functional
       Requirements for Uniform Resource Names", RFC 1737
       December 1994.

8. Author's Addresses

Clifford Lynch
Executive Director
Coalition for Networked Information
21 Dupont Circle
Washington, DC 20036

Cecilia Preston
Preston & Lynch
PO Box 8310
Emeryville, CA 94662

Ron Daniel Jr.
Advanced Computing Lab, MS B287
Los Alamos National Laboratory
Los Alamos, NM, 87545

                                                    [Page 11]