2004/id/draft-ietf-urn-biblio-00.txt


Internet Draft                                Clifford Lynch
draft-ietf-urn-biblio-00.txt        University of California
22 March 1997                                Cecilia Preston
Expires in six months                        Preston & Lynch
                                              Ron Daniel Jr.
                              Los Alamos National Laboratory


          Using Existing Bibliographic Identifiers
                             as
                   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-
Drafts.

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.  Please send
comments to clifford.lynch@ucop.edu and cecilia@well.com.

This document does not specify a standard; it is purely
informational.


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     3/1997


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 current proposal for the
URN syntax is draft-ietf-urn-syntax-04.txt [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 managed
namespaces.  One such well-established 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 of doing so; it merely demonstrates
feasibility.  It has not been developed in consultation with
the 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-

                                                   [Page 2]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997

specific string to specify which identifier is being used.
We do not believe that these are advantageous approaches,
but must wait for the outcome of namespace management
discussions in the working group.

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].  ISBNs are used to identify monographs
(books).  ISSNs are used to identify serial publications
(journals, newspapers) as a whole.  SICIs augment 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, the 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 that can reasonably be
provided when attempting to resolve an identifier.  For

                                                    [Page 3]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997


example, the ISSN 0040-781X identifies the popular
"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 they 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 [ISO 1]

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):

* a group identifier which specifies a group of publishers,
based on national, geographic or some other criteria,

* the publisher identifier,

                                                   [Page 4]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997


* the title identifier,

* and a modulus 11 check digit, using X in lieu 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

Embedding ISBNs within the URN framework presents no
particular coding problems, since all of the characters that
can appear in an ISBN are valid in the identifier segment of
the URN.  %-encoding 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
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

                                                    [Page 5]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997


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 being 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
standards ISO 3297:1986 [ISO 2] and ISO/DIS 3297 [ISO 3] and
within the United States by NISO Z39.9-1992 [NISO 1].  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

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.


                                                    [Page 6]


INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997


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 site to site, 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 (Atlantic becomes Atlantic Monthly); or when a
periodical is published both in printed and electronic
versions (The New York Times).  The use of ISSNs as 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) has recently been extensively revised and is defined
by NISO/ANSI Z39.56-1997 [NISO 2].  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 (i.e., 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 for details.  However an
example and brief review of the major components is needed

                                                    [Page 7]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997


to understand the relationship with the ISSN and how this
identifier differs.  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) on 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.

5.2 Encoding Considerations

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 draft 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


                                                    [Page 8]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997


Special equivalence rules for SICIs are not appropriate for
definition as part of the namespace and incorporation in
areas such as cache management algorithms.  These are 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, 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.  It 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.

                                                    [Page 9]

INTERNET DRAFT:Bibliographic Identifiers as URNs     3/1997

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" draft-ietf-urn-syntax-
       04.text. March 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] K. Sollins and L. Masinter, "Functional
       Requirements for Uniform Resource Names", RFC 1737
       December 1994.

8. Author's Addresses

Clifford Lynch
University of California Office of the President
300 Lakeside Drive, 8th floor
Oakland CA 94612-3550
clifford.lynch@ucop.edu

Cecilia Preston
Preston & Lynch
PO Box 8310
Emeryville, CA 94662
cecilia@well.com

Ron Daniel Jr.
Advanced Computing Lab, MS B287
Los Alamos National Laboratory
Los Alamos, NM, 87545
voice: +1 505 665 0597
fax: +1 505 665 4939
http://www.acl.lanl.gov/~rdaniel


                                                   [Page 10]


1
2	Internet Draft Clifford Lynch
3	draft-ietf-urn-biblio-00.txt University of California
4	22 March 1997 Cecilia Preston
5	Expires in six months Preston & Lynch
6	Ron Daniel Jr.
7	Los Alamos National Laboratory
8
9
10	Using Existing Bibliographic Identifiers
11	as
12	Uniform Resource Names
13
14
15	Status of this Document
16
17	This document is an Internet-Draft. Internet-Drafts are
18	working documents of the Internet Engineering Task Force
19	(IETF), its areas, and its working groups. Note that other
20	groups may also distribute working documents as Internet-
21	Drafts.
22
23	Internet-Drafts are draft documents valid for a maximum of
24	six months and may be updated, replaced or made obsolete by
25	other documents at any time. It is inappropriate to use
26	Internet-Drafts as reference material or to cite them other
27	than as works in progress.
28
29	Distribution of this document is unlimited. Please send
30	comments to clifford.lynch@ucop.edu and cecilia@well.com.
31
32	This document does not specify a standard; it is purely
33	informational.
34
35
36	0. Abstract
37
38	A system for Uniform Resource Names (URNs) must be capable
39	of supporting identifiers from existing widely-used naming
40	systems. This document discusses how three major
41	bibliographic identifiers (the ISBN, ISSN and SICI) can be
42	supported within the URN framework and the currently
43	proposed syntax for URNs.
44
45
46
47	[Page 1]
48
49	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
50
51
52	1. Introduction
53
54	The ongoing work of several IETF working groups, most
55	recently in the Uniform Resource Names working group, has
56	culminated the development of a syntax for Uniform Resource
57	Names (URNs). The functional requirements and overall
58	framework for Uniform Resource Names are specified in RFC
59	1737 [Sollins & Masinter] and the current proposal for the
60	URN syntax is draft-ietf-urn-syntax-04.txt [Moats].
61
62	As part of the validation process for the development of
63	URNs the IETF working group has agreed that it is important
64	to demonstrate that the current URN syntax proposal can
65	accommodate existing identifiers from well managed
66	namespaces. One such well-established infrastructure for
67	assigning and managing names comes from the bibliographic
68	community. Bibliographic identifiers function as names for
69	objects that exist both in print and, increasingly, in
70	electronic formats. This Internet draft demonstrates the
71	feasibility of supporting three representative bibliographic
72	identifiers within the currently proposed URN framework and
73	syntax.
74
75	Note that this document does not purport to define the
76	"official" standard way of doing so; it merely demonstrates
77	feasibility. It has not been developed in consultation with
78	the standards bodies and maintenance agencies that oversee
79	the existing bibliographic identifiers. Any actual Internet
80	standard for encoding these bibliographic identifiers as
81	URNs will need to be developed in consultation with the
82	responsible standards bodies and maintenance agencies.
83
84	In addition, there are several open questions with regard to
85	the management and registry of Namespace Identifiers (NIDs)
86	for URNs. For purposes of illustration, we have used the
87	three NIDs "ISBN", "ISSN" and "SICI" for the three
88	corresponding bibliographic identifiers discussed in this
89	document. While we believe this to be the most appropriate
90	choice, it is not the only one. The NIDs could be based on
91	the standards body and standard number (e.g. "US-ANSI-NISO-
92	Z39.56-1997" rather than "SICI"). Alternatively, one could
93	lump all bibliographic identifiers into a single
94	"BIBLIOGRAPHIC" name space, and structure the namespace-
95
96	[Page 2]
97
98	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
99
100	specific string to specify which identifier is being used.
101	We do not believe that these are advantageous approaches,
102	but must wait for the outcome of namespace management
103	discussions in the working group.
104
105	For the purposes of this document, we have selected three
106	major bibliographic identifiers (national and international)
107	to fit within the URN framework. These are the
108	International Standard Book Number (ISBN) [ISO1], the
109	International Standard Serials Number (ISSN) [NISO1,ISO2,
110	ISO3], and the Serial Item and Contribution Identifier
111	(SICI) [NISO2]. ISBNs are used to identify monographs
112	(books). ISSNs are used to identify serial publications
113	(journals, newspapers) as a whole. SICIs augment the ISSN
114	in order to identify individual issues of serial
115	publications, or components within those issues (such as an
116	individual article, or the table of contents of a given
117	issue). The ISBN and ISSN are defined in the United States
118	by standards issued by the National Information Standards
119	Organization (NISO) and also by parallel international
120	standards issued under the auspices of the International
121	Organization for Standardization (ISO). NISO is the ANSI-
122	accredited standards body serving libraries, publishers and
123	information services. The SICI code is defined by a NISO
124	document in the United States and does not have a parallel
125	international standards document at present.
126
127	Many other bibliographic identifiers are in common use (for
128	example, the CODEN, numbers assigned by major bibliographic
129	utilities such as OCLC and RLG, national library numbers
130	such as the Library of Congress Control Number) or are under
131	development. While we do not discuss them in this document,
132	many of these will also need to be supported within the URN
133	framework as it moves to large scale implementation. The
134	issues involved in supporting those additional identifiers
135	are anticipated to be broadly similar to those involved in
136	supporting ISBNs, ISSNs, and SICIs.
137
138
139	2. Identification vs. Resolution
140
141	It is important to distinguish between the resource
142	identified by a URN and the resources that can reasonably be
143	provided when attempting to resolve an identifier. For
144
145	[Page 3]
146
147	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
148
149
150	example, the ISSN 0040-781X identifies the popular
151	"Time". All of it, every issue for from the start of
152	publication to present. Resolving such an identifier should
153	not result in the equivalent of hundreds of thousands of
154	pages of text and photos being dumped to the user's machine.
155	It is more reasonable for ISSNs to resolve to a navigational
156	system, such as an HTML-based search form, so the user may
157	select issues or articles of interest. ISBNs and SICIs, on
158	the other hand, do identify finite, manageably-sized
159	objects, but they may still be large enough that resolution
160	to a hierarchical system is appropriate.
161
162	In addition, the materials identified by an ISSN, ISBN or
163	SICI may exist only in printed or other physical form, not
164	electronically. The best that a resolver may be able to
165	offer is information about where to get the physical
166	resource, such as library holdings or a bookstore or
167	publisher order form. The URN Framework provides resolution
168	services that may be used to describe any differences
169	between the resource identified by a URN and the resource
170	that would be returned as a result of resolving that URN.
171
172
173	3. International Standard Book Numbers
174
175	3.1 Overview
176
177	An International Standard Book Number (ISBN) identifies an
178	edition of a monographic work. The ISBN is defined by the
179	standard NISO/ANSI/ISO 2108:1992 [ISO 1]
180
181	Basically, an ISBN is a ten-digit number (actually, the last
182	digit can be the letter "X" as well, as described below)
183	which is divided into four variable length parts usually
184	separated by hyphens when printed. The parts are as follows
185	(in this order):
186
187	* a group identifier which specifies a group of publishers,
188	based on national, geographic or some other criteria,
189
190	* the publisher identifier,
191
192	[Page 4]
193
194	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
195
196
197	* the title identifier,
198
199	* and a modulus 11 check digit, using X in lieu of 10.
200
201	The group and publisher number assignments are managed in
202	such a way that the hyphens are not needed to parse the ISBN
203	unambiguously into its constituent parts. However, the ISBN
204	is normally transmitted and displayed with hyphens to make
205	it easy for human beings to recognize these parts without
206	having to make reference to or have knowledge of the number
207	assignments for group and publisher identifiers.
208
209	3.2 Encoding Considerations
210
211	Embedding ISBNs within the URN framework presents no
212	particular coding problems, since all of the characters that
213	can appear in an ISBN are valid in the identifier segment of
214	the URN. %-encoding is never needed.
215
216	Example: URN:ISBN:0-395-36341-1
217
218	For the ISBN namespace, some additional equivalence rules
219	are appropriate. Prior to comparing two ISBN URNs for
220	equivalence, it is appropriate to remove all hyphens, and to
221	convert any occurrences of the letter X to upper case.
222
223	3.3 Additional considerations
224
225	The ISBN standard and related community implementation
226	guidelines define when different versions of a work should
227	be assigned the same or differing ISBNs. In actuality,
228	however, practice varies somewhat depending on publisher as
229	to whether different ISBNs are assigned for paperbound vs.
230	hardbound versions of the same work, electronic vs. printed
231	versions of the same work, or versions of the same work
232	published for example in the US and in Europe. The choice
233	of whether to assign a new ISBN or to reuse an existing one
234	when publishing a revised printing of an existing edition of
235	a work or even a revised edition of a work is somewhat
236	subjective. Practice varies from publisher to publisher
237	(indeed, the distinction between a revised printing and a
238	new edition is itself somewhat subjective). The use of
239
240	[Page 5]
241
242	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
243
244
245	ISBNs within the URN framework simply reflects these
246	existing practices. Note that it is likely that an ISBN URN
247	will often resolve to many instances of the work (many
248	URLs).
249
250
251	4. International Standard Serials Numbers
252
253	4.1 Overview
254
255	International Standard Serials Numbers (ISSN) identify a
256	work that is being published on a continued basis in issues;
257	they identify the entire (often open-ended, in the case of
258	an actively published) work. ISSNs are defined by the
259	standards ISO 3297:1986 [ISO 2] and ISO/DIS 3297 [ISO 3] and
260	within the United States by NISO Z39.9-1992 [NISO 1]. The
261	ISSN International Centre is located in Paris and
262	coordinates a network of regional centers. The National
263	Serials Data Program within the Library of Congress is the
264	US Center of this network.
265
266	ISSNs have the form NNNN-NNNN where N is a digit, the last
267	digit may be an upper case X as the result of the check
268	character calculation. Unlike the ISBN the ISSN components
269	do not have much structure; blocks of numbers are passed out
270	to the regional centers and publishers.
271
272	4.2 Encoding Considerations
273
274	Again, there is no problem representing ISSNs in the
275	namespace-specific string of URNs since all characters valid
276	in the ISSN are valid in the namespace-specific URN string,
277	and %-encoding is never required.
278
279	Example: URN:ISSN:1046-8188
280
281	Supplementary comparison rules are also appropriate for the
282	ISSN namespace. Just as for ISBNs, hyphens should be
283	dropped prior to comparison and occurrences of 'x'
284	normalized to uppercase.
285
286
287	[Page 6]
288
289
290	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
291
292
293	4.3 Additional Considerations
294
295	The ISSN standard and related community implementation
296	guidelines specify when new ISSNs should be assigned vs.
297	continuing to use an existing one. There are some
298	publications where practice within the bibliographic
299	community varies from site to site, such as annuals or
300	annual conference proceedings. In some cases these are
301	treated as serials and ISSNs are used, and in some cases
302	they are treated as monographs and ISBNs are used. For
303	example SIGMOD Record volume 24 number 2 June 1995 contains
304	the Proceedings of the 1995 ACM SIGMOD International
305	Conference on Management of Data. If you subscribe to the
306	journal (ISSN 0163-5808) this is simply the June issue. On
307	the other hand you may have acquired this volume as the
308	conference proceedings (a monograph) and as such would use
309	the ISBN 0-89791-731-6 to identify the work. There are also
310	varying practices within the publishing community as to when
311	new ISSNs are assigned due to the change in the name of a
312	periodical (Atlantic becomes Atlantic Monthly); or when a
313	periodical is published both in printed and electronic
314	versions (The New York Times). The use of ISSNs as URNs
315	will reflect these judgments and practices.
316
317
318	5. Serial Item and Contribution Identifiers
319
320	5.1 Overview
321
322	The standard for Serial Item and Contribution Identifiers
323	(SICI) has recently been extensively revised and is defined
324	by NISO/ANSI Z39.56-1997 [NISO 2]. The maintenance agency
325	for the SICI code is the UnCover Corporation.
326
327	SICI codes can be used to identify an issue of a serial, or
328	a specific contribution (i.e., an article, or the table of
329	contents) within an issue of a serial. SICI codes are not
330	assigned, they are constructed based on information about
331	the issue or issue component in question.
332
333	The complete syntax for the SICI code will not be discussed
334	here; see NISO/ANSI Z39.56-1997 for details. However an
335	example and brief review of the major components is needed
336
337	[Page 7]
338
339	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
340
341
342	to understand the relationship with the ISSN and how this
343	identifier differs. An example of a SICI code is:
344
345	0015-6914(19960101)157:1<62:KTSW>2.0.TX;2-F
346
347	The first nine characters are the ISSN identifying the
348	serial title. The second component, in parentheses, is the
349	chronology information giving the date the particular serial
350	issue was published. In this example that date was January
351	1, 1996. The third component, 157:1, is enumeration
352	information (volume, number) on the particular issue of the
353	serial. These three components comprise the "item segment"
354	of a SICI code. By augmenting the ISSN with the chronology
355	and/or enumeration information, specific issues of the
356	serial can be identified. The next segment, <62:KTSW>,
357	identifies a particular contribution within the issue. In
358	this example we provide the starting page number and a title
359	code constructed from the initial characters of the title.
360	Identifiers assigned to a contribution can be used in the
361	contribution segment if page numbers are inappropriate. The
362	rest of the identifier is the control segment, which
363	includes a check character. Interested readers are
364	encouraged to consult the standard for an explanation of the
365	fields in that segment.
366
367	5.2 Encoding Considerations
368
369	The character set for SICIs is intended to be email-
370	transport-transparent, so it does not present major
371	problems. However, all printable excluded and reserved
372	characters from the URN syntax draft are valid in the SICI
373	character set and must be %-encoded.
374
375	Example of a SICI for an issue of a journal
376
377	URN:SICI:1046-8188(199501)13:1%3C%3E1.0.TX;2-F
378
379	For an article contained within that issue
380
381	URN:SICI:1046-8188(199501)13:1%3C69:FTTHBI%3E2.0.TX;2-4
382
383
384	[Page 8]
385
386	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
387
388
389	Special equivalence rules for SICIs are not appropriate for
390	definition as part of the namespace and incorporation in
391	areas such as cache management algorithms. These are best
392	left to resolver systems which try to determine if two SICIs
393	refer to the same content. Consequently, we do not propose
394	any specific rules for equivalence testing through lexical
395	manipulation.
396
397	5.3 Additional Considerations
398
399	Since the serial is identified by an ISSN, some of the
400	ambiguity currently found in the assignment of ISSNs carries
401	over into SICI codes. In cases where an ISSN may refer to a
402	serial that exists in multiple formats, the SICI contains a
403	qualifier that specifies the format type (for example,
404	print, microform, or electronic). SICI codes may be
405	constructed from a variety of sources (the actual issue of
406	the serial, a citation or a record from an abstracting
407	service) and, as such are based on the principle of using
408	all available information, so there may be multiple SICI
409	codes representing the same article [NISO2, Appenidx D].
410	For example, one code might be constructed with access to
411	both chronology and enumeration (that is, date of issue and
412	volume, issue and page number), another code might be
413	constructed based only on enumeration information and
414	without benefit of chronology. Systems that use SICI codes
415	employ complex matching algorithms to try to match SICI
416	codes constructed from incomplete information to SICI codes
417	constructed with the benefit of all relevant information.
418
419	6. Security Considerations
420
421	This document proposes means of encoding several existing
422	bibliographic identifiers within the URN framework. It does
423	not discuss resolution; thus questions of secure or
424	authenticated resolution mechanisms are out of scope. It
425	does not address means of validating the integrity or
426	authenticating the source or provenance of URNs that contain
427	bibliographic identifiers. Issues regarding intellectual
428	property rights associated with objects identified by the
429	various bibliographic identifiers are also beyond the scope
430	of this document, as are questions about rights to the
431	databases that might be used to construct resolvers.
432
433	[Page 9]
434
435	INTERNET DRAFT:Bibliographic Identifiers as URNs 3/1997
436
437	7. References
438
439	[ISO1] NISO/ANSI/ISO 2108:1992 Information and documentation
440	-- International standard book number (ISBN)
441	[ISO2] ISO 3297:1986 Documentation -- International standard
442	serial numbering (ISSN)
443	[ISO3] ISO/DIS 3297 Information and documentation --
444	International standard serial numbering (ISSN)
445	(Revision of ISO 3297:1986)
446	[Moats] R. Moats, "URN Syntax" draft-ietf-urn-syntax-
447	04.text. March 1997
448	[NISO 1] NISO/ANSI Z39.9-1992 International standard serial
449	numbering (ISSN)
450	[NISO 2] NISO/ANSI Z39.56-1997 Serial Item and Contribution
451	Identifier
452	[Sollins & Masinter] K. Sollins and L. Masinter, "Functional
453	Requirements for Uniform Resource Names", RFC 1737
454	December 1994.
455
456	8. Author's Addresses
457
458	Clifford Lynch
459	University of California Office of the President
460	300 Lakeside Drive, 8th floor
461	Oakland CA 94612-3550
462	clifford.lynch@ucop.edu
463
464	Cecilia Preston
465	Preston & Lynch
466	PO Box 8310
467	Emeryville, CA 94662
468	cecilia@well.com
469
470	Ron Daniel Jr.
471	Advanced Computing Lab, MS B287
472	Los Alamos National Laboratory
473	Los Alamos, NM, 87545
474	voice: +1 505 665 0597
475	fax: +1 505 665 4939
476	http://www.acl.lanl.gov/~rdaniel
477
478
479
480
481	[Page 10]
482
483
484