2004/id/draft-ietf-urn-biblio-01.txt


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
                             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.

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.

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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

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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.

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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)

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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

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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.

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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.


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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

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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:

     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

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

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

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 [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
Executive Director
Coalition for Networked Information
21 Dupont Circle
Washington, DC 20036
cliff@cni.org

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
rdaniel@acl.lanl.gov


                                                    [Page 11]


1
2	Internet Draft Clifford Lynch
3	September 8. 1997 Coalition for Networked Information
4	draft-ietf-urn-biblio-01.txt Cecilia Preston
5	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.
30
31	This document does not specify a standard; it is purely
32	informational.
33
34
35	0. Abstract
36
37	A system for Uniform Resource Names (URNs) must be capable
38	of supporting identifiers from existing widely-used naming
39	systems. This document discusses how three major
40	bibliographic identifiers (the ISBN, ISSN and SICI) can be
41	supported within the URN framework and the currently
42	proposed syntax for URNs.
43
44	[Page 1]
45
46	INTERNET DRAFT: Bibliographic Identifiers as URNs 9/1997
47
48
49	1. Introduction
50
51	The ongoing work of several IETF working groups, most
52	recently in the Uniform Resource Names working group, has
53	culminated the development of a syntax for Uniform Resource
54	Names (URNs). The functional requirements and overall
55	framework for Uniform Resource Names are specified in RFC
56	1737 [Sollins & Masinter] and the specification for the
57	URN syntax is RFC 2141 [Moats].
58
59	As part of the validation process for the development of
60	URNs the IETF working group has agreed that it is important
61	to demonstrate that the current URN syntax proposal can
62	accommodate existing identifiers from well established
63	namespaces. One such infrastructure for assigning and
64	managing names comes from the bibliographic community.
65	Bibliographic identifiers function as names for objects that
66	exist both in print and, increasingly, in electronic formats.
67	This Internet draft demonstrates the feasibility of
68	supporting three representative bibliographic identifiers
69	within the currently proposed URN framework and syntax.
70
71	Note that this document does not purport to define the
72	"official" standard way ofmoving these bibliographic
73	identifiers into URNs; it merely demonstrates feasibility.
74	It has not been developed in consultation with these
75	standards bodies and maintenance agencies that oversee the
76	existing bibliographic identifiers. Any actual Internet
77	standard for encoding these bibliographic identifiers as
78	URNs will need to be developed in consultation with the
79	responsible standards bodies and maintenance agencies.
80
81	In addition, there are several open questions with regard to
82	the management and registry of Namespace Identifiers (NIDs)
83	for URNs. For purposes of illustration, we have used the
84	three NIDs "ISBN", "ISSN" and "SICI" for the three
85	corresponding bibliographic identifiers discussed in this
86	document. While we believe this to be the most appropriate
87	choice, it is not the only one. The NIDs could be based on
88
89	[Page 2]
90
91	INTERNET DRAFT: Bibliographic Identifiers as URNs 9/1997
92
93
94	the standards body and standard number (e.g. "US-ANSI-NISO-
95	Z39.56-1997" rather than "SICI"). Alternatively, one could
96	lump all bibliographic identifiers into a single
97	"BIBLIOGRAPHIC" name space, and structure the namespace-
98	specific string to specify which identifier is being used.
99	Any final resolution of this must wait for the outcome of
100	namespace management discussions in the working group and
101	the broader IETF community.
102
103	For the purposes of this document, we have selected three
104	major bibliographic identifiers (national and international)
105	to fit within the URN framework. These are the International
106	Standard Book Number (ISBN) [ISO1], the International
107	Standard Serials Number (ISSN) [NISO1,ISO2, ISO3], and the
108	Serial Item and Contribution Identifier (SICI) [NISO2]. An
109	ISBN is used to identify a monograph (book). An ISSN is used
110	to identify serial publications (journals, newspapers) as a
111	whole. A SICI augments the ISSN in order to identify
112	individual issues of serial publications, or components
113	within those issues (such as an individual article, or the
114	table of contents of a given issue). The ISBN and ISSN are
115	defined in the United States by standards issued by the
116	National Information Standards Organization (NISO) and also
117	by parallel international standards issued under the auspices
118	of the International Organization for Standardization (ISO).
119	NISO is the ANSI-accredited standards body serving libraries,
120	publishers and information services. The SICI code is
121	defined by a NISO document in the United States and does not
122	have a parallel international standards document at present.
123
124	Many other bibliographic identifiers are in common use (for
125	example, CODEN, numbers assigned by major bibliographic
126	utilities such as OCLC and RLG, national library numbers such
127	as the Library of Congress Control Number) or are under
128	development. While we do not discuss them in this document,
129	many of these will also need to be supported within the URN
130	framework as it moves to large scale implementation. The
131	issues involved in supporting those additional identifiers
132	are anticipated to be broadly similar to those involved in
133	supporting ISBNs, ISSNs, and SICIs.
134
135	[Page 3]
136
137	INTERNET DRAFT: Bibliographic Identifiers as URNs 9/1997
138
139
140	2. Identification vs. Resolution
141
142	It is important to distinguish between the resource
143	identified by a URN and the resources a URN resolver that can
144	reasonably return when attempting to resolve an identifier.
145	For example, the ISSN 0040-781X identifies the popular
146	magazine "Time" -- all of it, every issue for from the start
147	of publication to present. Resolving such an identifier
148	should not result in the equivalent of hundreds of thousands
149	of pages of text and photos being dumped to the user's
150	machine. It is more reasonable for ISSNs to resolve to a
151	navigational system, such as an HTML-based search form, so
152	the user may select issues or articles of interest. ISBNs
153	and SICIs, on the other hand, do identify finite, manageably-
154	sized objects, but these objects may still be large enough
155	that resolution to a hierarchical system is appropriate.
156
157	In addition, the materials identified by an ISSN, ISBN or
158	SICI may exist only in printed or other physical form, not
159	electronically. The best that a resolver may be able to
160	offer is information about where to get the physical
161	resource, such as library holdings or a bookstore or
162	publisher order form. The URN Framework provides resolution
163	services that may be used to describe any differences
164	between the resource identified by a URN and the resource
165	that would be returned as a result of resolving that URN.
166
167
168	3. International Standard Book Numbers
169
170	3.1 Overview
171
172	An International Standard Book Number (ISBN) identifies an
173	edition of a monographic work. The ISBN is defined by the
174	standard NISO/ANSI/ISO 2108:1992 [ISO1]
175
176	Basically, an ISBN is a ten-digit number (actually, the last
177	digit can be the letter "X" as well, as described below)
178
179	[Page 4]
180
181	INTERNET DRAFT: Bibliographic Identifiers as URNs 9/1997
182
183
184	which is divided into four variable length parts usually
185	separated by hyphens when printed. The parts are as follows
186	(in this order):
187
188	* a group identifier which specifies a group of publishers,
189	based on national, geographic or some other criteria,
190
191	* the publisher identifier,
192
193	* the title identifier,
194
195	* and a modulus 11 check digit, using X instead of 10.
196
197	The group and publisher number assignments are managed in
198	such a way that the hyphens are not needed to parse the ISBN
199	unambiguously into its constituent parts. However, the ISBN
200	is normally transmitted and displayed with hyphens to make
201	it easy for human beings to recognize these parts without
202	having to make reference to or have knowledge of the number
203	assignments for group and publisher identifiers.
204
205	3.2 Encoding Considerations and Lexical Equivalance
206
207	Embedding ISBNs within the URN framework presents no
208	particular encoding problems, since all of the characters
209	that can appear in an ISBN are valid in the identifier
210	segment of the URN. %-encoding, as described in [MOATS] is
211	never needed.
212
213	Example: URN:ISBN:0-395-36341-1
214
215	For the ISBN namespace, some additional equivalence rules
216	are appropriate. Prior to comparing two ISBN URNs for
217	equivalence, it is appropriate to remove all hyphens, and to
218	convert any occurrences of the letter X to upper case.
219
220	3.3 Additional considerations
221
222	The ISBN standard and related community implementation
223	guidelines define when different versions of a work should
224
225	[Page 5]
226
227	INTERNET DRAFT: Bibliographic Identifiers as URNs 9/1997
228
229
230	be assigned the same or differing ISBNs. In actuality,
231	however, practice varies somewhat depending on publisher as
232	to whether different ISBNs are assigned for paperbound vs.
233	hardbound versions of the same work, electronic vs. printed
234
235	versions of the same work, or versions of the same work
236	distinguished in some other way (e.g.published for example in
237	the US and in Europe). The choice of whether to assign a new
238	ISBN or to reuse an existing one when publishing a revised
239	printing of an existing edition of a work or even a revised
240	edition of a work is somewhat subjective. Practice varies
241	from publisher to publisher (indeed, the distinction between
242	a revised printing and a new edition is itself somewhat
243	subjective). The use of ISBNs within the URN framework
244	simply reflects these existing practices. Note that it is
245	likely that an ISBN URN will often resolve to many instances
246	of the work (many URLs).
247
248	4. International Standard Serials Numbers
249
250	4.1 Overview
251
252	International Standard Serials Numbers (ISSN) identify a
253	work that is published on a continued basis in issues; they
254	identify the entire (often open-ended, in the case of an
255	actively published) work. ISSNs are defined by the
256	international standards ISO 3297:1986 [ISO2] and ISO/DIS
257	3297 [ISO3] and within the United States by NISO Z39.9-1992
258	[NISO1]. The ISSN International Centre is located in Paris and coordinates
259	a network of regional centers. The National
260	Serials Data Program within the Library of Congress is the US
261	Center of this network.
262
263	ISSNs have the form NNNN-NNNN where N is a digit, the last
264	digit may be an upper case X as the result of the check
265	character calculation. Unlike the ISBN the ISSN components
266	do not have much structure; blocks of numbers are passed out
267	to the regional centers and publishers.
268
269	[Page 6]
270
271
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274
275	4.2 Encoding Considerations and Lexical Equivalance
276
277	Again, there is no problem representing ISSNs in the
278	namespace-specific string of URNs since all characters valid
279	in the ISSN are valid in the namespace-specific URN string,
280	and %-encoding is never required.
281
282	Example: URN:ISSN:1046-8188
283
284	Supplementary comparison rules are also appropriate for the
285	ISSN namespace. Just as for ISBNs, hyphens should be
286	dropped prior to comparison and occurrences of 'x'
287	normalized to uppercase.
288
289	4.3 Additional Considerations
290
291	The ISSN standard and related community implementation
292	guidelines specify when new ISSNs should be assigned vs.
293	continuing to use an existing one. There are some
294	publications where practice within the bibliographic
295	community varies from institution to insitution, such as
296	annuals or annual conference proceedings. In some cases
297	these are treated as serials and ISSNs are used, and in some
298	cases they are treated as monographs and ISBNs are used. For
299	example SIGMOD Record volume 24 number 2 June 1995 contains
300	the Proceedings of the 1995 ACM SIGMOD International
301	Conference on Management of Data. If you subscribe to the
302	journal (ISSN 0163-5808) this is simply the June issue. On
303	the other hand you may have acquired this volume as the
304	conference proceedings (a monograph) and as such would use
305	the ISBN 0-89791-731-6 to identify the work. There are also
306	varying practices within the publishing community as to when
307	new ISSNs are assigned due to the change in the name of a
308	periodical (e.g. Atlantic becomes Atlantic Monthly); or when
309	a periodical is published both in printed and electronic
310	versions (e.g. The New York Times). The use of ISSNs in URNs
311	will reflect these judgments and practices.
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319
320	5. Serial Item and Contribution Identifiers
321
322	5.1 Overview
323
324	The standard for Serial Item and Contribution Identifiers
325	(SICI) codes, which has recently been extensively revised,
326	is defined by NISO/ANSI Z39.56-1997 [NISO2]. The maintenance
327	agency for the SICI code is the UnCover Corporation.
328
329	SICI codes can be used to identify an issue of a serial, or
330	a specific contribution (e.g., an article, or the table of
331	contents) within an issue of a serial. SICI codes are not
332	assigned, they are constructed based on information about
333	the issue or issue component in question.
334
335	The complete syntax for the SICI code will not be discussed
336	here; see NISO/ANSI Z39.56-1997 [NISO2] for details.
337	However, an example and brief review of the major components
338	is needed to understand the relationship with the ISSN and
339	how this identifier differs from an ISSN. An example of a
340	SICI code is: 0015-6914(19960101)157:1<62:KTSW>2.0.TX;2-F
341
342	The first nine characters are the ISSN identifying the
343	serial title. The second component, in parentheses, is the
344	chronology information giving the date the particular serial
345	issue was published. In this example that date was January
346	1, 1996. The third component, 157:1, is enumeration
347	information (volume, number) for the particular issue of the
348	serial. These three components comprise the "item segment"
349	of a SICI code. By augmenting the ISSN with the chronology
350	and/or enumeration information, specific issues of the
351	serial can be identified. The next segment, <62:KTSW>,
352	identifies a particular contribution within the issue. In
353	this example we provide the starting page number and a title
354	code constructed from the initial characters of the title.
355	Identifiers assigned to a contribution can be used in the
356	contribution segment if page numbers are inappropriate. The
357	rest of the identifier is the control segment, which
358	includes a check character. Interested readers are
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364
365	encouraged to consult the standard for an explanation of the
366	fields in that segment.
367
368	5.2 Encoding Considerations and Lexical Equivalance
369
370	The character set for SICIs is intended to be email-
371	transport-transparent, so it does not present major problems.
372	However, all printable excluded and reserved characters from
373	the URN syntax are valid in the SICI character set and must
374	be %-encoded.
375
376	Example of a SICI for an issue of a journal:
377
378	URN:SICI:1046-8188(199501)13:1%3C%3E1.0.TX;2-F
379
380	For an article contained within that issue:
381
382	URN:SICI:1046-8188(199501)13:1%3C69:FTTHBI%3E2.0.TX;2-4
383
384	Equivalence rules for SICIs are not appropriate for
385	definition as part of the namespace and incorporation in
386	areas such as cache management algorithms. It is best left
387	to resolver systems which try to determine if two SICIs refer
388	to the same content. Consequently, we do not propose any
389	specific rules for equivalence testing through lexical manipulation.
390
391	5.3 Additional Considerations
392
393	Since the serial is identified by an ISSN, some of the
394	ambiguity currently found in the assignment of ISSNs carries
395	over into SICI codes. In cases where an ISSN may refer to a
396	serial that exists in multiple formats, the SICI contains a
397	qualifier that specifies the format type (for example,
398	print, microform, or electronic). SICI codes may be
399	constructed from a variety of sources (the actual issue of
400	the serial, a citation or a record from an abstracting
401	service) and, as such are based on the principle of using
402	all available information, so there may be multiple SICI
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407	codes representing the same article [NISO2, Appenidx D].
408	For example, one code might be constructed with access to
409	both chronology and enumeration (that is, date of issue and
410	volume, issue and page number), another code might be
411	constructed based only on enumeration information and
412	without benefit of chronology. Systems that use SICI codes
413	employ complex matching algorithms to try to match SICI
414	codes constructed from incomplete information to SICI codes
415	constructed with the benefit of all relevant information.
416
417	6. Security Considerations
418
419	This document proposes means of encoding several existing
420	bibliographic identifiers within the URN framework. This
421	documentent does not discuss resolution; thus questions of
422	secure or authenticated resolution mechanisms are out of
423	scope. It does not address means of validating the integrity
424	or authenticating the source or provenance of URNs that
425	contain bibliographic identifiers. Issues regarding
426	intellectual property rights associated with objects
427	identified by the various bibliographic identifiers are also
428	beyond the scope of this document, as are questions about
429	rights to the databases that might be used to construct
430	resolvers.
431
432	7. References
433
434	[ISO1] NISO/ANSI/ISO 2108:1992 Information and documentation
435	-- International standard book number (ISBN)
436
437	[ISO2] ISO 3297:1986 Documentation -- International standard
438	serial numbering (ISSN)
439
440	[ISO3] ISO/DIS 3297 Information and documentation --
441	International standard serial numbering (ISSN)
442	(Revision of ISO 3297:1986)
443
444	[Moats] R. Moats, URN Syntax RFC 2141 May 1997.
445
446	[NISO 1] NISO/ANSI Z39.9-1992 International standard serial
447	numbering (ISSN)
448
449	[Page 10]
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453
454	[NISO 2] NISO/ANSI Z39.56-1997 Serial Item and Contribution
455	Identifier
456	[Sollins & Masinter] K. Sollins and L. Masinter, "Functional
457	Requirements for Uniform Resource Names", RFC 1737
458	December 1994.
459
460
461
462	8. Author's Addresses
463
464	Clifford Lynch
465	Executive Director
466	Coalition for Networked Information
467	21 Dupont Circle
468	Washington, DC 20036
469	cliff@cni.org
470
471	Cecilia Preston
472	Preston & Lynch
473	PO Box 8310
474	Emeryville, CA 94662
475	cecilia@well.com
476
477	Ron Daniel Jr.
478	Advanced Computing Lab, MS B287
479	Los Alamos National Laboratory
480	Los Alamos, NM, 87545
481	rdaniel@acl.lanl.gov
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