Internet DRAFT - draft-hakala-istc


Network Working Group                                       Juha Hakala
Internet-Draft                              Helsinki University Library
Category: Informational                                     3 July 2002
Expires: 3 January 2003

            Using International Standard Text Work Codes as
                         Uniform Resource Names

Status of this Memo

This document is an Internet-Draft and is in full conformance with all 
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This document discusses how International Standard Text Work Codes 
(ISTCs; persistent and unique identifiers for textual works) can be 
supported within the URN framework and the syntax for URNs defined in 
RFC 2141 [Moats]. Analysis is in part based on the ideas expressed in 
RFC 2288 [Lynch], which analysed the use of ISSN, ISBN and SICI as URNs. 
Chapter 5 contains a URN namespace registration request modelled 
according to the template in RFC 2611 [Daigle et al.].

1. Introduction 

As part of the validation process for the development of URNs the IETF 
working group 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.  RFC 2288 [Lynch et. al.] 
investigated the feasibility of using three identifiers (ISBN, ISSN and 
ISTC) as URNs. 

As a result of a recent proliferation of manifestations of works 
(various printed and electronic versions of books, for instance) ISO has 
decided to develop a set of identifiers for works. These standards 
include International Standard Audiovisual Work Code (ISAN), 
International Standard Musical Work Code (ISWC) and International 
Standard Text Work Code (ISTC) [ISO]. 

These standards identify works (such as Brave New World by Aldous 
Huxley) and their manifestations (such as a translation of Brave new 
world into Finnish). Manifestations, like the first edition of the Brave 
new world by Chatto & Windus, London 1932, will never receive an ISTC 
but  it being a novel  an ISBN. ISTC and ISTC metadata will be  
efficient tools for bringing together all related works and expressions 
 like all translations of Brave new world  and all manifestations any 
work or expression may have.  

ISTC is an emerging ISO standard which will reach the status of a Draft 
International Standard by Summer 2002. As of this writing it seems quite 
likely that the standard will be approved after the 6 months voting 
period in early 2003. Major changes to the syntax or to the maintenance 
organisation of the standard are very unlikely. 

RFC 2288 does not  and it was not the aim of its authors  to analyse 
how ISTC-based URNs can actually be resolved. This text will specify one 
solution to this question. There may be other complementary resolution 
services in addition to the one described here. 

Generally, the difficulty of designing a URN resolution service is 
dependent on two factors:

* Is the identifier dumb, or does it provide a hint on where to find a 
resolution service?

* How many potential resolution services are there?

ISBN (International Standard Book Number) is a good example of an 
intelligent identifier. Analysis of the ISBN will reveal not only the 
region where the ISBN has been assigned, but also the publisher of the 
book. Resolution of ISBN-based URNs can be decentralised to national 
bibliography databases, maintained by the national libraries. If the 
ISBN were a dumb identifier, this would be impossible.

International Standard Serial Number (ISSN) is a dumb identifier. It 
does not have a publisher identifier; serials published by a certain 
company get seemingly random ISSNs. Although ISSNs are allocated to 
regional agencies in blocks, which gives the system some "intelligence", 
a resolution service should not rely on these blocks  there are just 
too many of them, and their number is increasing all the time - but use 
the global ISSN database. It contains a bibliographic description of 
every periodical that has received an ISSN; by June 2002 the database 
contained about one million bibliographic records. Thus, it is easy to 
resolve ISSN-based URNs even though the identifier itself does not help 
in localising the resolution service.  

Like ISBN, ISTC will be an intelligent identifier (see below for a 
description of its syntax). On the other hand, it will be similar to the 
ISSN system in that there will be a global ISTC database, containing 
every ISTC assigned in the world, and related metadata. Since ISTCs can 
and will be given to textual works retrospectively, this database, 
maintained by the ISTC Registration Authority, will relatively soon 
become very large. 

However, at least some ISTC Regional Agencies, which will take care of 
ISTC assignment in their own regions (mainly geographical, but they may 
also be subject-driven) will send their data in batch mode to the ISTC 
register. Therefore there is a need to complement the ISTC resolution 
done in the global ISTC database with regional resolution services. The 
resulting system is a two-level cascade, where the bibliographic data 
related to the ISTC will be available either from the global database or 
from a database maintained by the Regional Agency, which assigned the 
ISTC. A Regional agency may be for instance a national library, which 
has generated work-related metadata and ISTCs from a traditional, 
manifestation-centered national bibliography. 
The registration request for acquiring a Namespace Identifier (NID) 
"ISTC" for International Standard Text Work Codes has been written by 
Helsinki University Library  The National Library of Finland on behalf 
of the International Standardisation Organisation (ISO). The request is 
included in chapter 5 of this text. 

The document at hand is part of a global co-operation of the national 
libraries to foster identification of electronic documents in general 
and utilisation of URNs in particular. This work is co-ordinated by a 
working group established by the Conference of Directors of National 
Libraries (CDNL), and supported by the Conference of the European 
National Librarians (CENL) Working Group on Networking Standards. 

We have used the URN Namespace Identifier "ISTC" for the International 
Standard Text Work Codes in examples below. 

2. Identification vs. Resolution

The ISTCs identify works, that is, abstract entities, which are embodied 
as physical manifestations. ISTC resolution service will only deliver a 
bibliographic record related to the work or expression. In the 
bibliographic record there may be links to other ISTC records describing 
related works and expressions, or to manifestations of the work. 

The manifestations of textual works identified by ISTCs may be printed 
or electronic. In the latter case, a user may be able to retrieve all 
manifestations related to the work. 

3. International Standard Text Work Code

3.1 Overview

The ISO International Standard Text Work Code (ISTC) standard defines a 
16 byte hexadecimal code that provides unique identification of textual 
works. ISTC is as of this writing specified in the committee draft 21047, 
revised in 15 May 2002. In this CD, comments given to the first committee 
draft have been taken into account, and the ISTC Working Group decided to 
publish the text as a Draft International Standard. Changes to the syntax 
or management of the ISTC at this stage are highly unlikely.  

ISTC consists of four segments, all of which are required:

-	registration agency element;
-	year element;
-	work element;
-	check digit. 

ISO CD 21047 provides the following example:

   ISTC 0A9 2002 12B4A105 7

When an ISTC is displayed in written form the letters ISTC shall precede 
it. The segments should be separated by hyphen or space. 

Registration agency element shall consist of three hexadecimal digits. 
The code (in the above example, 0A9) represents the Registration agency 
which assigned the ISTC. 

The year element (in the example, 2002) shall consist of the four digits 
representing the year in which the ISTC was allocated. 

The work element shall consist of eight hexadecimal digits. The work 
element shall be assigned by an ISTC Registration agency appointed by 
the Registration authority for ISO 21047. 

The check digit shall be calculated on a MOD 16-3 system defined in 
accordance with ISO 7064. 

ISTC Registration agencies must provide metadata for each work they have 
identified. This metadata will be collected into the global ISTC 
register maintained by the ISTC Registration authority. The data may be 
updated on-line or in batch mode. Duplicates are removed from the 
database with the help of a duplicate check algorithm.  

According to the ISO CD 21047, ISTCs can be applied retrospectively to old 
works. In such case, work metadata will be usually generated from existing 
manifestation level metadata. Some projects have already analysed the 
feasibility of this process with satisfactory results.

ISTC numbers are assigned by Registration agencies, which receive their 
agency element codes from the Registration authority. The system allows 
for 4096 such codes at any time; the codes may be re-used over time 
since agencies can be identified with the combination of the agency 
element and year. However, 4096 registration agency elements will be 
sufficient for quite a long time (the ISSN system has about 70 regional 
agencies, the ISBN system about 160). 

Given the relative complexity of ISTC codes and the very large number of 
textual works, which need identification, the recommended practice is to 
automate the ISTC creation process. In any Registration agency the 
agency element will never change, and changes in the year element are 
easy to track. Work element can be used rather freely, as long as the 
same identifier is never assigned twice. Since calculation of the check 
digit can also be easily automated, ISTC assignment can without 
difficulty be made a fully automatic process. 

3.2 Encoding Considerations and Lexical Equivalence

Since ISTC consists of hexadecimal characters, there are no needs for 
special encoding. However, the string ISTC preceding the identifier and 
any spaces separating the ISTC elements should be replaced by hyphens 
when an ISTC is used as URN. 

In order to determine if two ISTCs are lexically equivalent it is 
necessary to remove all spaces and hyphens from the ISTC string.  

3.3 Resolution of ISTC-based URNs

An efficient and global resolution service for ISTCs can be accomplished 
by using the global ISTC register. This database will, according to the 
current plans of the proposed Registration authority, go into production 
in January 2003. From this system, the ISTC data may be copied to one or 
several systems used for public access.  

An ISTC can be used as a search key for retrieving the bibliographic 
record of the work from the databases containing ISTC data. This record 
may contain ISTCs pointing to other works or other identifiers such as 
ISBNs, DOIs or SICIs identifying manifestations (books or articles) of 
the textual work. 

With the help of the registration agency element and the year code it is 
possible to locate the ISTC register (for instance, a traditional 
national bibliography database enriched with work metadata) of the 
Registration agency, which assigned the ISTC. Expanding the resolution 
of the ISTC-based URNs into these databases will bring two additional 
benefits. First, since the global ISTC register is maintained in batch 
mode it (and databases dependent on it) may not contain the newest ISTCs 
assigned by the registration authorities. Second, access to the systems 
containing global ISTC data may be for fee only, while the regional 
agencies may allow free access to their local ISTC registers. 

Typical users of the system will be authors and publishers seeking 
information about (published or non-published) works, librarians wishing 
to copy catalogue metadata related to a given work, and patrons who wish 
to track all manifestations of a work or expression related to it. 

3.4 Additional considerations

Since the number of ISTC resolution services will eventually be high 
(theoretical maximum 4096 + 1 "live" systems), encoding all services 
into the URN Resolution Discovery Service, and maintaining this data, 
may become a bottleneck. 

The ISTC system may become very large, as it is intended to cover all 
textual works, including novels, short stories and articles. Such a 
system may eventually become extremely popular. It is important that 
there will be multiple databases containing all or at least the most of 
the ISTC metadata in existence. 

4. Security Considerations

This document proposes means of encoding and using International 
Standard Text Work Codes within the URN framework. This document does 
not discuss resolution except at a generic level; thus questions of 
secure or authenticated resolution mechanisms in the ISTC registers are 
out of scope.  This text does not address means of validating the 
integrity or authenticating the source or provenance of URNs that 
contain ISTCs.  Issues regarding intellectual property rights associated 
with bibliographic data related to the ISTC or other work identifiers 
are also beyond the scope of this document, as are questions about 
rights to the databases that might be used to construct resolvers.

5. Namespace registration

URN Namespace ID Registration for the International Standard Text Work 
Code (ISTC)

Namespace ID:


ISTC will become an established acronym for International Standard Text 
Work Codes; giving this NID for any other system would cause a lot of 

Registration Information:

Version: 1
Date: 2002-07-03

Declared registrant of the namespace:

Name: International ISTC Agency / Albert Simmonds
Affiliation: OCLC Online Computer Library Center, Inc. 
Address: OCLC, 6565 Frantz Road, Dublin, OH 43017-3395, 

Declaration of syntactic structure:

Each ISTC contains four segments:

ISTC consists of four segments, all of which are required:

-	registration agency element;
-	year element;
-	work element;
-	check digit. 

When an ISTC is displayed in written form the letters ISTC shall precede 
it. The segments should be separated by hyphen or space. 

Registration agency element shall consist of three hexadecimal digits. 
The code (in the above example, 0A9) represents the Registration agency 
which assigned the ISTC. 

The year element (in the example, 2002) shall consist of the four digits 
representing the year in which the ISTC was allocated. 

The work element shall consist of eight hexadecimal digits. The work 
element shall be assigned by an ISTC Registration agency appointed by 
the Registration authority for ISO 21047. 

The check digit shall be calculated on a MOD 16-3 system defined in 
accordance with ISO 7064. 



ISTC codes can be generated and parsed by computer programs. 

Relevant ancillary documentation:

ISTC is an emerging ISO standard defined by ISO CD 21047 (revised 2002-
05-15). Draft International Standard version of ISTC will be published 
during summer 2002, and it is expected that ISTC will be approved as ISO 
standard in early 2003, after the DIS 6 months comment period. No major 
changes to the syntax of the ISTC or its maintenance organisation are 

Identifier uniqueness considerations:

ISTC codes will always be unique. 

Two or more different ISTCs may identify the same work if multiple 
registration agencies deal with the same resources, or if a single 
agency deals with the same work twice. The duplicate control algorithm 
in the ISTC Registration authority is intended to remove duplicates 
arriving from the agencies, and any agency should have sufficient 
control mechanism in place to avoid duplicate registration of works. 

Identifier persistence considerations:

Once assigned, ISTC will never change. The same ISTC will not be used 
again for another textual work.

Process of identifier assignment:

ISTCs will be assigned by the Registration agencies. Typically an author 
or his/her agent or a publisher will apply for an ISTC. It is also 
possible to generate ISTCs retrospectively for existing manifestations 
(published books and articles). This process has to be controlled well 
in order to avoid duplicate registration of works. One possibility is to 
generate work data in national bibliographic databases, and to limit the 
generation of work records to domestic works only. 

The Registration authority will govern the ISTC assignment process in 
the global level. The global ISTC Registry will enable duplicate control 
of the identified works. 

ISTC can - and should - be built via automated means. 

Process for identifier resolution:

Resolution will take place as defined in chapter 3.3. The first step is 
to check the ISTC register or another database containing all of ISTC 
metadata, or the most of it. If there is no match, it is possible to use 
the Registration agency element (and eventually the year element) as a 
hint for finding the Registration agency, which has assigned the ISTC, 
and the resolution service maintained by it. 

ISTCs will always resolve into the work metadata. Manifestations of the 
work (such as electronic versions of a book) may or may not be linked to 
the ISTC metadata. ISTC metadata may also contain links to related works 
and expressions. 

Rules for Lexical Equivalence:

Spaces and hyphens in the ISTC string are lexically equivalent. String 
"ISTC" in the beginning of the string must be neglected in the 

Conformance with URN Syntax:

ISTC consists of hexadecimal digits and it is therefore compliant to the 
requirements to the URN syntax as defined in [Moats]. 

Validation mechanism:

Validity of an ISTC string can be checked by modulus 16-3 check digit.



6. References

[Daigle et al.]: Daigle, L., van Gulik, D., Iannella, R. & Faltstrom, 
P.: URN Namespace Definition Mechanisms, RFC2611, June 1999.

[ISO] Information and documentation  International Standard Text Code 
(ISTC). ISO/CD 21047. May 2002. 

[Lynch] Lynch, C., Using Existing Bibliographic Identifiers as Uniform 
Resource Names, RFC 2288, February 1998

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

7. Authors' Address

   Juha Hakala
   Helsinki University Library - The National Library of Finland
   P.O. Box 26
   FIN-00014 Helsinki University


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