RFC 3187

Using International Standard Book Numbers as Uniform Resource Names

📅 published October 2001, from ietf

RFC 3187: Using International Standard Book Numbers as Uniform Resource Names 📚✨

PART 1 OF 2 🎀

  • Title: Using International Standard Book Numbers as Uniform Resource Names
  • Number: RFC 3187
  • Series: Network Working Group
  • Authors: J. Hakala (Helsinki University Library) and H. Walravens (The International ISBN Agency)
  • Category: Informational
  • Date: October 2001
  • Obsoletes / Updates: The header doesn't list anything it obsoletes or updates 🫶

Status of this Memo 💅

This memo is giving information for the Internet community. It is not an Internet standard of any kind, and it can be shared freely with no limits 🌸

Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract 🦋

So this document talks about how International Standard Book Numbers (ISBN) can fit into the URN (Uniform Resource Names) framework, using the URN syntax defined in RFC 2141. A lot of the discussion is built on the ideas from RFC 2288 🧚

1. Introduction ✨

Okay so, when the IETF URN working group was validating URNs, they agreed it was important to show that the current URN syntax could handle identifiers that already exist in well established namespaces. The bibliographic community has one of those systems, for naming things that show up in print and, more and more, in electronic form 📖💖

RFC 2288 [Lynch, et al.] looked into whether three identifiers (ISBN, ISSN and SICI) could work as URNs. This document goes deeper into ISBNs than RFC 2288 did, so it's giving detailed analysis bestie 🤓

There's a registration request for the Namespace Identifier (NID) "ISBN" for ISBNs in chapter 5 🎀

This document is part of a global joint venture of national libraries, which want to make it easier to identify electronic documents in general and to use URNs in particular. It was a co-operative project between the Helsinki University Library and The International ISBN Agency 🌈

In the examples below, we use the URN Namespace Identifier "ISBN" for ISBNs 💜

2. Identification vs. Resolution 🍓

As a general rule, ISBNs identify finite objects that are manageably sized. Some of those objects can still be big enough that splitting up their resolution into a hierarchical system makes sense 🧚

The materials an ISBN identifies might exist only in print or some other physical form, not electronically. In that case, the best a resolver can do is hand back bibliographic data from a national bibliography database. That includes info about where the physical item is kept in the national library's holdings 📚🙈

3. International Standard Book Numbers 💖

3.1 Overview 🌸

RFC 2288 [Lynch] explains the ISBN system like this. An ISBN identifies an edition of a monographic work, and it's defined by the standard NISO/ANSI/ISO 2108:1992 [ISO1] 💅

Basically, an ISBN is a ten-digit number, though the last digit can also be the letter "X", as described below. When printed, it's usually split into four parts of variable length, separated by hyphens. In order, those parts are:

  • a group identifier, which picks out a group of publishers based on national, geographic or some other criteria,
  • the publisher identifier,
  • the title identifier,
  • and a modulus 11 check digit, where X stands in for 10. ✨

The group and publisher assignments are managed so that you don't need the hyphens to split an ISBN into its parts without any mix-ups. Even so, an ISBN is normally written and shown with hyphens, so humans can spot the parts without having to know the number assignments for groups and publishers 🫶

Groups usually cover just one country, but sometimes one group is shared by several countries. For example, group "3" is used in Germany, Austria and the German-speaking parts of Switzerland 🇩🇪

Group "976" is used across the Caribbean community: Antigua, Bahamas, Barbados, Belize, Cayman Islands, Dominica, Grenada, Guyana, Jamaica, Montserrat, St. Kitts-Nevis, St. Lucia, St. Vincent and the Grenadines, Trinidad and Tobago, Virgin Islands (Br). Group "982" covers the South Pacific: Cook Islands, Fiji, Kiribati, Marshall Islands, Nauru, Niue, Solomon Islands, Tokelau, Tonga, Tuvalu; Vanuatu, Western Samoa 🌴

For every international group, the International ISBN Agency has given ranges of publisher identifiers to individual countries. You can find those ranges on the ISBN web site at http://www.isbn.spk-berlin.de/html/prefix.htm. The group identifiers are listed at http://www.isbn.spk-berlin.de/html/prefix/allpref.htm 💜

There are plans to extend ISBNs to 13 digits, so the system fits better with identifying electronic monographs. This so-called Bookland ISBN will be a traditional ISBN with the 978 or 979 EAN flag in front of it 🚀

3.2 Encoding Considerations and Lexical Equivalence 🦋

RFC 2288 [Lynch] says that putting ISBNs inside the URN framework doesn't cause any particular encoding problems, because every character that can show up in an ISBN is valid in the identifier segment of a URN. Percent-encoding, as described in [MOATS], is never needed 🙌

Example: URN:ISBN:0-395-36341-1 📖

For the ISBN namespace, a few extra equivalence rules make sense. Before comparing two ISBN URNs for equivalence, it's appropriate to remove all the hyphens, and to change any letter X to upper case 💅

3.3 Resolution of ISBN-based URNs 🧚

The existing ISBN structure works well for URN resolution. The group identifier can help the resolver with discovery. For instance, group identifier "951" means Finland. In that case, the Finnish national bibliographic database can resolve the URN either into bibliographic data or, if the resource is available on the Internet, into the document itself 🇫🇮

If a group identifier doesn't point to a single country but to a language area, there are two ways to find the right national bibliography. The first is to set up a cascade of URN resolution services. For example, you'd cascade the German national bibliography, then the Austrian national bibliography, then the Swiss national bibliography, in that order, into the DNS records that describe the resolution service for ISBNs starting with "3" 🌈

The second option is to put the publisher identifier ranges assigned by the International ISBN Agency into the DNS records. This beats cascading, because the correct resolution service can be found right away ⭐

Now here's the tea. In some exceptional cases, mostly in the US and the UK where international companies publish a big chunk of books, the group identifier might not be fully reliable. For example, some monographs published in New York by international publishing companies can get an ISBN with group identifier "3". That's technically correct when the publisher's headquarters or one of its offices is in Germany 💀

Info about a book like that won't be in the German national bibliography. Instead, it'll be found through the Library of Congress systems. The unfortunate part is that the resolver discovery service can't know which national bibliography is the right one 😭

As a fallback, a large union catalogue like WorldCat, maintained by OCLC (http://www.oclc.org), can complement the default services provided by national bibliographies 🫶

The problem above might be less serious than it looks. Some international publishers, Springer for example, send their whole production to the national library of their home country as legal deposit, no matter which country the book was published in. So everything Springer publishes in New York with group identifier "3" can be found in the German national bibliography ✨

On the flip side, when these companies also list their home base as a place of publication, the "home" national library requires the legal deposit 🎀

Because ISBNs are so intelligently structured, the group identifier or even the publisher identifier can be used as a "hint". Technically, publishers' own URN resolution services can also be built into the common structure. For instance, "951-0" is the unique ISBN publisher identifier of the largest publisher in Finland, Sanoma-WSOY. If they launch their own URN resolution services, requests for ISBNs starting with "951-0" would go to the publisher's server, and all other requests would go to the national bibliography 👑

3.4 Additional considerations 💜

The basic guidelines for assigning ISBNs to electronic resources are these:

  • Format and means of delivery don't matter when deciding whether a product needs an ISBN. If the content meets the requirement, it gets an ISBN, no matter what format the delivery system uses.
  • Each format of a digital publication should have a separate ISBN. 🙈

A new edition is normally defined by one of two criteria:

  • A change in the kind of packaging. For example, the hard cover edition, the paperback edition and the library-binding edition would each get a separate ISBN. The same goes for different formats of digital files.
  • A change in the text, leaving out packaging or minor changes like fixing a spelling error. Again, this applies whether the publication is printed or digital. 🧚

Even though these rules seem super clear, the way they're interpreted can vary. As [Lynch] points out, choosing whether to assign a new ISBN or reuse an existing one when publishing a revised printing of an edition, or even a revised edition of a work, is somewhat subjective. Practice varies from publisher to publisher, and the line between a revised printing and a new edition is itself somewhat subjective. Using ISBNs within the URN framework just reflects these existing practices. It's likely that an ISBN URN will often resolve to many instances of the work (many URLs) 📚

Publishers have also sometimes reused the same ISBN for another book. This is a fairly rare kind of human error, and it doesn't threaten or undermine the ISBN system as a whole. It also isn't a serious threat to the URN resolution service based on ISBNs. An error will only lead to two or more bibliographic records being retrieved from a national bibliographic database. Based on the information in those records, a user can pick the correct one from the result set 🌸

Most national bibliographies, and especially Books in Print, correct ISBN mistakes. The systems then provide cross references in the form "incorrect ISBN -> correct ISBN" 🫶

More details on how ISBNs are assigned can be found in section 5 (Namespace registration) below 🎀

Part 2 is coming next, bestie, so stay tuned 🧚💖

4. Security Considerations ✨

okay bestie, this section is SERIOUS but also kind of a vibe 🫶 this doc is only proposing how to encode ISBNs inside URNs 🦋. the resolution service is described super generically, so secure or authenticated resolution is NOT covered here 🙈. it also doesn't handle validating integrity or authenticating who the source or provenance of a URN with an ISBN is 💅. and the IP stuff tied to the objects the ISBNs identify is out of scope too, plus questions about rights to whatever databases get used to build resolvers 😭 that's a whole other era, not this doc 💜.

5. Namespace registration 🎀

okay so this part is the registration for the URN namespace ID for the International Standard Book Number 🍓. it basically explains how ISBNs can be used inside the URN framework ✨.

Namespace ID:

ISBN 🌸

the NID is the same as the internationally known acronym for the International Standard Book Number, and giving NID "ISBN" to any other identifier system would cause a lot of confusion 💀. don't be that person 🙅‍♀️.

Registration Information:

Version: 1 Date: 2001-01-25 Declared registrant of the namespace:

  • Name: Hartmut Walravens
  • E-mail: hartmut.walravens@sbb.spk-berlin.de
  • Affiliation: Director, The International ISBN Agency
  • Address: Staatsbibliothek zu Berlin - Preussischer Kulturbesitz - D-10772 Berlin, Germany

Declaration of syntactic structure:

an ISBN is a ten-digit number 🔢 (the last digit can actually be the letter X too, more on that below ✨). it's split into four variable-length parts, usually with hyphens when printed 🎀. in order, they are:

  1. a group identifier, which specifies a group of publishers based on national, geographic or some other criteria 🌍
  2. the publisher identifier 🏢
  3. the title identifier 📚
  4. and a modulus 11 check digit, using X instead of 10 ✨

example:

URN:ISBN:0-395-36341-1

Relevant ancillary documentation:

the ISBN is a unique machine-readable identification number that marks any edition of a book unambiguously 📖. it's defined in ISO Standard 2108 🧚. it's been around for 30 years and has totally revolutionised the international book trade 👑. 154 countries are officially ISBN members, and more are joining the system 🌈.

the admin is done on three levels 🫶:

International agency
Group agencies
Publisher levels

the International ISBN agency lives inside the State Library Berlin 🏛️. its main jobs are:

  • to promote, co-ordinate and supervise the world-wide use of the ISBN system 🌏
  • to approve the definition and structure of group agencies 📋
  • to allocate group identifiers to group agencies 🔖
  • to advise on the establishment and functioning of group agencies 💡
  • to advise group agencies on the allocation of international publisher identifiers 🎀
  • to publish the assigned group numbers and publishers prefixes in up-to-date form 📢

more info on ISBN usage is in the ISBN Users' Manual 📚. the 4th edition is available at http://www.isbn.spk-berlin.de/html/userman.htm 🔗.

Identifier uniqueness considerations:

an ISBN that has been assigned once should never be re-used 🙅‍♀️. BUT publishers do occasionally re-use the same number, ngl 🙈. from the point of view of the URN resolution system proposed here, this will typically cause retrieval of two bibliographic records 📚📚. the user can pick the correct publication using the data in the record, like the author or title 💅.

incorrect ISBNs get routinely corrected in national bibliographies and the Books in Print catalogue ✨.

Identifier persistence considerations:

the ISBN goes with a publication from its production onwards 🦋. it's persistent: an ISBN, once given (if correct), will never leave the publication 💖.

Identifier assignment process:

assignment of ISBNs is always controlled by ISBN group agencies 👑. these are often national and quite frequently located in national libraries 📚. publishers are usually given blocks of ISBNs, and they pick identifiers from those for their newly published items 🎁.

as pointed out earlier, even though everyone follows the common rules for using ISBNs, there's some variation between publishers in assignment 🙈. in practice these differences are so small that they don't threaten the usability of the ISBN system 🫶.

Identifier resolution process:

URNs based on ISBNs get resolved mainly through the national bibliography databases ✨. since ISBN group agencies are usually in national libraries, those databases cover almost every publication that has an ISBN 💅.

if a group identifier doesn't define a country but a language area, there may be many countries using the same group identifier 🌍. in that case, the International ISBN Agency has divided publisher identifiers into ranges assigned to each country within the group 🎀. the right resolution service can be found using the group identifier and publisher identifier info 🔍. alternatively, a cascade of national bibliographies can be defined 🫧.

resolution in national bibliography databases can be complemented by union catalogues, which hold a HUGE amount of bibliographic data (up to 42 million records) 🤯. this complementary service is only needed if the ISBN group identifier information is misleading, and that's not common 💅.

the International ISBN Agency maintains a list of publishers who've been assigned a publisher identifier within the ISBN system 📋. the publisher identifier may be used to let publisher-maintained resolution services join the URN resolution system for ISBN 🦋.

Rules for Lexical Equivalence:

for the ISBN namespace, some extra equivalence rules are appropriate 💜. before 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 ✨.

Conformance with URN Syntax:

embedding ISBNs in 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

Validation mechanism:

validity of an ISBN string can be checked with the modulus 11 check digit that's included in the ISBN 🔢. X is used instead of 10 ✨.

validity of ISBN assignments can be checked with the group agencies or directly with the publisher 🏢.

Scope:

Global 🌍.

6. References 📚

[Daigle] Daigle, L., van Gulik, D., Iannella, R. and P. Faltstrom,
         "URN Namespace Definition Mechanisms", RFC 2611, June 1999.

[Lynch]  Lynch, C., Preston, C. and R. Daniel, "Using Existing
         Bibliographic Identifiers as Uniform Resource Names", RFC
         2288, February 1998.

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

7. Authors' Addresses 🦋

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

EMail: juha.hakala@helsinki.fi


Hartmut Walravens
The International ISBN agency
Staatsbibliothek zu Berlin - Preussischer Kulturbesitz -
D-10772 Berlin
GERMANY

EMail: hartmut.walravens@sbb.spk-berlin.de
Copyright (C) The Internet Society (2001).  All Rights Reserved.

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works.  However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

## Acknowledgement ✨

Funding for the RFC Editor function is currently provided by the Internet Society 🫶.
📦 where this page comes from