IETF URNbis WG J. Hakala Internet-Draft The National Library of Finland Obsoletes: 3188 (if approved) A. Hoenes, Ed. Intended status: Standards Track TR-Sys Expires: June 25, 2011 December 22, 2010 Using National Bibliography Numbers as Uniform Resource Names draft-ietf-urnbis-rfc3188bis-nbn-urn-00 Abstract National Bibliography Numbers, NBNs, are widely used by the national libraries and other organizations in order to identify various resources such as monographs pre-dating the emergence of the ISBN system or still images. NBNs are applied to all kinds of resources that do not have an established identifier system of their own. Since 2001, there has been a URN (Uniform Resource Names) namespace for NBNs, and during 2001-2009 millions of URN-based unique and persistent NBNs have been assigned. The namespace registration was performed in RFC 3188 and applied to the NBNs known at that point. No URN:NBN resolution services existed at the time when the RFC was written. Since then, several countries including Finland, Germany, Italy, and the Netherlands have used URN:NBNs to identify electronic resources and to provide persistent links to them. To this end, these countries have established URN:NBN resolution services that supply URN - URL linking. This document replaces RFC 3188 and defines how NBNs can be supported within the URN framework. An updated namespace registration is included. Discussion This document is an outcome of work performed in 2009-2010 as a part of the project PersID (http://www.persid.org) and brought into the IETF; it formally introduces the RFC 3188bis work from PersID as a chartered work item of the URNbis WG. Comments are welcome and should be directed to the urn@ietf.org mailing list or the authors. Hakala & Hoenes Expires June 25, 2011 [Page 1] Internet-Draft NBN URN Namespace December 2010 Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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Hakala & Hoenes Expires June 25, 2011 [Page 2] Internet-Draft NBN URN Namespace December 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions used in this document . . . . . . . . . . . . . . 5 3. Fundamental Namespace and Community Considerations . . . . . . 5 3.1. The URN:NBN Namespace . . . . . . . . . . . . . . . . . . 5 3.2. Community Considerations for NBNs . . . . . . . . . . . . 6 4. National Bibliography Numbers (NBNs) . . . . . . . . . . . . . 7 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Encoding Considerations and Lexical Equivalence . . . . . 9 4.3. Resolution of NBN-based URNs . . . . . . . . . . . . . . . 11 4.4. Additional Considerations . . . . . . . . . . . . . . . . 12 4.5. URN Namespace ID Registration for the National Bibliography Number (NBN) . . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . . 19 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 8.1. Normative References . . . . . . . . . . . . . . . . . . . 19 8.2. Informative References . . . . . . . . . . . . . . . . . . 20 Appendix A. Draft Change Log . . . . . . . . . . . . . . . . . . 21 A.1. draft-hakala-rfc3188bis-nbn-urn-00 to draft-ietf-urnbis-*-00 . . . . . . . . . . . . . . . . . . 21 Hakala & Hoenes Expires June 25, 2011 [Page 3] Internet-Draft NBN URN Namespace December 2010 1. Introduction One of the basic permanent URI schemes (cf. RFC 3986 [RFC3986], [IANA-URI]) is 'URN' (Uniform Resource Name) as originally defined in RFC 2141 [RFC2141] and now being formally specified in RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn]. Any identifier, when used within the URN system, needs its own namespace. As of this writing, there are roughly 40 registered URN namespaces (see [IANA-URN]), one of which belongs to NBN, National Bibliography Number, as specified 2001 in RFC 3188 [RFC3188]. Currently URN:NBNs are in production use in several European countries including (in alphabetical order) Austria, Finland, Germany, Italy, the Netherlands, Norway, Sweden, and Switzerland. Several other countries in Europe and elsewhere are considering usage of them. URN:NBNs have been applied to, e.g., Web archives, digitized materials, and doctoral dissertations. As part of the validation process for the development of URNs back in the late 1990s, the IETF URN working group agreed that it was important to demonstrate that a 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 [RFC2288] investigated the feasibility of using three identifiers (ISBN, ISSN and SICI, see below) as URNs, with positive results; however, it did not formally register corresponding URN namespaces. This was in part due to the still evolving process to formalize criteria for namespace definition documents and registration, consolidated later in the IETF into RFC 3406 [RFC3406]. That RFC, in turn, is now being updated as well into RFC 3406bis [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg]. URN Namespaces have subsequently been registered for NBN (National Bibliography Number), ISBN (International Standard Book Number), and ISSN (International Serial Standard Number) in RFCs 3188 [RFC3188], 3187 [RFC3187], and 3044 [RFC3044], respectively. However, there is no registered namespace for SICI (Serial Item and Contribution Identifier), and no plans to make such registration, due to the lack of use of that standard. The ISBN namespace registration is being revised so that it covers both ISBN-10 and ISBN-13; [I-D.ietf-urnbis-rfc3187bis-isbn-urn]. The current ISSN registration still does not cover ISSN-L, defined in the new version of ISSN; the URNbis WG will provide an updated namespace registration in [RFC3044bis]. Hakala & Hoenes Expires June 25, 2011 [Page 4] Internet-Draft NBN URN Namespace December 2010 Please note that NBN differs from the other identifiers listed above because it is not a single identifier system and there is no standard describing NBN systems in use. The term "National Bibliography Number" encompasses all local identifier systems that the national libraries and their partner organizations use in addition to the more formally (and internationally) established identifiers. Historically, they were only applied in the national bibliographies to identify the resources catalogued into it. During the last 10 years, the NBN scope has been extended to cover a vast range of digital resources available via the Internet. Only a minority of these resources are catalogued in the national bibliographies or other bibliographical databases. Guidelines for using NBNs as URNs and the original namespace registration have been published in RFC 3188 [RFC3188]. The RFC at hand replaces RFC 3188; sections discussing the methods in which URN: NBNs can be resolved have been updated and the text is also made compliant with the stipulations of RFC 3406bis [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg], the successor of RFC 3406 [RFC3406], which previously had replaced RFC 2611 [RFC2611] that was applied in the initial registration. 2. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. NBN refers to any National Bibliography Number identifier system used by the national libraries and other institutions using the system with the national library's permission. 3. Fundamental Namespace and Community Considerations 3.1. The URN:NBN Namespace NBNs identify objects covered by legal requirements on national libraries and similar institutions to preserve the cultural inheritage of their constituents. They are predominantly used for objects that have not been assigned other, more specific, standard identifiers that could be used to identfy them in catalogues and other collections of metadata. Therefore, to the same extent as NBNs are used to close gaps between existing, more universal, but also more specific, identifier systems (like ISBN and ISSN), a dedicated URN namespace is needed to map these identifiers into the URN system and thus make them actionable for URN resolution systems. Hakala & Hoenes Expires June 25, 2011 [Page 5] Internet-Draft NBN URN Namespace December 2010 Section 4 below, and there in particular Section 4.1, presents a detailed overview of the structure of the NBN namespace, related institutions, and the identifier assignment principles used. 3.2. Community Considerations for NBNs National libraries are the key organizations providing persistent URN resolution services for resources identified with NBNs, independent of their form. National libraries may however allow other organizations such as university libraries or governmental organizations to assign NBNs to their resources. In such case the national library will co-ordinate the use of NBNs and support the NBN users in guaranteeing the persistence of these resources and resolution. These other organizations may establish their own resolution services or they may use the infrastructure provided by the national library. NBNs identify finite objects, but sometimes these objects might be so large or complex that identification of fragments is appropriate (in addition to identification of the resource itself). The materials identified by an NBN will often be digital, but they may also exist only in printed or other physical form. In such a case, the URN:NBN resolver should nevertheless be able to supply, e.g., a description of the resource, possibly including the address where the resource is available. National bibliography numbers enable the national libraries and organizations which liaise with them to uniquely identify resources and provide persistent links to the resource accessible in the Internet. Since most digital documents held in national libraries' digital collections are not eligible for other, more formal identifiers such as ISBN, NBNs are a valuable asset for the community. A proof of this are the millions of URN:NBNs that have been allocated since the NBN namespace was registered, and the operational services that have been built, using these identifiers and resolver applications. For library users, URN-based identification and resolution services mean more efficient and reliable access to resources. No special tools are needed for this; Web browsers are sufficient. The users may also be able to acquire URN:NBNs to their own works such as a university thesis. Section 4 below, and in particular Section 4.3 therein, presents a detailed overview of the application of the URN:NBN namespace and the principles, and systems used, for the resolution of NBN-based URNs. Hakala & Hoenes Expires June 25, 2011 [Page 6] Internet-Draft NBN URN Namespace December 2010 4. National Bibliography Numbers (NBNs) 4.1. Overview National Bibliography Number (NBN) is a generic name referring to a group of identifier systems administered by the national libraries and institutions authorized by them. The NBN assignment is typically performed by the organization hosting the resource. These organizations (national libraries and institutions in liaison with them) are usually committed to preserving their collections for a long time -- at least decades, and possibly centuries. National libraries give NBNs to resources belonging to the (legal) deposit collections which by default will be kept as long as possible, but not to resources considered ephemeral. Each national library uses its own NBNs independently of other national libraries; there is no global authority that controls NBN usage. For this reason, NBNs as such are unique only on a national level. When used as URNs, NBN strings MUST be augmented with a controlled prefix such as the ISO 3166-1 alpha-2 two-letter country code. These prefixes guarantee uniqueness of the NBN-based URNs on the global scale [Iso3166MA]. NBNs have traditionally been given to documents that do not have a formal (standard) identifier, but are catalogued to the national bibliography. Examples of this include books that predate the introduction of the ISBN in the 1970s, or modern books that for some reason have not received an ISBN. NBNs can be seen as a fall-back mechanism: if no other, standards-based identifier such as an ISBN can be given, an NBN is assigned. URNs may also be used in universities' open repositories when a resource already has another identifier -- for instance, a Handle required by the open archive software, or a DOI (Digital Object Identifier) -- that can only be resolved in a publisher's (or third party's) resolution service. Such persistent identifier cannot be used to provide linking to the open repository or legal deposit collection. URN:NBN-based resolution can deliver that, and may also be extended to include access to other repositories holding the same resource. In principle, NBNs enable identification of any kind of resource, such as still images published in periodical articles, or short stories and poems published in book form or in the Web. Local policies may limit the NBN usage to for instance documents stored permanently in the national library's collections. Following the initial registration of a URN namespace for NBN, several countries broadened the scope of NBN assignment significantly to cover broader scope of their digital materials. Hakala & Hoenes Expires June 25, 2011 [Page 7] Internet-Draft NBN URN Namespace December 2010 Some national libraries (e.g., Finland, Norway, Sweden) have established Web-based URN generators, which enable authors and publishers to fetch NBN-based URNs for their network resources. There are also applications, used for instance in digitization processes, that assign NBNs automatically to resources or even their component parts such as still images published in monographs or serials. Within the limitations set by RFC 2141[bis], this document, and other relevant RFCs, both syntax and scope of local NBNs can be decided by each national library independently. Historically, NBNs have consisted of one or more letters and/or digits. For instance, (Finnish) NBN for the Romanian translation of the Finnish classic "Seven Brothers" published in 1957 is f568471. URN strings can contain encoded UNICODE characters, as specified in the declaration of syntactic structure, and there are no length limitations. Therefore, literally billions of NBNs can be allocated, which makes them suitable for, e.g., naming of Web documents. In Italy a novel hierarchical distributed architecture for NBN assignment has been designed, in order to eliminate the single-point- of-error risks of a centralised system and to reduce the costs of managing a resolution service based on persistent identifiers. The Central National Library in Florence manages the national domain NBN:IT and the national URN resolution service that contains every URN:NBN assigned in Italy. The library has supplied URN:NBN:IT sub- domains to trusted institutions and bodies such as universities that are responsible for digital collections and routinely manage digital resources, for instance via creating and updating metadata on these resources, including location (URL) information. All these institutions have their own resolution services, but the URN - URL mappings in them are periodically harvested to the national resolution service using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH; see (). Harvesting the data to the central node enables distributed service. The central node can serve the users when the local node is not functional. This architecture increases the robustness of the network via duplication of resolution services and enables peer-to- peer resolution between the second-level institutions. Moreover, it is possible to add yet another layer to the network by creating an international node, which shall contain all the data from the national nodes. Such international service may also be created by building a virtual union resolver that uses all the national nodes. Hakala & Hoenes Expires June 25, 2011 [Page 8] Internet-Draft NBN URN Namespace December 2010 The PersID project is implementing such a system at the European level. 4.2. Encoding Considerations and Lexical Equivalence Embedding NBNs within the URN framework initially did not present any particular encoding problems, since the ASCII characters utilized in traditional NBN systems belonged to the URN character set. Machine generated NBNs may be more demanding; if necessary, NBNs must be translated into canonical form as specified in RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn]. When an NBN is used as a URN, the namespace-specific string must consist of three parts: o a prefix, consisting of either a two-letter ISO 3166-1 country code or another registered string, o a delimiting character that is either hyphen (-) or colon (:), and o the NBN string. ISO 3166-1 country codes and other registered prefix strings are case-insensitive. The NBN string may be case sensitive. Different delimiting characters are not lexically equivalent. A hyphen MUST be used for separating the prefix and the NBN string. A colon MAY be used as the delimiting character if and only if a country code-based NBN namespace is split further into smaller sub- namespaces. If there are several national libraries in one country, these libraries can divide the national namespace between themselves using this method. A national library MAY also assign to trusted organization(s) such as a university or a government institution its own NBN sub-namespace. For instance, the national library of Finland has given Statistics Finland () a sub-namespace "st" (i.e., urn:nbn:fi:st). These trusted organizations must follow the general rules of the NBN usage provided by the national library, and take care of the long-term preservation of the identified resources in order to guarantee persistence. Sub-namespace identifier strings are case-insensitive. Hakala & Hoenes Expires June 25, 2011 [Page 9] Internet-Draft NBN URN Namespace December 2010 Non-ISO 3166-1 alpha-2 prefixes, if used, MUST be registered on the global level. The U.S. Library of Congress maintains the central register of assigned non-ISO 3166-1 prefix strings together with the name and contact information of the registrant. Each prefix MUST have one and only one user organization, which is responsible for maintaining the delegated sub-namespace according to the general rules set out in this document. Since the setup of that registry, and up to the time of this writing, no such prefixes have been registered, and it is expected that demand will remain low. Therefore, no more complicated rules (for instance for a hierarchical structure of such prefixes), are specified here. For this unlikely case of unexpected future needs, a revision of this document would be needed to accommodate that. [[ Note: If the NBN community does not see a need to maintain this -- so far unused -- option for prefixes not based on ISO 3166-1, it could be dropped without breaking backwards compatibility. Another option to consider would be migrating the registry to IANA if that would be preferred by the Library of Congress. ]] Sub-namespace codes beneath a country-code-based namespace MUST be registered on the national level by the national library that assigned the code. The national register of these codes SHOULD be made available online. All two-letter prefixes are reserved for existing and possible future ISO country codes (or for private use) [Iso3166MA] and MUST NOT be used as non-ISO country-code prefixes. If there are several national libraries in one country that use the same country code as a shared prefix, they need to agree on how to divide the namespace. They may either share one namespace but agree on how to avoid assigning duplicate identifiers, or they may split the namespace into library- specific sub-namespaces. Models (indicated linebreak inserted for readability): URN:NBN:- URN:NBN::-\ URN:NBN:- Examples (using actually assigned NBNs): Hakala & Hoenes Expires June 25, 2011 [Page 10] Internet-Draft NBN URN Namespace December 2010 URN:NBN:fi-fe201003181510 urn:nbn:ch:bel-9039 urn:nbn:se:uu:diva-3475 urn:nbn:hu-3006 From the libraries' point of view, one of the key benefits of using URNs and other persistent identifiers is that there is only one location -- the resolution service -- where the linking infomation has to be maintained. If bibliographic records in libraries' on-line public access catalogues (OPACs) contain URLs, then each record must be modified whenever the URL changes. This may mean hundreds of changes for a popular resource. With URNs, only the URN - URL linking in the mapping table of the resolution servicem needs to be kept up-to-date. All links in the bibliographic records point to the resolution service where the URN is translated to one or more URL(s). 4.3. Resolution of NBN-based URNs [[ Editorial Note: the text below needs to be revisited once the perspective of the list of URN services in RFC 2483 has been discussed and resolved by the WG. ]] URNs can be used to provide various services. RFC 2483 [RFC2483] gives a few examples, such as retrieving a single URL or all URLs applying to the resource. The constant development of digital library applications has widened the scope of the services needed, which has meant that RFC 2483 is becoming more outdated all the time. Resolution services available may vary from one URN resolver to the next, depending on the technical implementation of the resolver and the target system contacted. Please note that services MUST NOT be hard coded into the URN itself when the identifier is assigned. Eventually, URN:NBNs will be resolved with the help of a resolver discovery service (RDS). No such system has been installed yet in the Internet infrastructure. Therefore, URN:NBNs should be embedded in HTTP URIs in order to make them actionable in the present Internet. In these HTTP URIs, the authority part must point to the appropriate URN resolution service. In Finland, the address of the national URN resolver is . Thus the HTTP URI for the URN in the example is . This URL in turn resolves to the actual address of the thesis, which as of this writing (2010-03-27) was . Hakala & Hoenes Expires June 25, 2011 [Page 11] Internet-Draft NBN URN Namespace December 2010 The country code-based prefix part of the URN namespace-specific string will provide a guide to finding the correct national resolution service for URN:NBNs from the resolver discovery service when it is established. If there are multiple URN:NBN resolvers in the country, there are two possible approaches for making sure that RDS will work. All URN:NBNs mappings can be harvested to the national node (the Italian approach). The other approach is to make the RDS aware of all the URN:NBN resolution services, and specify in the RDS which parts of the national URN:NBN namespace they are capable of serving. URN:NBN - URL mappings maintained nationally can be harvested using, e.g., OAI-PMH from abroad to other national and international URN resolvers. This makes it possible to improve the reliability of the system; if the Finnish national resolver node does not respond, its URN - URL mappings may be available at other resolvers. Persistence of any resolution service is not only a technical issue, but also an organizational and legal one. National libraries are in ideal position to provide persistent resolution services, since most of them maintain (legal) deposit collections, in which domestic publications shall be preserved for future generations. Increasingly these collection contain also digital resources. 4.4. Additional Considerations Guidelines adopted and promoted by each national library define when different manifestations of a work should be assigned the same or differing NBNs. But some simple guidelines should be followed by all users of the namespace. Manifestations with significantly different semantic content -- following for instance a migration that failed to retain all content -- must not have the same NBN. Manifestations that have the same content but different look and feel, or manifestations that look (almost) identical but have significant technical differences (such as the same text document as Word 2003 file and OOXML file, or the same image as uncompressed TIFF and JPEG 2000) should not have the same NBN. If there are several copies of the file hosted by one organization, each copy must have the same NBN. If the NBN is based on a checksum (such as MD5, see RFC 1321 [RFC1321]), the resources that are identical at the bit level will receive the same NBN. Dissimilar resources may in theory get the same checksum; with a reliable message digest algorithm such probability is however very small. The rules governing the usage of NBNs are local and usually less strict than those specifying the usage of ISBNs and other standard identifiers. As long as the NBNs were assigned only in the national libraries, the identifier use was however well co-ordinated in Hakala & Hoenes Expires June 25, 2011 [Page 12] Internet-Draft NBN URN Namespace December 2010 practice. Now, following significant broadening in the scope of the NBN to cover Web resources, NBN assignment is less tightly controlled. Works may have several manifestations that may be almost identical. For instance, a single photo can published in many electronic newspapers in different countries. Since there is no standard identifier for still images, such a photo is likely to receive multiple NBN, one in each national web archive. Printed materials will also cause problems when dititized. If two organizations are digitizing the same resources and use NBNs for identification of these resources, the result will be duplicate NBN assignment since NBNs as a rule have national scope, and these organizations may not be aware of each other. If the metadata describing the resource is harvested into a common service, and the bibliographic records are similar enough to be merged, the user may see two NBNs and HTTP URIs pointing to two different resolution services and physical copies of the same resource. If the two copies had the same identifier such as an ISBN, there would still be two HTTP URIs providing access to different physical copies of the resource since the locations of the resolution services will differ. If the same resource -- for instance, a master's thesis published by two universities -- is held in two repositories located in different NBN-sub-namespaces within one national namespace, these copies may also receive different NBNs especially if there is no easy way of checking if the resource has already been identified somewhere. In this case, duplication may be revealed in the national level when the metadata records of the two copies are compared. In such case, like in the previous example, both URN:NBNs are equally valid. 4.5. URN Namespace ID Registration for the National Bibliography Number (NBN) This registration describes how National Bibliography Numbers (NBNs) can be supported within the URN framework. [[ RFC Editor: please replace "XXXX" in all instances of "RFC XXXX" below by the RFC number assigned to this document. ]] Namespace ID: NBN This Namespace ID was formally assigned to the National Bibliography Number in October 2001 when the namespace was registered officially. Utilization of URN:NBNs started in demonstrator systems in 1998; since then, millions of URN:NBNs have been assigned. The number of users of the namespace has grown in two ways: new national libraries have started using NBNs, and some national libraries already using the system have formed new liaisons. Hakala & Hoenes Expires June 25, 2011 [Page 13] Internet-Draft NBN URN Namespace December 2010 Registration Information: Version: 4 Date: 2010-12-22 Declared registrant of the namespace: Name: Mr. Juha Hakala Affiliation: Senior Adviser, The National Library of Finland Email: juha.hakala@helsinki.fi Postal: P.O.Box 15, 00014 Helsinki University, Finland Web URL: http://www.nationallibrary.fi/ The National Library of Finland registered the namespace on behalf of the Conference of the European National Librarians (CENL) and Conference of Directors of National Libraries (CDNL), which have both made a commitment in 1998 to foster the use of URNs. The NBN namespace is available for free for all national libraries in the world. The national libraries may allow other organizations use the namespace for free or for a fee. Declaration of syntactic structure of NSS part: The namespace-specific string (NSS) will consist of three parts: a prefix, consisting of either an ISO 3166-1 alpha-2 country code or other registered string and sub-namespace codes, delimiting characters (colon (:) and hyphen (-)), and an NBN string assigned by the national library or sub-delegated authority. Formal declaration of the NSS, using ABNF [RFC5234]: Hakala & Hoenes Expires June 25, 2011 [Page 14] Internet-Draft NBN URN Namespace December 2010 nbn_nss = prefix "-" nbn_string prefix = cc_prefix / reg_prefix ; these prefixes are case-insensitive cc_prefix = iso_cc *( ":" subspc ) iso_cc = 2ALPHA ; country code as assigned by ISO 3166, part 1 -- ; identifies the national library ; to which the branch is delegated subspc = 1*(ALPHA / DIGIT) ; as assigned by the respective national library reg_prefix = 3*(ALPHA / DIGIT) ; as assigned by the Library of Congress -- ; identifies a trusted third party ; to which the branch is delegated nbn_string = ; MUST adhere to RFC 3986 syntax; ; parsers must regard nbn_strings as case-sensitive Colon may be used as a delimiting character only within the prefix, between ISO 3166-1 country code and sub-namespace code(s), which split the national namespace into smaller parts. Dividing non-ISO 3166-based namespaces further with sub-namespace codes MUST NOT be done. Whereas all prefixes are regarded as case-insensitive, NBN-strings MAY be case-insensitive at the preference of the assigning authority; parsers therefore MUST treat these as case-sensitive; any case mapping needed to introduce case-insensitivity MUST be implemented in the responsible resolution system. Hyphen MUST be used as the delimiting character between the prefix and the NBN string. Within the NBN string, hyphen MAY be used for separating different sections of the identifier from one another. Non-ISO prefixes used instead of the ISO country code must be registered. A global registry, maintained by the Library of Congress, has beeen created and made available via the Web. Contact information: . All two-letter codes are reserved for existing and possible future ISO country codes and MUST NOT be used as non-ISO prefixes. Hakala & Hoenes Expires June 25, 2011 [Page 15] Internet-Draft NBN URN Namespace December 2010 Sub-namespace codes MUST be registered on the national level by the national library that assigned the code. The list of such codes SHOULD be available via the Web. Models (indicated linebreak inserted for readability): URN:NBN:- URN:NBN:-\ URN:NBN:- Example: urn:nbn:de:gbv:089-3321752945 Relevant ancillary documentation: National Bibliography Number (NBN) is a generic name referring to a group of identifier systems used by the national libraries and other organizations for identification of deposited publications and other resources that lack a 'canonical' identifier, or to descriptive metadata (cataloguing) that describes the resources. Each national library uses its own NBN system independently of other national libraries; there is neither a general standard defining NBN syntax nor a global authority to control the use of these identifier systems. Each national library decides locally which resources shall receive NBNs. These identifiers have traditionally been assigned to documents that do not have a publisher-assigned identifier, but are nevertheless catalogued to the national bibliography. Typically identification of grey publications have largely been dependent on NBNs. With the introduction of the Internet and URN: NBN namespace in 1998, the scope of NBN assignment has been extended to a broad spectrum of Internet resources including, e.g., harvested Web pages. Some national libraries (Finland, Norway, Sweden) have established Web-based URN generators that enable authors and publishers to fetch NBN-based URNs for the resources they publish in the Web. The most significant group of publications to which NBNs have been applied are doctoral theses. The syntax of NBNs is decided by each national library independently. Historically, NBNs used in national bibliographies contained only characters that belong to the URN character set. Hakala & Hoenes Expires June 25, 2011 [Page 16] Internet-Draft NBN URN Namespace December 2010 Following the expansion of NBN scope and semi- and fully automated NBN assignment processes, some NBNs may contain characters that must be translated into canonical form according to the specifications in RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn]. Conformance with URN syntax: Traditional NBNs (those applied in the national bibliographies) consisted of ASCII 7-bit letters and digits (a-z and 0-9). For instance, the NBN of the first Hungarian translation of the Finnish national epos Kalevala is f20043425. The book was published in 1853 and therefore does not have an ISBN. Machine- generated NBNs must follow the stipulations of RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn]. [[ Editorial Note: Need to discuss new specification requirements from the RFC 2141bis draft! ]] Rules for lexical equivalence of NSS part: Two URN:NBNs are lexically equivalent if they are octet-by-octet equal after the following (conceptional) preprocessing: 1. normalize the case of the leading "urn:" token 2. normalize the case of the NID 3. normalize the case of the NSS prefix 4. normalize the case of any percent-encoding Note: The case used in the normalization steps is a local matter; implementations can normalize to lower or upper case as they see fit, they only need to do it consistently. Identifier uniqueness and persistence considerations: NBN strings assigned by two national libraries may be identical. In order to guarantee global uniqueness of NBN-based URNs, therefore a controlled prefix is present in the namespace specific string. These NBNs, once given to the resource, will be persistent. Persistence of the resources themselves will be guaranteed by the national libraries as a part of their legal deposit activities. This applies to publications and Web resources only; long-term preservation of other resources such as governmental documents will be dependent on other actors like national archives. An NBN, once it has been assigned, must never be re-used for another resource. At the national level, libraries may utilise different policies Hakala & Hoenes Expires June 25, 2011 [Page 17] Internet-Draft NBN URN Namespace December 2010 for guaranteeing uniqueness of NBNs. They may be assigned sequentially by programs (URN generators) in order to avoid human mistakes. It is also possible to use checksums such as SHA-1 or MD5 as NBN. Process of identifier assignment: Assignment of NBN-based URNs MUST be controlled on national level by the national library / national libraries. Although the basic principles are the same, there are differences in scope; for instance in the Netherlands URN:NBNs are used -- among other things -- to identify scientific articles stored in the national library's long-term preservation system. The National Library of Finland, on the other hand, is using URNs extensively to identify and provide access to the digitized content. There are also organizations that use NBN-based URNs to identify data sets. The common denominator, however, is that the identified resources themselves are persistent. National libraries may choose different strategies in assigning NBN-based URNs, and different approaches have varying levels of control with respect to the persistence of the documents. Manual URN assignment by the library personnel only provides the best possible control, especially if this is done traditionally, that is, only when the document is catalogued into the national bibliography. Usually the scope of URN:NBN is much broader than this; NBNs may for instance be automatically generated for each archived resource by a long-term preservation system. From control point of view, the most liberal approach is a URN generator which builds URNs for everyone, with no guarantee that the resource identified will be preserved or accessible. Every national library must decide the degree of freedom it allows to the URN:NBN users. Usage rules may of course vary from one sub- namespace to the next. As of yet there are no international guidelines for NBN use beyond what has been stipulated above, but more sttringent rules may be developed in the future. Process for identifier resolution: See Section 4.3 of RFC XXXX. Validation mechanism: None specified on the global level (beyond a routine check of those characters that require special encoding when employed in URIs). A national library may use NBNs that contain a checksum and can therefore be validated, but as of this writing there are no NBNs which incorporate such checksum. Hakala & Hoenes Expires June 25, 2011 [Page 18] Internet-Draft NBN URN Namespace December 2010 Scope: NBN is an umbrella referring to identifier systems used for identification of diverse publications and other resources in the national libraries and their partner organizations. 5. Security Considerations This document proposes means of encoding NBNs within the URN framework. A URN resolution service for NBN-based URNs is depicted, but only at a fairly generic level; thus, questions of secure or authenticated resolution mechanisms and authentication of users are out of scope of this document. It does not deal with means of validating the integrity or authenticating the source or provenance of URNs that contain NBNs. Issues regarding intellectual property rights associated with objects identified by the NBNs are also beyond the scope of this document, as are questions about rights to the databases that might be used to construct resolution services. 6. IANA Considerations IANA is asked to update the existing registration of the Formal URN Namespace 'NBN' using the template given above in Section 4.5. 7. Acknowledgements This document is an outcome of work performed in 2009-2010 as a part of the project PersID (http://www.persid.org) that aims at revising the basic URN RFCs, in order to bring them in alignment with the current URI Standard (STD 63, RFC 3986), ABNF, and IANA guidelines, and to establish a modern URN resolution system for bibliographic identifiers. This work has been brought to the IETF and has lead to the establishment of the URNbis working group in the Applications Area. The author wishes to thank his colleagues in the PersID project for their support. Your name could go here ... 8. References 8.1. Normative References [I-D.ietf-urnbis-rfc2141bis-urn] Hoenes, A., "Uniform Resource Name (URN) Syntax", draft-ietf-urnbis-rfc2141bis-urn-00 (work in progress), November 2010. Hakala & Hoenes Expires June 25, 2011 [Page 19] Internet-Draft NBN URN Namespace December 2010 [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg] Hoenes, A., "Uniform Resource Name (URN) Namespace Definition Mechanisms", draft-ietf-urnbis-rfc3406bis-urn-ns-reg-00 (work in progress), December 2010. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. 8.2. Informative References [I-D.ietf-urnbis-rfc3187bis-isbn-urn] Huttunen, M., Hakala, J., and A. Hoenes, "Using International Standard Book Numbers as Uniform Resource Names", draft-ietf-urnbis-rfc3187bis-isbn-urn-00 (work in progress), December 2010. [IANA-URI] IANA, "URI Schemes Registry", . [IANA-URN] IANA, "URN Namespace Registry", . [Iso3166MA] ISO, "ISO Maintenance agency for ISO 3166 country codes", . [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. [RFC2288] Lynch, C., Preston, C., and R. Jr, "Using Existing Bibliographic Identifiers as Uniform Resource Names", RFC 2288, February 1998. [RFC2483] Mealling, M. and R. Daniel, "URI Resolution Services Necessary for URN Resolution", RFC 2483, January 1999. [RFC2611] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom, "URN Namespace Definition Mechanisms", BCP 33, RFC 2611, June 1999. Hakala & Hoenes Expires June 25, 2011 [Page 20] Internet-Draft NBN URN Namespace December 2010 [RFC3044] Rozenfeld, S., "Using The ISSN (International Serial Standard Number) as URN (Uniform Resource Names) within an ISSN-URN Namespace", RFC 3044, January 2001. [RFC3187] Hakala, J. and H. Walravens, "Using International Standard Book Numbers as Uniform Resource Names", RFC 3187, October 2001. [RFC3188] Hakala, J., "Using National Bibliography Numbers as Uniform Resource Names", RFC 3188, October 2001. [RFC3406] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom, "Uniform Resource Names (URN) Namespace Definition Mechanisms", BCP 66, RFC 3406, October 2002. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. Appendix A. Draft Change Log [[ RFC-Editor: Whole section to be deleted before RFC publication. ]] A.1. draft-hakala-rfc3188bis-nbn-urn-00 to draft-ietf-urnbis-*-00 - formal updates for a WG draft; no more "Updates: 2288"; - introduced references to other URNbis WG documents; - changes based on review by Tommi Jauhiainen; - Sect. 3 restructured into namespace and community considerations; - old Sect. 7 incorporated in new Sect. 3.1; - Security Considerations: old Section 4.5 merged into Section 5; - added guidelines for when two manifestations of the same work should get different URN:NBNs; - clarified role of ISO 3166/MA for ISO 3166-1 country codes; - clarified role of non-ISO prefix registry maintaind by the LoC; - resolved inconsistency in lexical equivalence rules: as already specified for ISO alpha-2 country-codes, and in accordance with established practice, the whole NBN prefix is now declared case- insensitive; - registration template adapted to rfc3406bis [-00]; - numerous editorial fixes and enhancements. Hakala & Hoenes Expires June 25, 2011 [Page 21] Internet-Draft NBN URN Namespace December 2010 Authors' Addresses Juha Hakala The National Library of Finland P.O. Box 15 Helsinki, Helsinki University FIN-00014 Finland Email: juha.hakala@helsinki.fi Alfred Hoenes (editor) TR-Sys Gerlinger Str. 12 Ditzingen D-71254 Germany Email: ah@TR-Sys.de Hakala & Hoenes Expires June 25, 2011 [Page 22]