"Building a network of expertise for Digital Library Services, Standardisation and Metadata:
Sub-project EPICUR - Enhancement of Persistent Identifier Services - a Comprehensive Method for Unequivocal Resource Identification"

Table of Contents

Project Partners
I. Objectives
I.1 General Project Objectives, accompanying funding policy
I.2 Scientific and technical project objectives
I.2.1 General Outline
I.2.1.1 Uniform Resource Name (URN) scope
I.2.1.2 Digital Object Identifier (DOI) scope
I.2.1.3 Complementary use of Digital Object Identifiers (DOI) and Uniform Resource Names (URN)
I.2.1.4 Persistent Identifier (PI) products
I.2.2 Implementation at Die Deutsche Bibliothek
I.2.2.1 Uniform Resource Name (URN) scope
I.2.2.2 Digital Object Identifier (DOI) scope
I.2.2.3 Complementary use of Digital Object Identifiers and Uniform Resource Names
I.2.2.4 Persistent Identifier (PI) products
II. State of the art in science and technology; related scientific research
III. Comprehensive description of working plan
III.1 Resource planning and management at Die Deutsche Bibliothek
III.1.1 International co-operation
III.1.2 National co-operation
III.1.3 Uniform Resource Name (URN) scope
III.1.4 Digital Object Identifier (DOI) scope
III.2 Content related scientific working plan
III.2.1 Conception and project management
III.2.2 Technical implementation plan
III.3 Project related resource planning, deliverables (time line)
IV. Working packages / national and international co-operation
V. Operating plan
VI. Funding requirements
Index of abbreviations

Project partners

Kathrin SchroederProject manager Die Deutsche Bibliothekschroeder@dbf.ddb.de

Tel: 069-1525-1480
Fax:        -1799

N.N.BAT IIa   


Die Deutsche Bibliothek, Deutsche Bibliothek Frankfurt am Main, Adickesallee 1, 60322 Frankfurt am Main, Germany

I. Objectives

I.1 General project objectives, accompanying funding policy

The increasing demand in the number of online publications in recent years requires the application of unique identification systems on the internet instead of unstable Uniform Resource Locators (URLs) for efficient use of network publications. The introduction of Persistent Identifiers (PIs) compensates disadvantages of URLs, guarantees persistent availability, and thus enables permanent referencing of online resources. URLs are replaced by PIs as identifiers and document access method; then, the PIs are resolved in the assigned URLs via intermediate mechanism resolving).

Examples of PI systems are DOI (Digital Object Identifier)[1], mainly applied by publishers in eCommerce and Content Management, and URN (Uniform Resource Name) [2] in the non-commercial sector. The two systems are based on almost opposite yet mutually complementary conditions.

URN is a standard for resource addressing and also a specific Uniform-Resource-Identifier-(URI) scheme [3], institutionally committed to persistent, location-independent identification of online resources. URNs are designed to keep the cost for providing Gateways and using URNs as low as possible - comparable to existing namespaces like e.g. URLs. Therefore, integration of existing or already applied namespaces or numeric systems into the URN scheme and common protocols like e.g. HTTP Hypertext Transfer Protocol) or schemes like e.g. URLs, is standardised [4].

DOI is a system for identifying and exchanging any entity of intellectual property. Additionally, DOI provides technical and organisational general set-up to manage digital objects and connect producers or information providers with their customers. Thus, with DOIs, it is possible to develop and automate services for electronic resources which are access controlled due to copyrights, licensing or other commercial reasons. DOI is a technical implementation of the CNRI-(Corporation for National Research Initiatives) Handle System [5], applying the notation "DOI" instead of "handle" to describe the identifier.

DOI is an elaborate, but self-contained technical system for identification and administration of resources. URNs, with their open technical approach, offer potential for universal, global resolving. Through adaptation to individual scenarios, some PI services have established themselves in both systems [6]. Yet, there is still a common demand for action and further development regarding introduction of PIs, establishing procedures, and technical solutions for complementary application of DOIs and URNs, further technical development of PI services, and creating organisational network of expertise for URNs on national and international levels. This is an essential result of the CARMEN-AP4 project [7]: "Development in this area is still in motion, consequently, despite existing procedures, co-operation and co-design in developing standards and procedures oriented to demands and requirements of the participants, is necessary."[8]

In the framework of the CARMEN-AP4 project, Die Deutsche Bibliothek has implemented a co-operation oriented, distributed URN management. Positive response [9] and broad acceptance [10] reflect the need of expanding organisational and technical features of the existing URN service of Die Deutsche Bibliothek. The technical expansion is aiming at developing and implementing a secure, efficient technical infrastructure for a PI service based on the CARMEN-AP4 prototype with additional functions. Furthermore, framework conditions on national level shall be created, enabling and supporting decentralised PI services providing connection to a globally managed URN resolving service. In organisational terms, co-operation with pertinent organisations and companies shall provide secure application of PIs as standard numbers e.g. in library presentation formats and other products. On international level, Die Deutsche Bibliothek, in co-operation with the National Library of Helsinki, aims at bundling information by establishing a "URN Information Center" and a central clearing office for URN information, based on the decision made at the CoBRA+ (Computerised Bibliographic Record Actions) meeting in July 2002. On top of this, international interest representation within the scope of URN shall be initiated.

Regarding PI implementation, another focus is active co-design of new DOI services, monitoring development of existing DOI products. Currently, DOI and its products are well known. Application of DOIs in publishing resources recorded in library and documentation areas, has fully established itself in large publishing houses like e.g. Springer and Elsevier. In the past, DOI services mainly covered commercial applications (see citation 6 for detailed information). At present, the DOI-F (DOI-Foundation) contacts national libraries to specify requirements of the "Library Community" and jointly develop corresponding new services. This item was discussed at the CoBRA+ meeting in July 2002, resulting in the decision that European national libraries (for a start, national libraries in the framework of CoBRA+) shall join the DOI-F. Die Deutsche Bibliothek is discussing details with further national libraries.

Results or products evolved from co-operation in DOI-F shall be analysed in terms of their functional applicability and cost-benefit ratio before integrating them into PI services. Co-operation shall also integrate Die Deutsche Bibliothek in the DOI network.

I.2 Scientific and technical project objectives

I.2.1 General outline

The underlying conditions outlined in the general project goal illustrate the common need for action in the URN area. Its practical realisation, however, must consider the complementary "DOI" development. This results in two overlapping working fields:

I.2.1.1 Uniform Resource Name (URN) scope

Structure of the URN string (assignment and administration)

Basic idea of URNs as Persistent Identifiers is strict separation of object identification through unique number and location reference (currently in the form of URLs). This section solely discusses the future form of the URN string structure.

The application of unequivocally structured, standardised URN numbers offers many advantages, e.g. referencing capability as standard number or persistent identification and resource access of distributed digital objects pursuant to different criteria.

In the long run, uniform structure of the URN string and co-ordinated URN assignment from the same namespace offer the greatest potential for technical realisation of a global resolving mechanism using the existing technical infrastructure of the Internet (see section below "Resolving mechanism"). This resides in the hierarchical structure of URNs[11]. By extracting namespaces from URN strings, the structure enables the automated identification of resolving services and, in case of a URN request, the user is delegated to service in charge of the respective URN string. This requires application of global, hierarchically structured URN namespaces with defined responsibilities of the participating institutions regarding URN assignment and resolving. The internationally administered URN namespace of national libraries, "NBN" ("National Bibliography Number"), fulfils these requirements. Distribution of work in this name space is based on the collection mandate of each national library, expressed by ISO country codes. Die Deutsche Bibliothek administers the sub namespace "urn:nbn:de". This hierarchical structure is continued at national level in Germany, as realised in the CARMEN-AP4 project. This also initiated application of an unequivocal structure of the URN string in Germany. Maintenance of URNs as standard numbers requires enhanced appropriate organisational and political framework. Thus, a co-ordinated, concerted, decentralised URN assignment becomes possible, and implementation of applications based on URNs is simplified. Vital condition for this is a national registration agency. Die Deutsche Bibliothek will act as such.

Resolving mechanism

The technical realisation of automatic redirection from URNs to URLs ("Resolving mechanism") is currently simulated by technical interim solutions ("Persistent-URL", Proxy-Server, PlugIn). However, approaches for universally applicable global resolving are specified. "DNS-NAPTR" (Domain Name System - Naming Authority PointR) is the most appropriate approach. It enables the embedding of the resolving mechanism in the DNS system. The DNS concept is based on the mapping of logic address names (domain name) to the unequivocal machine readable numbers (IP numbers). Then, domain names like e.g. http://deposit.ddb.de are resolved in assigned IP addresses like e.g. Different services have been implemented in the DNS system. NAPTR, one of these services, offers the possibility for resolving URNs.

At present, the organisational and technical levels of this area are still in development. In June 2002, several components necessary for URN resolution using the NAPTR technology were standardised. However, practical applications of NAPTR have been implemented within the URN context. Therefore, active co-design in developing standards and procedures is to be continued.

Technical requirements

To ensure high technical availability of URN services, technical solutions regarding the establishment of URN resolution services and high performance in answering URN requests, must be investigated and implemented. They must consider international developments for a long-term and platform independent use of these services.

A vital aspect is the processing of URN related information necessary for URN resolution of distributed, heterogeneous information system environments. For this purpose, the analysis of system independent interfaces for the exchange of data or meta data like the OAI protocol (Open Archives Initiative)[12] is needed.

URN marketing

URN marketing plays a key role in advertising the advantages of URNs as standard numbers. Target groups shall be sensitised and informed about it by means of e.g. presentations at meetings, publications, targeted contacting and work shops.

Internationally co-ordinated information bundling of further URN services and applications, guidelines for implementation of URN services, and progress in URN related standards have not yet been established on a regular basis. Die Deutsche Bibliothek will commit itself actively to this task and establish a so-called "International URN-Information Center" in the form of a web presentation.

For producers of network publications, products integrating URNs in documents during the creation process are most attractive. Therefore, companies and authors shall be addressed and sensitised for their use.

I.2.1.2 Digital Object Identifier scope

Within DOI-F membership, concepts, specifications, and goals are elaborated and determined by the "DOIs for Archiving" working group considering the following aspects:

Elaboration of strategy concept

Structure of DOIs (assignment and administration)

DOI meta data application profile "DOIs for Archiving"

Registration of DOIs requires their numbers and supply of a meta data set to DOI-F or RAs. Predominantly conceived designed for eCommerce users, the currently applied meta data sets do not conform to the requirements of Library Community. Thus, the meta data application profile "DOIs for Archiving" must be elaborated. To this end, internationally used meta data sets have to be reviewed in order to verify their applicability. If necessary, they are integrated to ensure compatibility of existing schemes.

DOI resolving mechanism

Technical requirements of new DOI services

On the basis of defined functional requirements of new DOI services in library and documentation areas, technical functions must be specified and solutions must be elaborated.

DOI marketing

The DOI marketing is covered by DOI-F.

I.2.1.3 Complementary use of Digital Object Identifiers and Uniform Resource Names

When considering user interests of producers, suppliers or end users of digital information and document classes, various application scenarios can be identified in whose contexts requirements can be fulfilled better by assignment of administration of Persistent Identifiers from the URN system [13] or by DOIs. Therefore, mechanisms ensuring parallel administration and resolving of URNs and DOIs must be developed.

I.2.1.4 Persistent Identifier (PI) products

Application of PIs enables development of consistent link structures on various object levels, like e.g. links in the object itself or links in gateways and online catalogues.

Services representing value added services for users may be consolidated on PI basis, like e.g. context sensitive links of heterogeneous, distributed digital information systems.

Other application scenarios are the integration of a PI search function in search engines or the use of URNs as bookmarks.

Internal business processes of companies for administration of distributed documents can be designed efficiently through application of PIs.

The integration of future oriented document structuring standards like XML offers enormous development potential in generating value added services, like e.g. establishing a semantic network.

I.2.2 Implementation at Die Deutsche Bibliothek

Creating conditions for complementary use of URNs and DOIs as well as integration of both systems in a PI portal provides the highest degree of benefit and acceptance from the perspective of service users of information services and data suppliers to Die Deutsche Bibliothek. Necessary fields of tasks are described in the following paragraphs.

I.2.2.1 Uniform Resource Name (URN) scope

Creating appropriate organisational framework conditions in the URN scope is as essential as the technical realisation of a PI service. For this purpose, Die Deutsche Bibliothek will establish a national "URN co-ordination agency".

Tasks and goals of Die Deutsche Bibliothek as national "URN co-ordination agency"

Starting from the results of the CARMEN-AP4 project, tasks in the following areas were identified:

Standardisation work
Structure of URN string

At present, the URN numeric system introduced in the project solely considers institutions affiliated to a library association. To enable URN assignment within the "NBN" namespace to non-affiliated institutions and to support the use of standardised URN numeric structures, it is necessary to extend guidelines for

These guidelines shall be determined in co-operation with representatives of library associations, with expert committees on standardisation and institutions interested in the "NBN" namespace.

URN assignment
URN administration

It is necessary to provide a co-ordinated structure of "URN registries" for the administration and registration of namespaces to implement co-ordinated URN assignment. One option is a centrally managed URN registry at Die Deutsche Bibliothek, and local registries maintained by the pertinent institutions. When establishing "URN-Registries", it is necessary to elaborate conceptual and technical recommendations in co-operation with library association representatives considering requirements of potential URN users like e.g. publishing houses.

URN resolving

Tasks in this area:

Further tasks are
I.2.2.2 Digital Object Identifier (DOI) scope

Due to the function of Die Deutsche Bibliothek regarding DOI, the following three fields of tasks have developed:

Die Deutsche Bibliothek as DOI user

This applies, when library and documentation institutions notify electronic documents by DOIs to be archived at Die Deutsche Bibliothek. Since no practical experience is available regarding bibliographic registration, administration, presentation or resolving of DOIs, workflows and technical solutions must be elaborated. Explanations on concrete planning for implementation at Die Deutsche Bibliothek are given under point "III.1.4 DOI scope".

Die Deutsche Bibliothek as contact for DOI related issues

This task will be fulfilled within the scope of the "URN co-ordination agency" where competences are bundled and central institutions will assure information channelling. It is advantageous for a user to address such a central institution.

Die Deutsche Bibliothek as active DOI-F member

Concrete working tasks depend on co-operative work planning of national libraries affiliated in DOI-F. During the term of the project, concrete proposals for solutions are elaborated on the following issues:

I.2.2.3 Complementary use of DOIs and URNs

On the basis of results regarding URN assignment and administration, co-operation in the DOI-F and requirements to integrate DOI services, conceptual and technical solutions are to be developed in the project.

I.2.2.4 Persistent Identifier (PI) products

Heterogeneous numeric structures and resolving mechanisms will probably be used.

For this reason, establishing a PI portal offers major advantages for users. Via a central entry site, users can resolve URNs of different namespaces, like e.g. URNs from "NBN" or "ISSN" namespace. Integration of enhanced functionalities would also make sense here, since the establishing effort pays for potential use. It is conceivable to offer search functions enabling users to find out whether a specific URL has received a URN, which institutions are taking part in URN assignment, how many URNs are registered, etc.

Internationally co-ordinated information bundling offers enormous development opportunities for other URN services, like e.g. central resolving service for the international namespace "NBN".

In parallel, services would be offered at a fee, like context dependent search in external databases based on meta data belonging to a URN or DOI and, as a result, supply of complete resources.

II. State of the art in science and technology; related scientific research

The present status is reflected in the results of the CARMEN-AP4 project. Also see project final report [14].

No new information was gained in interviews with suppliers of information system vendors (GBI, patent offices etc.)

III. Comprehensive description of working plan

III.1 Resource planning and management at Die Deutsche Bibliothek

III.1.1 International co-operation

Cooperation takes the form of active participation in the following organisations:

In addition, further co-operation with other institutions introducing URNs respectively DOIs or expanding existing services, will develop during the project.

III.1.2 National co-operation

At present (June 2002), there is co-operation with the following bodies, institutions, and organisations:

The following institutions are interested in introducing PIs:

III.1.3 Uniform Resource Name (URN) scope

Using existing business contacts of "Central bibliographic services" at Die Deutsche Bibliothek is a good means to address interested target groups. This includes presentations at conferences and trade shows (international book fair etc), distribution of flyers, etc.

Public relations activities also include lectures at conferences, e.g. at Conference of National Librarians, information events, workshops and further training courses, as well as consultancy when introducing URN services.

Infrastructure for the working areas URN assignment, administration and resolving mechanisms is not established yet (status, July 2002), but will be realised during the project. Details of the realisation are given under point III.2 "Content related scientific working plan".

III.1.4 Digital Object Identifier (DOI) scope

Die Deutsche Bibliothek does not yet have practical experience (status, July 2002) regarding DOI administration and application. Therefore, it will only be possible during the term of the project to realise integration in Die Deutsche Bibliothek in an appropriate organisational, personal and technical manner, depending on the results of co-design of new DOI services within DOI-F.

Regarding registration and archiving of electronic publications with DOIs at Die Deutsche Bibliothek, conditions for recording, administration and resolving of DOIs are created during the project period. This includes the following:

III.2 Content related scientific working plan

Two objective-derived working tasks are identified:

There are mutual dependencies, however.

III.2.1 Conception and project management

III.2.2 Technical implementation plan

Technical requirements of PI service

The objective is to implement a PI service oriented towards various application scenarios of selected test partners. The aim is to create a management system with interfaces to further applications independent of their functional criteria and technical conditions.

III.3 Project related resource planning, milestone planning (time line)

With regard to the time line, the following activities result from point III.2:

Complete Period Activities
6 months - 1. quarter
  • Technical and organisational consolidation of existing URN service at Die Deutsche Bibliothek
  • Formation of a URN working group
  • Concept for establishing a national URN Clearing Agency
  • Determination of digital object types for enhanced URN assignment to Die Deutsche Bibliothek
  • Elaboration of a concept for future structure of URN string structure
  • Concept for interregional, namespace-independent URN assignment
  • Concept for standardisation work
  • Concept for co-ordinated decentralised URN administration
  • Evaluation of software tools and hardware components for national PI service
  • Concept for co-operative international URN information centre of Die Deutsche Bibliothek and National Library of Helsinki
  • Elaboration of concept for formal and content-based co-operation with DOI-F, work sharing with other national libraries
6 months - 2. quarter
  • Determination of (content-related) tasks of URN working group
  • Determination of requirements and organisational integration of URN clearing agency
  • Determination of type of co-operation with organisations for standardisation work
  • Concretisation of "Policies" for URN assignment
  • Initiation of technical development of national PI service
  • Specification of tasks for co-operation with DOI-F
  • Concretisation resp. evaluation of software components for potential integration of DOI services
6 months - 3. quarter
  • Implementation, specification and enhancement of elaborated concepts
  • Tests and further development of PI service
6 months - 4. quarter
  • Continuation of co-operation with pertinent organisations and institutions
  • Adaptation and application of PI service

The activities listed in the following table are executed in parallel to the above-mentioned tasks.

Activities Period
Active participation in establishing standards on technical realisation of a global resolving mechanism for W3C, IETF and IESG 1. - 4. quarter
URN marketing by conference presentations, further training events, workshops etc. 1. - 4. quarter
Active participation in DOI-F 1. - 4. quarter
Central contact on PI issue 1. - 4. quarter
Research into new PI development, institutional framework conditions, URN/DOI products, evaluation of technical tools 1. - 4. quarter
Technical maintenance and further development of resolving service 1. - 4. quarter

The realisation of individual tasks depends on the co-operation with organisations and institutions on the one hand and the technical realisation of PI services on the other hand. For this reason, precise planning (status July 2002) is not possible at present.

Contributions of Die Deutsche Bibliothek

Components established during the project period of CARMEN-AP4 are already used in routine operation at Die Deutsche Bibliothek. Transition from project to regular operation is contributed by Die Deutsche Bibliothek.

IV. Working packages/national and international co-operation

At present, precise listing of national and international co-operation partners or institutions which plan to introduce PI service is not available.

V. Operating plan

Planned project results

Planned result utilisation

VI. Funding requirements

(Follow-up funding)

The tasks outlined require follow-up funding:

The period of this project shall be two years.

Index of abbreviations:

AfSArbeitsstelle für Standardisierung ((Office for Standardisation)
AG-VerbundsystemeArbeitsgemeinschaft der Verbundsysteme (Working Community of Association Systems)
BISBibliotheks- und Informationssystem der Carl von Ossietzky Universität, Oldenburg ((Library and Information System of Carl von Ossietzky University, Oldenburg)
BVBBibliotheksverbund Bayern (Library Association, Bavaria)
CARMENContent Analysis, Retrieval and MetaData: Effective Networking
CARMEN-AP4Content Analysis, Retrieval and MetaData: Effective Networking - working package 4
CDNLConference of Directors of National Libraries
CENLConference of European National Libraries
CNRICorporation for National Research Initiatives
CoBRA+Computerized Bibliographic Record Actions
DNS-NAPTRDomain Name System - Naming Authority PointR
DOIDigital Object Identifier
GBIGesellschaft für betriebliche Information ((Society for Business Information)
GBVGemeinsamer Bibliotheksverbund (Joint Library Association) of Federal States Bremen, Hamburg, Mecklenburg-Eastern Pommerania, Lower Saxony, Saxony-Anhalt, Schleswig-Holstein and Thuringia
HBZHochschulbibliothekszentrum des Nordrhein-Westfälischen Bibliotheksverbundes (University Library Centre of Northrhine-Westphalian Library Association)
HEBISHessisches BibliotheksInformationsSystem (Hessian Library Information System)
HTTPHypertext Transfer Protocol
KOBVKooperativer Bibliotheksverbund Berlin-Brandenburg (Co-operative Library Association)
IESGInternet Engineering Steering Group
IETFInternet Engineering Task Force
ISBNInternational Standard Book Number
ISSNInternational Standard Serial Number
OAIOpen Archives Initiative
OPACOnline Public Access Catalogue
PIPersistent Identifier
RARegistration Agency
SOAPplatform- and system independent protocol for data Exchange, using XML as syntax
SWBSüdwestdeutscher Bibliotheksverbund (Southwest German Library Association)
URCUniform Resource Characteristic
URIUniform Resource Identifier
URLUniform Resource Locator
URNUniform Resource Name
XMLExtensible Markup Language
W3CWorld Wide Web Consortium


[1] DOI-Homepage: http://www.doi.org

[2] Information on URNs available at URL: http://www.ietf.org/html.charters/urn-charter.html

[3] Uniform Resource Identifier is an abstract generic term for URLs, URNs and URCs (Uniform Resource Characteristics).

[4] Internet standards are published in the form of RFCs (Request for Comments). URN related RFCs are available at URL: http://www.ietf.org/html.charters/urn-charter.html

[5] http://www.handle.net

[6] Information on URN applications is available at: http://www.uri.net/urn-nid-status.html
Descriptions and further information on DOI services are available at: http://www.doi.org/registration_agencies.html

[7] Project homepage: http://www.bis.uni-oldenburg.de/carmen_ap4
Funding sign: 08SFC061, formal and financial integration of Die Deutsche Bibliothek in CARMEN-AP12 with funding sign: 08SFC061

[8] See final report on CARMEN-AP4 project as annex 1: to Nr. 3.1. BnBest-BMBF 98

[9] During the test phase, already 30% of the university libraries decided to participate, 40 % indicated interest.

[10] At present, the URN service of Die Deutsche Bibliothek for URN resolving in URL is hit 2.5 times on the average for each URN. (Until July 2002, 1016 URNs were resolved 2763 times.)

[11] URNs consist of several hierarchically structured components, including namespace (NID) composed of several subname spaces (SNID), and the namespace specific string (NISS). The following example illustrates the general URN structure: . Within URNs, existing numeric systems like e.g. ISBN and institution-based numeric systems on regional or international level can be realised as namespaces like "National Bibliography Number" (NBN).

[12] Open Archives Initiative (http://www.openarchives.org/)

[13] This may be URNs within "NBN" namespace or from external namespaces.

[14] See final report of CARMEN-AP4 project as annex 1: to no. 3.1. BnBest-BMBF 98