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International Federation of Associations and Institutions UNIVERSAL DATAFLOW AND TELECOMMUNICATIONS CORE PROGRAMME OCCASIONAL PAPER 8

DIGITAL : DEFINITIONS, ISSUES AND CHALLENGES

Gary Cleveland IFLA UDT Core Programme

March, 1998 International Federation of Library Associations and Institutions UNIVERSAL DATAFLOW AND TELECOMMUNICATIONS CORE PROGRAMME

The IFLA Core Programme on Universal Dataflow and Telecommunications (UDT) seeks to facilitate the international and national exchange of electronic data by providing the library community with pragmatic approaches to resource sharing. The programme monitors and promotes the use of relevant standards, promotes the use of relevant technologies and monitors relevant policy issues in an effort to overcome barriers to the electronic transfer of data in library fields.

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IFLA International Office for UDT c/o of Canada 395 Wellington Street Ottawa, CANADA K1A 0N4

UDT Staff Contacts:

Leigh Swain, Director Email: [email protected] Phone: (819) 994-6833

or

Louise Lantaigne, Administration Officer Email: [email protected] Phone: (819) 994-6963

Fax: (819) 994-6835

Email: [email protected]

URL: http://www.ifla.org/udt/

Occasional papers are available electronically at: http://www.ifla.org/udt/op/ UDT Occasional Papers # 8

Universal Dataflow and Telecommunications Core Programme International Federation of Library Associations and Institutions

DIGITAL LIBRARIES: Definitions, Issues and Challenges

Gary Cleveland UDT Core Programme [email protected] March, 1998

The idea of easy, finger-tip access to information— each of these different phrases meant. “Digital what we conceptualize as digital libraries today— library” is simply the most current and most widely began with Vannenar Bush’s Memex machine accepted term and is now used almost exclusively at (Bush, 1945) and has continued to evolve with each conferences, online, and in the literature. advance in . With the arrival of computers, the concept centered on large Another factor adding to the confusion is that digital bibliographic , the now familiar online libraries are at the focal point of many different areas retrieval and public access systems that are part of of research, and what constitutes a any contemporary library. When computers were differs depending upon the research community that connected into large networks forming the Internet, is describing it (Nurnberg, et al, 1995). For the concept evolved again, and research turned to example: creating libraries of digital information that could be accessed by anyone from anywhere in the world. · from an point of view, it is Phrases like “virtual library,” “electronic library,” a large “library without walls” and, most recently, “digital · for people who work on technology, it library,” all have been used interchangeably to is one particular application of hypertext describe this broad concept. methods · for those working in wide-area information But what does this phrase mean? What is digital delivery, it is an application of the Web library? And what are the issues and challenges in · and for library science, it is another step in the creating them? Moreover, what are the issues continuing automation of libraries that began involved in creating a coordinated scheme of digital over 25 years ago libraries? It has been suggested that digital libraries will only be viable within such a scheme (Chapman In fact, a digital library is all of these things. These and Kenny, 1996). This paper provides a very high- different research approaches will all add to the level overview of digital libraries and briefly outlines development of digital libraries. each of these questions in turn. Third, confusion arises from the fact that there are 1. WHAT IS A DIGITAL LIBRARY? many things on the Internet that people are calling “digital libraries,” which¾from a ’s point What is a digital library? There is much confusion of view¾are not. For example: surrounding this phrase, stemming from three factors. First, the library community has used · for computer scientists and software developers, several different phrases over the years to denote this collections of computer algorithms or software concept—electronic library, virtual library, library programs are digital libraries. without walls—and it never was quite clear what · for database vendors or commercial document suppliers, their databases and electronic that libraries do to develop and organize collections document delivery services and digital libraries. and to help users find information. · for large corporations, a digital library is the document systems that control The institutions involved in the American Digital their business documents in electronic form. Library Federation came up with a similar notion of · for a publisher, it may be an online version of a “digital library.” It also emphasizes the traditional catalogue. underpinnings of libraries—selection, access, and · and for at least one very large software preservation—as well as the fact that digital libraries company, a digital library is the collection of will necessarily be constructed to serve particular whatever it can buy the rights to, and then communities (Waters, 1998): charge people for using. Digital libraries are organizations that provide A fairly spectacular example of what many people the resources, including the specialized staff, to consider to be a digital library today is the World select, structure, offer intellectual access to, Wide Web. The Web is a gathering of thousands interpret, distribute, preserve the integrity of, and ensure the persistence over time of and thousands of documents. Many would call this collections of digital works so that they are huge collection a digital library because they can readily and economically available for use by a find information, just as they can do banking in a defined community or set of communities. “digital bank” or buy compact discs in a “digital record store.” Yet, is the Web a digital library? With the assumption that digital libraries are According to Clifford Lynch, once of the leading libraries first and foremost, we can list some scholars in the area of digital library research, it is characteristics. These characteristics have been not. Lynch (1997:52) states: gleaned from various discussions about digital libraries, both online and in print (See Arms, 1995; One sometimes hears the Internet characterized Graham, 1995a; Chepesuik, 1997; Lynch and as the world's library for the digital age. This Garcia-Molina, 1995): description does not stand up under even casual examination. The Internet¾and particularly its collection of multimedia resources known as the · digital libraries are the digital face of traditional ¾was not designed to support libraries that include both digital collections and the organized publication and retrieval of traditional, fixed media collections. So they information as libraries are. It has evolved into encompass both electronic and paper materials. what might be thought of as a chaotic repository for the collective output of the world's digital · digital libraries will also include digital "printing presses."...... In short, the Net is not a materials that exist outside the physical and digital library. administrative bounds of any one digital library

Thus, in examining the various examples of what are · digital libraries will include all the processes called digital libraries, it appears that have and services that are the backbone and nervous been confused about what a digital library is, that the system of libraries. However, such traditional word “library” has been appropriated by many processes, though forming the basis digital different groups to describe either their areas of library work, will have to be revised and research or signify a simple collection of digital enhanced to accommodate the differences objects. between new digital media and traditional fixed media. So what is a working definition of “digital library” that makes sense to librarians? As a starting point, · digital libraries ideally provide a coherent view we should assume that digital libraries are libraries of all of the information contained within a with the same purposes, functions, and goals as library, no matter its form or format traditional libraries¾ and management, subject analysis, index creation, · digital libraries will serve particular provision of access, , and communities or constituencies, as traditional preservation. A narrow focus on digital formats libraries do now, though those communities may alone hides the extensive behind-the-scenes work be widely dispersed throughout the network.

Digital Libraries: Definitions, Issues and Challenges - 2 - · digital libraries will require both the skills of · high-speed local networks and fast connections librarians and well as those of computer to the Internet scientists to be viable. · relational databases that support a variety of digital formats One thing digital libraries will not be is a single, · full text search engines to index and provide completely digital system that provides instant access access to resources to all information, for all sectors of society, from · a variety of servers, such as Web servers and anywhere in the world. This is simply unrealistic. FTP servers This concept comes from the early days when people · electronic document management functions that were unaware of the complexities of building digital will aid in the overall management of digital libraries. Instead, they will most likely be a resources collection of disparate resources and disparate systems, catering to specific communities and user One important thing to point out about technical groups, created for specific purposes. They also will architectures for digital libraries is that they won’t be include, perhaps indefinitely, paper-based monolithic systems like the turn-key, single box collections. Further, interoperability across digital OPAC’s with which librarians are most familiar. libraries—of technical architectures, , and Instead, they will be a collection of disparate systems document formats—will also only likely be possible and resources connected through a network, and within relatively bounded systems developed for integrated within one interface, most likely a Web those specific purposes and communities. interface or one of its descendants. For example, the resources supported by the architecture could For librarians, this definition of a digital library, and include: these characteristics, are the most logical because it expands and extends the traditional library, · bibliographic databases that point to both paper preserves the valuable work that they do, while and digital materials integrating new technologies, new processes, and · indexes and finding tools new media. · collections of pointers to Internet resources · directories 2. WHAT ARE THE ISSUES AND · primary materials in various digital formats CHALLENGES IN CREATING DIGITAL · photographs LIBRARIES? · numerical data sets · and electronic journals The optimism and hype from the early 1990’s has been replaced by a realization that building digital Though these resource may reside on different libraries will be a difficult, expensive, and long-term systems and in different databases, they would effort (Lynch and Garcia-Molina, 1995). Creating appear as though there were one single system to the effective digital libraries poses serious challenges. users of a particular community. The integration of digital media into traditional collections will not be straightforward, like previous Within a coordinated digital library scheme, some new media (e.g., video and audio tapes), because of common standards will be needed to allow digital the unique nature of digital information¾it is less libraries to interoperate and share resources. The fixed, easily copied, and remotely accessible by problem, however, is that across multiple digital multiple users simultaneously. Some the more libraries, there is a wide diversity of different data serious issues facing the development of digital structures, search engines, interfaces, controlled libraries are outlined below. vocabularies, document formats, and so on. Because of this diversity, federating all digital libraries 2.1 Technical architecture nationally or internationally would an impossible effort. Thus, the first task would be to find sound The first issue is that of the technical architecture reasons for federating particular digital libraries into that underlies any digital library system. Libraries one system. Narrowing the field in such a manner will need to enhance and upgrade current technical would reduce the technical and political hurdles architectures to accommodate digital materials. The required to establish common practices. Further, architecture will include components such as: because of the often uncertain futures of both de jure

IFLA UDT Core Programme Occasional Paper - 3 - and defacto standards over time, what those digitizes what materials could be based on factors standards are is unclear. such as:

2.2 Building digital collections · collection strengths. A particular library with a strong collection focus could be responsible for One of the largest issues in creating digital libraries digitizing selected portions of it and adding new will be the building of digital collections. Obviously, digital works to it. for any digital library to be viable, it must eventually have a digital collection with the critical mass to · unique collections. If a library has the only make it truly useful. There are essentially three copies of something, they are obviously the ones methods of building digital collections: to digitize it

1. digitization, converting paper and other media · the priorities of user communities. Such in existing collections to digital form (discussed priorities will justify holding the materials in more detail below). locally, for example, because of the demands of 2. acquisition of original digital works created by a curriculum publishers and scholars. Example items would be electronic books, journals, and datasets. · manageable portions of collections. When 3. access to external materials not held in-house there is no other overriding criteria, then by providing pointers to Web sites, other library material can be divided up among institutions collections, or publishers’ servers. simply according to what is reasonable for any one institution to collect or digitize While the third method may not exactly constitute part of a local collection, it is still a method of · technical architecture. The state of a library’s increasing the materials available to local users. technical architecture will also be factor in One of main issues here is the degree to which selecting who digitizes what. A library must libraries will digitize existing materials and acquire have a technical architecture up to the task of original digital works, as opposed to simply pointing support a particular digital collection. to them externally. This a reprise of the old access versus ownership issue¾but in the digital · skills of staff. Institutions whose staff don’t realm¾with many of the same concerns such as: have the necessary skills can’t become a major node in a national scheme. · local control of collections · long-term access and preservation Yet, no matter how a collection is built—of materials digitized in-house, of original digital works, or of What about digital collection building in a providing access to materials by pointing to other coordinated scheme? There are many reasons why external resources¾libraries in a collective must building digital collections is a good candidate for ensure it is preserved and made available in coordinated activity. First, acquiring digital works perpetuity. For example, if the only copies of digital and doing in-house digitization are expensive, works reside on a particular publisher’s server, then especially to undertake alone. By working together, what happens if the publisher goes bankrupt? Or if institutions with common goals can gain greater the market value of a particular work approaches efficiencies and reduce the overall costs involved in zero? What if all of part of a digital collection of a these activities, as was the case with retrospective library were lost, such as through some catastrophic conversion of bibliographic records. Second, it also event? Ensuring long-term preservation and access reduces the redundancy and waste of acquiring or will require policies and a scheme by which converting materials more than once. Third, redundant permanent copies are stored at designated coordinated digital collection building enhances institutions. Preservation issues will be discussed resource sharing and increases the richness of further later in the paper. collections to which users have access.

How can specific materials to be processed by a given institution be identified? Who collects and/or

Digital Libraries: Definitions, Issues and Challenges - 4 - 2.3 Digitization possible with original materials (e.g., fragile, rare materials) Recall that one of the primary methods of digital · and whether restrictions or licensing collection building is digitization. What does this will permit conversion. term mean exactly? Simply put, it is the conversion of any fixed or analogue media¾such as books, 2.4 Metadata journal articles, photos, paintings, microforms¾into electronic form through scanning, sampling, or in Metadata is another issue central to the development fact even re-keying. An obvious obstacle to of digital libraries. Metadata is the data the digitization is that it is very expensive. One estimate describes the content and attributes of any particular from the University of Michigan at Ann Arbor, the item in a digital library. It is a concept familiar to organization responsible for the JSTOR project, puts librarians because it is one of the primary things that the cost of digitizing a single page at $2 to $6 dollars librarians do¾they create cataloguing records that US (Chepesuik, 1997:48). describe documents. Metadata is important in digital libraries because it is the key to resource How do you go about deciding what parts of a discovery and use of any document. Anyone who collection to digitize? There are several approaches has used Alta Vista, Excite, or any of the other available, at least theoretically: search engines on the Internet knows that simple full-text searches don’t scale in a large network. · retrospective conversion of collections— One can get thousands of hits, but most of them will essentially, starting at A and ending up a Z. be irrelevant. While there are formal library However ideal such complete conversion would standards for metadata, namely AACR, such records be, it is impractical or impossible technically, are very time-consuming to create and require legally, and economically. This approach can specially trained personnel. Human cataloguing, arguably be dispensed with as a pipe dream. though superior, is just too labour extensive for the already large and rapidly expanding information · digitization of a particular special collection environment. Thus, simpler schemes for metadata or a portion of one. A small collection of are being proposed as solutions. manageable size, and which is highly valued, is a prime candidate. While they are still in their infancy, a number of schemes have emerged, the most prominent of which · highlight a diverse collection by digitizing is the , an effort to try and determine the particularly good examples of some collection “core” elements needed to describe materials. The strength first workshop took place at OCLC headquarters in Dublin, Ohio, hence the name “Dublin Core.” The · high-use materials, making those materials that Dublin Core workshops defined a set of fifteen are in most demand more accessible. metadata elements¾much simpler than those used in traditional library cataloguing. They were · an ad hoc approach, where one digitizes and designed to be simple enough to be used authors, but stores materials as they are requested. This is, at the same time, descriptive enough to be useful in however, a haphazard method of digital resource discovery. collection building. The lack of common metadata standards—ideally, These approaches can be used alone or in defined for use in some specified context—is yet combination depending upon a particular another a barrier to information access and use in a institution’s goals for digitization. digital library, or in a coordinated digital library scheme. Nested within these approaches are several criteria for selecting individual items. These include: 2.5 Naming, identifiers, and persistence

· their potential for long-term use The fifth issue is related to metadata. It is the · their intellectual or cultural value problem of naming in a digital library. Names are · whether they provide greater access than strings that uniquely identify digital objects and are part of any document’s metadata. Names are as

IFLA UDT Core Programme Occasional Paper - 5 - important in a digital library as an ISBN number is names (Lynch, 1998). in a traditional library. They are needed to uniquely identify digital objects for purposes such as: · (URN). URNs are a development of the Internet Engineering Task · citations Force (IETF). A URN is not a naming scheme · information retrieval in itself, but a framework for defining identifiers · to make links among objects (Lynch, 1998). They contain a naming · and for the purposes of managing copyright authority identifier (a central authority given the task of assigning identifiers) and an object Any system of naming that is developed must be identifier (assigned by the central authority). permanent, lasting indefinitely. This means, among Like PURLs, URNs must be resolved, through a other things, that the name can’t be bound up with a database or other such system, into actual . specific location. The unique name and its location Unlike PURLs, however, a URN can be resolved must be separate. This is very much unlike URLs, into more than one URL, such as one for each of the current method for identifying objects on the several different formats. There is currently no Internet. URL’s confound in one string several working URN system. items that should be separate. They include the method by which a document is accessed (e.g., · Digital Object Identifier (DOI) System. DOI HTTP), a machine name and document path (its is an initiative by the Association of American location), and a document file name which may or Publishers and the (American) Corporation for may not be unique (e.g., how many index.html files National Research Initiatives designed to do you have on your Web site?). URLs are very bad provide a method by which digital objects can be names because whenever a file is moved, the reliably identified and accessed. The CNRI document is often lost entirely. Handle system, which underlies DOI, is a system that resolves digital identifiers into the A global scheme of unique identifiers is required, information required to locate and access a one that has persistence beyond the life of the digital object. The main impetus of the DOI originating organization and that is not tied to system is to provide publishers with a method by specific locations or processes. These names must which the intellectual property right issues remain valid whenever documents are moved from associated with their materials can be managed.2 one location to another, or are migrated from one storage medium to another. The issue of persistent naming raises it head in a coordinated scheme, as well. Persistent names is an Three examples of schemes proposed to get around organizational problem, rather than an engineering the problem of persistent naming are PURLs, URNs, problem. Technically, a system to handle names is and Digital Object Identifiers. possible, however, unique identifiers will only persist if some institution takes responsibility for their · PURLS. PURLs are persistent URLs. They are management and migration from a current a scheme developed by OCLC in an attempt to technology to succeeding generations of separate a document name from its location and technologies. Thus, one goal of a coordinated digital therefore increase the probability that it will library scheme would be to identify an institution or always be found. PURLs work through a institutions that would take charge of issuing, mapping of a unique, never-changing PURL to resolving, and migrating a system of unique names. an actual URL. If a document moves, the URL is updated, but the PURL stays the same. In 2.6 Copyright / rights management operation, a user requests a document through a PURL, a PURL server looks up the Copyright has been called the “single most vexing corresponding URL in a database, and then the barrier to digital library development” (Chepesuik, URL is used to pass the document to the user.1 1997:49). The current paper-based concept of Because PURLs also confound a name with an copyright breaks down in the digital environment access method, like URLs, they are not true because the control of copies is lost. Digital objects

1 For more information, see www.purl.org. 2 See www.doi.org.

Digital Libraries: Definitions, Issues and Challenges - 6 - are less fixed, easily copied, and remotely accessible stored on older media could be lost because by multiple users simultaneously. The problem for there will no longer have the hardware or libraries is that, unlike private businesses or software to read them. Thus, libraries will have publishers that own their information, libraries are, to keep moving digital information from storage for the most part, simply caretakers of medium to storage medium. information¾they don’t own the copyright of the material they hold. It is unlikely that libraries will · the preservation of access to content. This ever be able to freely digitize and provide access to form of preservation involves preserving access the copyrighted materials in their collections. to the content of documents, regardless of their Instead, they will have to develop mechanisms for format. While files can be moved from one managing copyright, mechanisms that allow them to physical storage medium to another, what provide information without violating copyright, happens when the formats (e.g., Adobe Acrobat called rights management. PDF) containing the information become obsolete? This is a problem perhaps bigger than Some rights management functions could include, that of obsolete storage technologies. One for example: solution is to do data migration¾that is, translate data from one format to another · usage tracking preserving the ability of users to retrieve and · identifying and authenticating users display the information content. However, there · providing the copyright status of each digital are difficulties here too—data migration is object, and the restrictions on its use or the fees costly, there are as yet no standards for data associated with it migration, and distortion or information loss is · handling transactions with users by allowing inevitably introduced every time data is only so many copies to be accessed, or by migrated from format to format. charging them for a copy, or by passing the request on to a publisher The bottom line is that no one really knows how yet how to best migrate digital information. 2.7 Preservation Preserving digital information: The Report of the Task Force on Archiving of Digital Another important issue is preservation¾keeping Information (RLG, 1995) by the US digital information available in perpetuity. In the Commission on Preservation and Access and preservation of digital materials, the real issue is RLG states, “the preservation community is only technical obsolescence. Technical obsolescence in beginning to address migration of complex the digital age is like the deterioration of paper in digital objects” and such migration remains the paper age. Libraries in the pre-digital era had to “largely experimental.” Even if there were worry about climate control and the de-acidification adequate technology available today, of books, but the preservation of digital information information will have to be migrated from will mean constantly coming up with new technical format to format over many generations, passing solutions. a huge and costly responsibility to those who come after. When considering digital materials, there are three types of “preservation” one can refer to: · the preservation of fixed-media materials through digital technology. This slant on the · the preservation of the storage medium. issue involves the use of digital technology as a Tapes, hard drives, and floppy discs have a very replacement for current preservation media, short life span when considered in terms of such as microforms. Again, there are, as yet, no obsolescence. The data on them can be common standards for the use of digital media refreshed, keeping the bits valid, but refreshing as a preservation medium and it is unclear is only effective as long as the media are still whether digital media are as yet up to the task of current. The media used to store digital long-term preservation. materials become obsolete in anywhere from two standards will be required to consistently store to five years before they are replaced by better and share materials preserved digitally technology. Over the long term, materials (Chepesuik, 1997).

IFLA UDT Core Programme Occasional Paper - 7 - Graham, P.S. (1995b). Long-term intellectual preservation. URL: http://aultnis.rutgers.edu/texts/dps.html What can libraries jointly do in a coordinated scheme? They can: Lesk, M. (1996). Going digital. Scientific American. March, 1996, 58-60. Also available at: URL: http://www.sciam.com/0397issue/0397lesk.html · create policies for long-term preservation · ensure that redundant permanent copies are Lynch, CA (1995). The Tulip project: context, history, and stored at designated institutions perspective. Library Hi Tech, 52(13), 8-24. · help establish preservation standards to Lynch, C.A. (1997). Searching the Internet. Scientific American, consistently store and share materials preserved March, 1997, 52-56. Also available at: URL: digitally http://www.sciam.com/0397issue/0397lynch.html Lynch, CA. and Garcia-Molina, H. (1995). Interoperability, 3.0 CONCLUSION scaling, and the digital libraries research agenda: a report on the May 18-19, 1995 IITA Digital Libraries Workshop. URL: http://www-diglib.stanford.edu/diglib/pub/reports/iita- Libraries around the world have been working on dlw/main.html this daunting set of challenges for several years now. They have created many digital library initiatives Lynch, C.A. (1998). Identifiers and their role in networked and projects, and have formed various national information applications. Feliciter, January, 1998, pp. 31-35. schemes for jointly exploring key issues. With Masinter, L. (1995). Document management, digital libraries, and several years accumulated experience, the initial the Web. URL: enthusiasm surrounding the development of the http://www.cernet.edu.cn/HMP/PAPER/243/html/paper.htm digital library has been replaced by sober second Miller, J.S. (1996). W3C and digital libraries. D-Lib Magazine, thought. Librarians have discovered that, with a few November, 1996. URL: exceptions, making a business case for digitization http://www.dlib.org/dlib/november96/11miller.html and investments in digital technology is more Nurnberg, P.J., Furuta, R., Leggett, J.J., Marshall, C., and Shipman difficult than first envisioned, especially given the III, F.M. (1995). Digital libraries: issues and architectures. In technical and legal constraints that must first be Proceedings of the Second Annual Conference on the Theory and Practice of Digital Libraries. Austin, Texas, June 11-13, overcome. As with most other technical 1995, pp. 147-153. developments in libraries over the years, we will have to move forward in small, manageable, Schatz, B. and Chen, H. (1996) Building large-scale digital libraries. Computer, May, 1996. Also available at: URL: evolutionary steps, rather than in an rapid http://www.computer.org/pubs/computer/dli/ revolutionary manner. Shreeves, E. (1997). Is here a future for cooperative collection SELECTED SOURCES development in the digital age? Library Trends, 4(3), 373-390. Steele, Colin. (1995). The digital library: do's, don'ts and Arms, W.Y. (1995). Key concepts in the architecture of the developments. The Electronic Library, 13(5), 435-437. digital library. D-lib Magazine, July, 1995. URL: http://www.dlib.org/dlib/July95/07arms.html Stefik, M. (1997). Trusted systems. Scientific American, March, 1997, 78-81. Also available at: URL: Bush, V., “As We May Think”, Atlantic Monthly, July 1945, pp. http://www.sciam.com/0397issue/0397stefik.html 101-108. RLG. (1995) Preserving digital information: The Report of the Chapman, S. and Kenny, A.R. (1996). Digital conversion of Task Force on Archiving of Digital Information. materials: a case for full informational capture. Commissioned by the Commission on Preservation and Access D-lib Magazine, October, 1996. URL: and the Research Libraries Group. URL: http://www.dlib.org/dlib/october96/cornell/10chapman.html http://www.rlg.org/ArchTF/tfadi.index.htm

Chepesuik, R. (1997). The future is here: America's libraries go Waters, D.J. (1998). What are digital libraries? CLIR Issues, digital. American Libraries, 2(1), 47-49. July/August. URL: http://www.clir.org/pubs/issues/issues04.HTML Erway, R.L. (1996). Digital initiatives of the Research Libraries Group. D-Lib Magazine, December, 1996. URL: Weibel, S. (1995). Metadata: The Foundations of Resource http://www.dlib.org/dlib/december96/rlg/12erway.html Description. D-Lib Magazine, July 1995. URL: http://www.dlib.org/dlib/July95/07weibel.html Graham, P.S. (1995a). Requirements for the digital research library. URL: http://aultnis.rutgers.edu/texts/DRC.html

Digital Libraries: Definitions, Issues and Challenges - 8 -