Digital library

From Wikipedia, the free encyclopedia

A digital library is a library in which collections are stored in digital formats (as opposed to print, microform, or other media) and accessible by computers.[1] The digital content may be stored locally, or accessed remotely via computer networks. A digital library is a type of information retrieval system.

The first use of the term digital library in print may have been in a 1988 report to the Corporation for National Research Initiatives[2] The term digital libraries was first popularized by the NSF/DARPA/NASA Digital Libraries Initiative in 1994.[3] The older names electronic library or virtual library are also occasionally used, though electronic library nowadays more often refers to portals, often provided by government agencies, as in the case of the Florida Electronic Library.

Contents

[edit] Types of digital libraries

The term digital library is diffuse enough to be applied to a wide range of collections and organizations, but, to be considered a digital library, an online collection of information must be managed by and made accessible to a community of users. Thus, some web sites can be considered digital libraries, but far from all. Many of the best known digital libraries are older than the web including Project Perseus, Project Gutenberg, and ibiblio. Nevertheless, as a result of the development of the internet and its search potential, digital libraries such as the European Library and the Library of Congress are now developing in a Web-based environment. Public, school and college libraries are also able to develop digital download websites, featuring eBooks, audiobooks, music and video, through companies like OverDrive, Inc.

A distinction is often made between content that was created in a digital format, known as born-digital, and information that has been converted from a physical medium, e.g., paper, by digitizing. The term hybrid library is sometimes used for libraries that have both physical collections and digital collections. They consist of a combination of traditional preservation efforts such as microfilming and new technologies involving digital projects. For example, American Memory is a digital library within the Library of Congress. Some important digital libraries also serve as long term archives, for example, the ePrint arXiv, and the Internet Archive.

[edit] Academic repositories

Many academic libraries are actively involved in building institutional repositories of the institution's books, papers, theses, and other works which can be digitized or were 'born digital'. Many of these repositories are made available to the general public with few restrictions, in accordance with the goals of open access. Institutional, truly free, and corporate repositories are often referred to as digital libraries.

[edit] Digital archives

Archives differ from libraries in several ways. Traditionally, archives were defined as:

  1. Containing primary sources of information (typically letters and papers directly produced by an individual or organization) rather than the secondary sources found in a library (books, etc);
  2. Having their contents organized in groups rather than individual items. Whereas books in a library are cataloged individually, items in an archive are typically grouped by provenance (the individual or organization who created them) and original order (the order in which the materials were kept by the creator);
  3. Having unique contents. Whereas a book may be found at many different libraries, depending on its rarity, the records in an archive are usually one-of-a-kind, and cannot be found or consulted at any other location except at the archive that holds them.

The technology used to create digital libraries has been even more revolutionary for archives since it breaks down the second and third of these general rules. The use of search engines, Optical Character Recognition and metadata allow digital copies of individual items (i.e. letters) to be cataloged, and the ability to remotely access digital copies has removed the necessity of physically going to a particular archive to find a particular set of records. The Oxford Text Archive is generally considered to be the oldest digital archive of academic primary source materials.

Project Gutenberg, Google Book Search, Windows Live Search Books, Internet Archive, Cornell University, The Library of Congress World Digital Library, The Digital Library at the University of Michigan, and CMU's Universal library are considered leaders in the field of digital archive creation and management. There are hundreds of regionals such as the Wisconsin Historical Society. The Vatican maintains an extensive digital library inventory and associated technology. The entire works of Martin Luther are held at Emory University and are being digitized under an $8M Grant from Coca-Cola heirs, and the Packard Foundation maintains digitization facilities near the Acropolis in Athens, Greece, as examples.

[edit] The future

Large scale digitization projects are underway at Google, the Million Book Project, MSN, and Yahoo!. With continued improvements in book handling and presentation technologies such as optical character recognition and ebooks, and development of alternative depositories and business models, digital libraries are rapidly growing in popularity as demonstrated by Google, Yahoo!, and MSN's efforts. Just as libraries have ventured into audio and video collections, so have digital libraries such as the Internet Archive.

[edit] Searching

Most digital libraries provide a search interface which allows resources to be found. These resources are typically deep web (or invisible web) resources since they frequently cannot be located by search engine crawlers. Some digital libraries create special pages or sitemaps to allow search engines to find all their resources. Digital libraries frequently use the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) to expose their metadata to other digital libraries, and search engines like Google Scholar, Google, Yahoo! and Scirus can also use OAI-PMH to find these deep web resources.[4]

There are two general strategies for searching a federation of digital libraries:

  1. distributed searching, and
  2. searching previously harvested metadata.

Distributed searching typically involves a client sending multiple search requests in parallel to a number of servers in the federation. The results are gathered, duplicates are eliminated or clustered, and the remaining items are sorted and presented back to the client. Protocols like Z39.50 are frequently used in distributed searching. A benefit to this approach is that the resource-intensive tasks of indexing and storage are left to the respective servers in the federation. A drawback to this approach is that the search mechanism is limited by the different indexing and ranking capabilities of each database, making it difficult to assemble a combined result consisting of the most relevant found items.

Searching over previously harvested metadata involves searching a locally stored index of information that has previously been collected from the libraries in the federation. When a search is performed, the search mechanism does not need to make connections with the digital libraries it is searching - it already has a local representation of the information. This approach requires the creation of an indexing and harvesting mechanism which operates regularly, connecting to all the digital libraries and querying the whole collection in order to discover new and updated resources. OAI-PMH is frequently used by digital libraries for allowing metadata to be harvested. A benefit to this approach is that the search mechanism has full control over indexing and ranking algorithms, possibly allowing more consistent results. A drawback is that harvesting and indexing systems are more resource-intensive and therefore expensive.

[edit] Construction and organisation

[edit] Frameworks

A digital library can be built around specific repository software. The best known examples of this are DSpace, Eprints, Fedora, dLibra, and Greenstone Digital Library Software.

[edit] Selection Criteria

A strategy with defined selection priorities for digitization is critical and should be informed by a convergence in the consideration for both preservation and access. The focus should be based on traditional preservation decisions such as the value of materials; the condition of materials; use of materials; and material characteristics ensuring a high level of success. For the Library of Congress, items of national interest are prime candidates and digitizing these objects improves access while reducing the wear and tear on the originals.[1]

In the early discussions about digitization of library materials the selection decisions were proposed based on a desire for better access to that item's content and not on the condition or value of the original item.[5] In 2001, Paula De Stefano[6] wrote that a use-based criteria was promising, as it is “fundamental to collection development and is the common thread in all selection decisions” however her own study showed that use was not the most popular approach – in fact, most digital projects at the time focused on special collections, which are generally not the most popular items in the overall collection.

The persistent risk of disappearing "last copies".[7] and the declines seen in the condition of national treasures, as exemplified by the 2005 Heritage Health Index Report on the State of America's Collections[8] provide the rationale for establishing priorities and balancing access with preservation needs. The transient nature of electronic information can contribute to a phenomenon called "memory loss." This is a result of data extinctions as technologies become obsolete. There is also a drift away from original bibliographic contexts as time passes.[9] A 1998 Council on Library and Information Sources white paper[2] identified the following comprehensive considerations for selection: assessment of the intellectual and physical nature of the source materials; the number and location of current and potential users; the current and potential nature of use; the format and nature of the proposed digital product and how it will be described, delivered, and archived; how the proposed product relates to other digitization efforts; and projections of costs in relation to benefits.

[edit] Digitization

Digitization is the process of representing an object, an image, or a signal (usually an analog signal) by a discrete set of its points or samples. The result is called "digital representation" or, more specifically, a "digital image", for the object, and "digital form", for the signal.

Analog signals are continuously variable, both in the number of possible values of the signal at a given time, as well as in the number of points in the signal in a given period of time. However, digital signals are discrete in both of those respects, and so a digitization can only ever be an approximation of the signal it represents. The digital representation does not necessarily lose information in this transformation since the analog signal usually contains both information and noise.

A digital signal may be represented by a sequence of integers. Digitization is performed by reading an analog signal A, and, at regular time intervals (sampling frequency), representing the value of A at that point by an integer. Each such reading is called a sample.

A series of integers can be transformed back into an analog signal that approximates the original analog signal. Such a transformation is called DA conversion. There are two factors determining how close such an approximation to an analog signal A a digitization D can be, namely the sampling rate and the number of bits used to represent the integers.

In the past few years, procedures for digitizing books at high speed and comparatively low cost have improved considerably with the result that it is now possible to plan the digitization of millions of books per year for creating digital libraries.[10]

[edit] Collaborative digitization projects

There are many collaborative digitization projects throughout the United States and in Europe, Australia and Asia (see below). Two of the earliest projects were the Collaborative Digitization Project in Colorado and NC ECHO - North Carolina Exploring Cultural Heritage Online, based at the State Library of North Carolina. These projects helped to establish and publish best practices for digitization and work with regional partners to digitize cultural heritage materials. Additional criteria for best practice have more recently been established in the UK, Australia and the European Union.[11] Wisconsin Heritage Online is a collaborative digitization project modeled after the Colorado Collaborative Digitization Project. Wisconsin uses a wiki to build and distribute collaborative documentation. Georgia's collaborative digitization program, the Digital Library of Georgia, presents a seamless virtual library on the state's history and life, including more than a hundred digital collections from 60 institutions and 100 agencies of government. The Digital Library of Georgia is a GALILEO initiative based at the University of Georgia Libraries.

[edit] Advantages

The advantages of digital libraries as a means of easily and rapidly accessing books, archives and images of various types are now widely recognized by commercial interests and public bodies alike.[12] You can also acces any user account simply through a link like this.

Traditional libraries are limited by storage space; digital libraries have the potential to store much more information, simply because digital information requires very little physical space to contain it. As such, the cost of maintaining a digital library is much lower than that of a traditional library. A traditional library must spend large sums of money paying for staff, book maintenance, rent, and additional books. Digital libraries do away with these fees.

Digital libraries can immediately adopt innovations in technology providing users with improvements in electronic and audio book technology as well as presenting new forms of communication such as wikis and blogs. An important advantage to digital conversion is increased accessibility to users. There in also availability to individuals who may not be traditional patrons of a library, due to geographic location or organizational affiliation.

  • No physical boundary. The user of a digital library need not to go to the library physically; people from all over the world can gain access to the same information, as long as an Internet connection is available.
  • Round the clock availability. A major advantage of digital libraries is that people can gain access to the information at any time, night or day.
  • Multiple access. The same resources can be used simultaneously by a number of institutions and patrons
  • Information retrieval. The user is able to use any search term (word, phrase, title, name, subject) to search the entire collection. Digital libraries can provide very user-friendly interfaces, giving clickable access to its resources.
  • Preservation and conservation.Digitization is not a long-term preservation solution for physical collections, but does succeed in providing access copies for materials that would otherwise fall to degradation from repeated use. Digitized collections and born-digital objects pose many preservation and conservation concerns that analog materials do not. Please see the following "Problems" section of this page for examples.
  • Space. Whereas traditional libraries are limited by storage space, digital libraries have the potential to store much more information, simply because digital information requires very little physical space to contain them and media storage technologies are more affordable than ever before.
  • Added value. Certain characteristics of objects, primarily the quality of images, may be improved. Digitization can enhance legibility and remove visible flaws such as stains and discoloration.[13]

[edit] Problems

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With the ever-expanding digital collections in today’s library’s and archives we are facing new preservation challenges that seem to have no concrete solutions or universal standards in which to guide us. For centuries we have seen the evolution of paper based materials and have been able to successfully meet many of the challenges that these materials present to the realm of preservation. Our digital world, however, is far too young and mercurial to have any long-term sense of how this new media can be preserved for long-term future access.

On one hand multiple copies of a physical volume can exist in different libraries, but can only be viewed by visiting the library or repository directly. On the other hand, a digital object can be viewed from multiple locations but more than likely exists only as a single copy in a single location on one server.[14] Access to digital libraries and their collections is dependent upon a stable information technology infrastructure (power, computers, communications links etc.). Hence, despite the egalitarian potential of the digital library, many of those who could most benefit from its global reach (for instance in the Third World) are not able to do so. Smaller libraries and repositories in developed countries may also have limited resources in dealing with long term digitization projects. There are complex technological steps involved with capturing images, and librarians must evaluate the ability to commit to long term projects.[15]

Technological standards change over time and forward migration must be a constant consideration of every library. Migration is a means of transferring an unstable digital object to another more stable format, operating system, or programming language.[16] Migration allows the ability to retrieve and display digital objects that are in danger of becoming extinct. This is a rather successful short-term solution for the problem of aging and obsolete digital formats, but with the ever-changing nature of computer technologies, migration becomes this never-ending race to transfer digital objects to new and more stable formats. Migration is also flawed in the sense that when the digital files are being transferred, the new platform may not be able to capture the full integrity of the original object.[17] There are countless artifacts sitting in libraries all over the world that are essentially useless because the technology required to access the source is obsolete.In addition to obsolescence, there are rising costs that result from continually replacing the older technologies. This issue can dominate preservation policy and may put more focus on instant user access in place of physical preservation.[18]

Some people have criticized that digital libraries are hampered by copyright law, because works cannot be shared over different periods of time in the manner of a traditional library. There is a dilution of responsibility that occurs as a result of the spread-out nature of digital resources. Complex intellectual property matters may become involved since digital material isn't always owned by a library.[19] The content is, in many cases, public domain or self-generated content only. Some digital libraries, such as Project Gutenberg, work to digitize out-of-copyright works and make them freely available to the public. An estimate of the number of distinct books still existent in library catalogues from 2000BC to 1960, has been made. [3][20]

Other digital libraries accommodate copyright concerns by licensing content and distributing it on a commercial basis, which allows for better management of the content's reproduction and the payment (if required) of royalties. The Fair Use Provisions (17 USC § 107) under copyright law provide specific guidelines under which circumstances libraries are allowed to copy digital resources. Four factors that constitute fair use are purpose of use, nature of the work, market impact, and amount or substantiality used.[21]

[edit] Intellectual Property and Art Digitization

The ease of digital reproduction has pushed art institutions into a more conservative stance on the issue of intellectual property rights (much in the same vein as it did the music industry.) But to whom do what the J. Paul Getty Museum’s Kenneth Hamma labels “public-domain works of art” belong? Public domain works that are too old to be included in ongoing copyright protection, yet still remain out of the public’s view and also “of educators, and of the general milieu of creativity”.

A museum’s decision to guard this information hinders research and halts digitization efforts. If the Internet fosters the free-exchange of ideas for the sake of educational access, then these assertions undermine the mission of the museum and more general of digitization. Still, some proponents of intellectual property claim that controlling ownership of public domain artwork generates revenue through licensing fees, and this accrued funding directly benefits institutional operation, but no publicly available statistical data to effectuate this belief exists.

Excluding fiscal concerns, institutions often assume the role of guide and seek control over educational usage, thereby influencing the creative processes that result from these visual resources. For instance, an art historian developing critical theory on a particular issue in the Dutch Renaissance may be granted usage of certain works and not others as decreed by the curatorial interpretations of museum staff. This practice narrows the possibility for a unique, fresh perspective somewhat by limiting the intellectual freedom of the scholar.

The issue overlaps other digitization obstacles that initiate debate in the arts community. For example, the usage of digital images for physical reproduction of artwork presents a common problem and also provides a more relatable model for those just beginning to grasp digitization. Few people take offense to Impressionist works featured on stationery sets, umbrellas, canvas tote bags and the like.

An ethical obligation to retain rights on certain pieces may validate relinquishing accessibility. In spite of the current intellectual property rights issues, perhaps both leaps in technology and the ideas of Kenneth Hamma and his like-minded colleagues will inspire a growing acceptance and ultimate embrace of digitization.

[edit] References

  1. ^ Greenstein, Daniel I., Thorin, Suzanne Elizabeth. The Digital Library: A Biography. Digital Library Federation (2002) ISBN 1933645180. Accessed June 25, 2007.
  2. ^ Kahn, R. E., & Cerf, V. G. (1988). The Digital Library Project Volume I: The World of Knowbots, (DRAFT): An Open Architecture For a Digital Library System and a Plan For Its Development. Reston, VA: Corporation for National Research Initiatives.
  3. ^ Edward A. Fox. The Digital Libraries Initiative - Update and Discussion, Bulletin of the America Society of Information Science, Vol. 26, No 1, October/November 1999.
  4. ^ Koehler, AEC. Some Thoughts on the Meaning of Open Access for University Library Technical Services Serials Review Vol. 32, 1, 2006, p. 17
  5. ^ Gertz, J. (2000 April). Selection for preservation in the digital age: An overview. Library Resources & Technical Services, 44(2), 97-104.
  6. ^ De Stefano, Paula. (2001, January). Selection for digital conversion in academic libraries. College & Research Libraries 62(1), 58-69.
  7. ^ Silipigni Connaway, L, et. als. (2006, July). Last copies: What's at risk?. College & Research Libraries, 67(4), 370-9.
  8. ^ Heritage Preservation, 2005. A Public Trust at Risk: The Heritage Health Index Report on the State of America’s Collections. Washington, D.C.: Heritage Preservation
  9. ^ Teper, Thomas H. "Where Next? Long-Term Considerations for Digital Initiatives." Kentucky Libraries. 65(2) (2001):12-18.
  10. ^ Committee on Institutional Cooperation: Partnership announced between CIC and Google, 6 June 2007, Retrieved 7 July 2007.
  11. ^ Digital Libraries: Principles and Practice in a Global Environment, Ariadne April 2005.
  12. ^ European Commission steps up efforts to put Europe’s memory on the Web via a “European Digital Library” Europa press release, 2 March 2006
  13. ^ Gertz, Janet. "Selection for Preservation in the Digital Age." Library Resources & Technical Services. 44(2) (2000):97-104.
  14. ^ Cain, Mark. “Managing Technology: Being a Library of Record in a Digital Age”, Journal of Academic Librarianship 29:6 (2003).
  15. ^ Gertz, Janet. "Selection for Preservation in the Digital Age: An Overview." Library Resources & Technical Services 44(2) (2000):97-104.
  16. ^ Cain, Mark. “Managing Technology: Being a Library of Record in a Digital Age”, Journal of Academic Librarianship 29:6 (2003).
  17. ^ Breeding, Marshall. “Preserving Digital Information.”. Information Today 19:5 (2002).
  18. ^ Teper, Thomas H. "Where Next? Long-Term Considerations for Digital Initiatives." Kentucky Libraries 65(2)(2001):12-18.
  19. ^ Pymm, Bob. "Building Collections for All Time: The Issue of Significance." Australian Academic & Research Libraries. 37(1) (2006):61-73.
  20. ^ Kelly, Kevin. "Scan This Book!", New York Times Magazine, 2006-05-14. Retrieved on 2008-03-07. "When Google announced in December 2004 that it would digitally scan the books of five major research libraries to make their contents searchable, the promise of a universal library was resurrected. ... From the days of Sumerian clay tablets till now, humans have "published" at least 32 million books, 750 million articles and essays, 25 million songs, 500 million images, 500,000 movies, 3 million videos, TV shows and short films and 100 billion public Web pages." 
  21. ^ Stanford Copyright & Fair Use - Digital Preservation and Copyright by Peter B. Hirtle

[edit] See also

[edit] External links

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[edit] General

[edit] Conferences

  • ECDL - European Conference on Digital Libraries
  • ICADL - International Conference on Asian Digital Libraries
  • JCDL - ACM and IEEE Joint Conference on Digital Libraries

[edit] National and international archives

[edit] Book archives

[edit] Major subject archives

[edit] Tools