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. The term digital libraries (plural) is also used for the academic subdiscipline that studies digital libraries. The digital content may be stored locally, or accessed remotely via computer networks. The term digital libraries was first made popular by the NSF/DARPA/NASA Digital Libraries Initiative in 1994. The older names electronic library or virtual library are also used.
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[edit] Digitizing
Digitizing or digitization is 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.
[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 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.
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 have both physical collections and digital collections. 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] Advantages
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.
- 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 accesses. The same resources can be used at the same time by a number of users.
- Structured approach. Digital libraries provide access to much richer content in a more structured manner, i.e. we can easily move from the catalog to the particular book then to a particular chapter and so on.
- Information retrieval. The user is able to use any search term bellowing to the word or phrase of the entire collection. Digital libraries can provide very user-friendly interfaces, giving clickable access to its resources.
- Preservation and conservation. An exact copy of the original can be made any number of times without any degradation in quality.
- 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. When a library has no space for extension digitization is the only solution.
- Networking. A particular digital library can provide a link to any other resources of other digital libraries very easily; thus a seamlessly integrated resource sharing can be achieved.
- Cost. In theory, the cost of maintaining a digital library is 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. Although digital libraries do away with these fees, it has since been found that digital libraries can be no less expensive in their own way to operate. Digital libraries can and do incur large costs for the conversion of print materials into digital format, for the technical skills of staff to maintain them, and for the costs of maintaining online access (i.e. servers, bandwidth costs, etc.). Also, the information in a digital library must often be "migrated" every few years to the latest digital media. This process can incur very large costs in hardware and skilled personnel.(See data migration).
- In further discussion of cost The Science and Technology Departments may have to begin thinking about new technological programs for seniors and how they will fund them. Because of the growing senior population, some of the cost of maintaining technology in libraries as we know them today, and the now burgeoning digital libraries more monies will have to be spent 0n programs for seniors. Programs such as Basic learning of a computer, Word part one, two, three and four. Excel part one and two;Classes on how to use the Internet and how to E-mail. These are just a few that will help bring seniors into the twenty-first century technologically.
In February 2004 a survey was taken and Americans sixty-five and older reported having access to a computer at home, or daily use of a computer at their local library. The local library in my community in the Northwest suburb of Chicago boasts forty-six computers in the main area of the adult department, and fifteen computers in the computer lab, all wired for use of the Internet. Wireless is also provided for those having laptops. Classes to learn computer skills are available for seniors of the area all year round as well.
Seniors seem to be most interested in using the Internet to get on search engines to help them get answers to specific questions regarding insurance benefits, social security. They are also able to serach sites that give them information about doctors, lawyers, organizations helping seniors, stores and much more. Computers assists the senior to live a better informed and healthy life both physicially and emotionally because of the information that is readily available to them using technology.
The fact that the Internet is available around the clock, has no physical boundaries, allows the patro no matter the age, to work from home or their local library. This is a huge benefit to the community. It allows the patron to communicate in a much larger area of searching to get the information they are looking for.
"Baby Boomers" are changing the way we view seniors and technology. They are part of the "wired seniors". Their technological behavior is not that distinguishable from the thirty-year-old computer user. These seniors will come to be known as the "silver tsunami". There is, however, still a large group over sixty-five that are not only non-users, never been on line or don't know anyone who has been an Internet user. This group of seniors probably if asked, have a more traditional view of a library and will never use a computer in their lifetime.
For the present technologically active seniors are a big part of the ever changing scene of the community library and their numbers are growing. The Science and Technology Departments of our community libraries need to be aware of this and may have to set aside part of their annual budget to accommodate the demands and needs of this growing group of patrons.
[edit] Problems
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. 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 [1].
Other digital libraries (more specifically, digital collections, which may be acquired by 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.
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.
[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. Many of these repositories are made available to the academic community or, sadly for the true aims of societal non-profits, only rarely, the general public. Insitutional, 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:
- 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);
- 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);
- 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 and 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] 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 can also use OAI-PMH to find these deep web resources.
There are two general strategies for searching a federation of digital libraries:
- distributed searching, and
- 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. Scalability and performance issues tend to plague distributed searching for large federations of digital libraries. Protocols like Z39.50 are frequently used in distributed searching.
Searching over previously harvested metadata requires the pooling of metadata collected from every digital library in the federation. This solution scales better than distributed search, but it introduces the problem of data freshness; digital libraries need to be re-harvested on a periodic basis to discover new and updated resources. OAI-PMH is frequently used by digital libraries for harvesting metadata.
[edit] Framework
A digital library is built around specific repository software. The best known examples of it are DSpace, Eprints, Fedora (software)Fedora or dLibra, or Greenstone Digital Library Software ,
[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] See also
- The European Library
- Alphabetical List of Digital Libraries (Wikipedia)
- e-Book
- Electronic journal
- ePrint
- List of digital library projects
- Institutional Repository
- National repository
- Open Archives Initiative Protocol for Metadata Harvesting
- Open Content Alliance
- Repository (publishing)
- Storage Resource Broker
- Universal library
- Dynamic web page
[edit] External links
[edit] General
Digital library article at LISWiki, a Library and information science wiki
- Malte Herwig; "Putting The World's Books On The Web"
- BRICKS Building Resources for Integrated Cultural Knowledge Services
- www.delos.info DELOS - Network of Excellence on Digital Libraries
- CNRI-DARPA: D-Lib Magazine Electronic publication that primarily focuses on digital library research and development
- DLI Digital Libraries Initiative web page
- The Scope of the Digital Library
- Online version of Internetworking Technologies by Rahul Banerjee
Deals with the architectures of leading digital libraries in the world (chapter 10)
[edit] National and international archives
- UK Higher Education & Research Libraries - A link list maintained at Exeter University by Ian Tilsed
- National Science Digital Library (NSDL)
Online library of resources for science, technology, engineering, and mathematics education and research - Akhter Hameed Khan Digital Library - Islamabad by Ata ur Rehman
- Azerbaijan Electronic Library Network (Kitab.Az) Azerbaijan's online network of electronic catalogues
- The eGranary Digital Library Millions of digital resources for those with inadequate Internet connectivity
- PIONIER Digital Libraries - Network of digital libraries in Poland
[edit] Regional and university archives
- MIT Press: Digital Libraries by William Y. Arms
[edit] Book archives
- UPenn: The Online Books Page Search for free online books by author, title, keyword, etc.
- The Internet Public Library Search for free online books by author, title, keyword, etc.
[edit] Major subject archives
- The American Journeys Project a digital library whose contents center on --the exploration of North America.
- European Navigator: The first Digital Library on the history of the European Union
- dLIST dLIST: Digital Library of Information Science and Technology, an open access archive of Information Sciences materials
- ETANA - Electronic Tools and Ancient Near Eastern Archives Electronic library for the Ancient Near East
- Kabbalah Digital Library One of the largest multi-language collections of ancient and modern Kabbalistic writings.
- The International Children's Digital Library
- OpenMED@NIC Open access archive of Medical and Allied Sciences. .
[edit] Tools
- University of Southampton: E-Prints for Digital Repositories
- MIT & HP: DSpace digital repository
- UNESCO: Greenstone Digital Library Software
- Search engines that include public digital libraries
- DL-Harvest DL-Harvest, an open access aggregator for Information Sciences
- BRICKS Framework BRICKS open-source framework for Digital Libraries
