DIGITAL LIBRARY:
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][not in citation given]The
digital content may be stored locally, or accessed remotely via computer
networks. A digital library is a type of information retrieval system.
In the context of the DELOS, a Network of Excellence on
Digital Libraries, and DL.org, a Coordination Action on Digital
Library Interoperability, Best Practices and Modelling Foundations, Digital
Library researchers and practitioners produced a Digital Library Reference
Model[2][3]
which defines a digital library as: "A potentially virtual organisation,
that comprehensively collects, manages and preserves for the long depth of time
rich digital content, and offers to its targeted user communities specialised
functionality on that content, of defined quality and according to
comprehensive codified policies."[4]
The first use of the term digital
library in print may have been in a 1988 report to the Corporation for National
Research Initiatives[5][not in citation given]
The term digital libraries was first popularized by the NSF/DARPA/NASA Digital Libraries
Initiative in 1994.[6]
These draw heavily on As We May Think by Vannevar
Bush in 1945, which set out a vision not in terms of technology, but user
experience.[7]
The term virtual library was initially used interchangeably with digital
library, but is now primarily used for libraries that are virtual in other
senses (such as libraries which aggregate distributed content).
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. For example, American
Memory is a digital library within the Library of Congress. Some important digital
libraries also serve as long term archives, such as arXiv and the Internet
Archive.
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, in contrast to the publication of
research in commercial journals, where the publishers often limit access
rights. Institutional, truly free, and corporate repositories are sometimes
referred to as digital libraries.
Digital archives
Physical archives differ
from physical libraries in several ways. Traditionally, archives are 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,
periodicals, etc.).
2.
Having their contents organized in
groups rather than individual items.
3.
Having unique contents.
The technology used to create digital libraries is even more
revolutionary for archives since it breaks down the second and third of these
general rules. In other words, "digital archives" or "online
archives" will still generally contain primary sources, but they are
likely to be described individually rather than (or in addition to) in groups
or collections. Further, because they are digital their contents are easily
reproducible and may indeed have been reproduced from elsewhere. The Oxford Text Archive is generally considered to be the oldest digital archive of
academic physical primary source materials.
The future
Large scale digitization projects are underway at Google, the Million Book Project, and Internet Archive.
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. Just as libraries
have ventured into audio and video collections, so have digital libraries such
as the Internet Archive.
According to Larry Lannom, Director of Information
Management Technology at the nonprofit Corporation should be for National
Research Initiatives, "all the problems associated with digital libraries
are wrapped up in archiving." He goes on to state, "If in 100 years
people can still read your article, we'll have solved the problem." Daniel
Akst, author of The Webster Chronicle, proposes that "the future of
libraries — and of information — is digital." Peter Lyman and Hal Varian,
information scientists at the University
of California, Berkeley, estimate
that "the world's total yearly production of print, film, optical, and magnetic
content would require roughly 1.5 billion gigabytes of storage."
Therefore, they believe that "soon it will be technologically possible for
an average person to access virtually all recorded information."[8]
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,
Yahoo! and Scirus can also use OAI-PMH to find these deep web resources.[9]
There are two general strategies for searching a federation
of digital libraries:
1.
distributed searching, and
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.
Frameworks
The formal reference models include the DELOS Digital
Library Reference Model (Agosti, et al., 2006)[10]
and the Streams, Structures, Spaces, Scenarios, Societies (5S) formal
framework.[11]
The Reference Model for an Open Archival Information System (OAIS) provides a framework to address digital preservation.[12]
Construction and organization
Digital Collections Selection
Criteria are applied by organisations
(typically libraries) creating a digital library
which of their existing holdings and forth-coming acquisitions to digitise for
inclusion.
A strategy with defined selection
priorities for digitization is critical, and should consider both preservation
and access. factors to consider are:
- 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 were prime candidates both to improve access and
reduce wear and tear on the physical copies.[1]
In the early discussions about
digitization of library materials the selection decisions were often proposed
based on a desire for better access to that item's content, and not on the
condition or value of the original item.[2]
In 2001, Paula De Stefano[3]
wrote that a use-based group of criteria was promising, as it is “fundamental
to collection development and is the common thread in all selection decisions”.
In practice, however, her study showed that most digital projects focused on
special collections, which are generally not the most popular items in the
overall collection.
The persistent risk of disappearing
"last copies".[4]
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[5]
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.[6]
Software
There are a number of software packages for use in general
digital libraries, for notable ones see Digital
library software. Institutional repository software,
which focuses primarily on ingest, preservation and access of locally produced
documents, particularly locally produced academic outputs, can be found in Institutional
repository software.
Digitization
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 digitize millions of books per year.[13]
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.[14]
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 can be much lower than that of a
traditional library. A physical library must spend large sums of money paying
for staff, book maintenance, rent, and additional books. Digital libraries may
reduce or, in some instances, do away with these fees. Both types of library
require cataloguing input to allow users to locate and retrieve material.
Digital libraries may be more willing to 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; conventional
libraries may consider that providing online access to their OPAC catalogue is
sufficient. An important advantage to digital conversion is increased
accessibility to users. They also increase 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 24/7 to the information.
·
Multiple
access. The same resources can be used
simultaneously by a number of institutions and patrons. This may not be the
case for copyrighted material: a library may have a license for "lending
out" only one copy at a time; this is achieved with a system of digital
rights management where a resource can become
inaccessible after expiration of the lending period or after the lender chooses
to make it inaccessible (equivalent to returning the resource).
·
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.[15]
·
Easily
accessible.
Challenges
|
This article's tone
or style may not reflect the encyclopedic tone used on Wikipedia. Specific concerns may be found on the talk page. See Wikipedia's guide
to writing better articles
for suggestions. (May 2008)
|
Digital preservation
Main article: Digital preservation
Digital preservation aims to ensure that digital media and
information systems are still interpretable into the indefinite future. Each
necessary component of this must be migrated, preserved or emulated.[16]
Typically lower levels of systems (floppy disks
for example) are emulated, bit-streams (the actual files stored in the disks)
are preserved and operating systems are emulated as a virtual machine.
Only where the meaning and content of digital media and information systems are
well understood is migration possible, as is the case for office documents.[16][17][18]
However, at least one organization, the WiderNet Project,
has created an offline digital library, the eGranary, by
reproducing materials on a 4 TB hard drive.
Instead of a bit-stream environment, the digital library contains a built-in proxy server
and search engine so the digital materials can be accessed using an Internet browser.[19]
Also, the materials are not preserved for the future. The eGranary is intended
for use in places or situations where Internet connectivity is very slow,
non-existent, unreliable, unsuitable or too expensive.
Copyright and licensing
Digital libraries are hampered by copyright
law because, unlike with traditional libraries, digital libraries do not have
access to works from every time period. The republication of material on the
web by libraries may require permission from rights holders, and there is a
conflict of interest between libraries and the publishers who may wish to
create online versions of their acquired content for commercial purposes. In
the year 2010 it was estimated that twenty-three percent of books in existence
were created before 1923 and thus out of copyright. Of those printed after this
date, only five percent were still in print as of 2010. Thus, approximately
seventy-two percent of books were not available to the public.[20]
There is a dilution of responsibility that occurs as a
result of the distributed nature of digital resources. Complex intellectual
property matters may become involved since digital material is not always owned
by a library.[21]
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 2000 BC to 1960, has been made.[22][23]
The Fair Use Provisions (17
USC § 107) under the Copyright Act of 1976 provide specific guidelines under which circumstances
libraries are allowed to copy digital resources. Four factors that constitute
fair use are "Purpose of the use, Nature of the work, Amount or
substantiality used and Market impact."[24]
Some digital libraries acquire a license to lend their
resources. This may involve the restriction of lending out only one copy at a
time for each license, and applying a system of digital
rights management for this purpose (see also above).
The Digital
Millennium Copyright Act of 1998
was an act created in the United States to attempt to deal with the
introduction of digital works. This Act incorporates two treaties from the year
1996. It criminalizes the attempt to circumvent measures which limit access to
copyrighted materials. It also criminalizes the act of attempting to circumvent
access control.[25]
This act provides an exemption for nonprofit libraries and archives which
allows up to three copies to be made, one of which may be digital. This may not
be made public or distributed on the web, however. Further, it allows libraries
and archives to copy a work if its format becomes obsolete.[26]
Copyright issues persist. As such, proposals have been put
forward suggesting that digital libraries be exempt from copyright law.
Although this would be very beneficial to the public, it may have a negative
economic effect and authors may be less inclined to create new works.[27]
Metadata creation
In traditional libraries, the ability to find works of
interest was directly related to how well they were catalogued. While
cataloguing electronic works digitized from a library's existing holding may be
as simple as copying or moving a record from the print to the electronic form,
complex and born-digital works require substantially more effort. To handle the
growing volume of electronic publications, new tools and technologies have to
be designed to allow effective automated semantic classification and searching.
While full text search can be used for some searches, there are many common
catalog searches which cannot be performed using full text, including:
·
finding texts which are translations
of other texts
·
linking texts published under
pseudonyms to the real authors (Samuel Clemens
and Mark Twain,
for example)
No comments:
Post a Comment