Digital libraries are organized collections of information resources and associated tools for creating, archiving, sharing, searching, and using information that can be accessed electronically. Digital libraries differ from traditional libraries in that they exist in the "cyber world" of computers and the Internet rather than in the "brick and mortar world" of physical buildings. Digital libraries can store any type of information resource (often referred to as documents or objects) as long as the resource can be represented electronically. Examples include hypertexts, archival images, computer simulations, digital video, and, most uniquely, real-time scientific data such as temperature readings from remote meteorological instruments connected to the Internet.
The digitization of resources enables easy and rapid access to, as well as manipulation of, digital library content. The content of a digital library object (such as a hypertext of George Orwell's novel, 1984) includes both the data inherent in the nature of the object (for example, the text of 1984) and metadata that describe various aspects of the data (such as creator, owner, reproduction rights, and version). Both data and metadata may also include links or relationships to other data or metadata that may be internal or external to any specific digital library (for instance, the text of 1984 might include links to comments by readers derived from a literary listserv or study notes provided by teachers using the novel in their classes).
The concepts of organization and selection separate digital libraries from the Internet as a whole. Whereas information on the Internet is chaotic and expanding faster than either humans or existing technologies can trace accurately, the information in a digital library has been organized in some manner to provide the resource collection, cataloging, and service functions of a traditional library. In addition, the resources in digital libraries have gone through some sort of formal selection process based on clear criteria, such as including only resources that come from original materials or authoritative sources. Digital libraries are thus an effort to address the problem of information overload often associated with the Internet.
Although the concept of digital libraries has been traced back to nineteenth-century scientific fiction writers such as H. G. Wells, most library historians credit Vannevar Bush's description of the memex in the July 1945 edition of Atlantic Monthly as the original source. Despite being limited to analog technologies such as microfilm that seem crude in the early twenty-first century, Bush anticipated several key features of digital libraries, including rapid and accurate access to scientific and cultural information.
Contemporary conceptions of digital libraries developed in tandem with the rapid growth of the Internet and especially the widespread, flexible access to digital information afforded by the development of World Wide Web browsers in the early 1990s. For example, in the United States, Phase One of the Digital Libraries Initiative was launched in 1993 when the National Science Foundation (NSF), the Defense Advanced Research Projects Agency (DARPA), and the National Aeronautics and Space Administration (NASA) provided six universities with nearly $25 million to develop digital library test-beds. Another pioneer digital library effort was the U.S. Library of Congress's American Memory project. This groundbreaking digital collection of historical artifacts was first made available on interactive videodiscs, later on CD-ROMs, and most recently via the Internet. Related digital library projects have been underway in Europe, Canada, and elsewhere since the mid-1990s.
In 1998 Phase Two of the Digital Libraries Initiative (DLI2) was launched with funding from NSF, DARPA, NASA, the Library of Congress, the National Library of Medicine, the National Endowment for the Humanities (NEH), and the Federal Bureau of Investigation (FBI). The seemingly strange bedfellows supporting DLI2 suggests some of the ethical issues surrounding digital libraries. These include privacy (who can find out about the resources someone has accessed via digital libraries?), security (who decides what information should or should not be freely accessible?), intellectual property (who owns what information?), hegemony (who controls the access to information?), and globalization (who assures that cultural identity is not weakened or even destroyed by digital libraries?).
Challenges: Technical and Ethical
The technical challenges confronting librarians, computer scientists, cognitive psychologists, and others working on the frontiers of digital libraries are formidable. These include interoperability (what protocols and standards are needed to ensure that distributed digital libraries will provide widespread interconnected access?), access (what types of user interfaces are most effective in providing easy access to diverse communities of users seeking information for different reasons?), preservation (what technologies are needed to assure the long-term survival of digital information resources?), and sustainability (what financial resources are needed to support the maintenance of digital libraries, and how can they be procured?).
In a manner similar to the science of genetics and the Human Genome Project, ethical debates about the ultimate status and value of information science and digital libraries may be even more complex than the technological challenges. It is inevitable that much information will be primarily available through digital technologies in the foreseeable future, a result that leads to complex social and ethical questions that must be addressed. How can traditional library values such as providing all people with free access to high-quality information be upheld when large corporations increasingly seek to profit by selling the information they control? Will the "digital divide" (that is, the unequal access to information technologies currently inherent in the growth of the Internet, which is largely controlled by Western powers such as the United States and the European Union) be decreased or increased by the development of digital libraries? How can the validity of information resources be established when increasingly sophisticated technologies threaten fundamental concepts such as authorship and copyright? How can digital libraries be designed to improve education at all levels?
In his 2000 book Digital Libraries, William Y. Arms concludes that "a dream of future libraries combines everything that we most prize about traditional methods with the best that online information can offer. In some nightmares, the worst aspects of each are combined" (p. 272). Although the future of digital libraries is unclear, digital libraries will nevertheless influence the future.
THOMAS C. REEVES
Arms, William Y. (2000). Digital Libraries. Cambridge, MA: MIT Press. This volume remains the definitive description of digital library concepts and structures.
Bush, Vannevar. (1945). "As We May Think." Atlantic Monthly 176(1): 101–108. This article has influenced several generations of the designers of hypertext, hypermedia, and digital libraries.
Arms, William Y. Digital Libraries. Available from http://www.cs.cornell.edu/wya/.
Bush, Vannevar. (1945). "As We May Think." Atlantic Monthly 176(1): 101–108. Available from http://www.theatlantic.com/unbound/flashbks/computer/bushf.htm.
"Digital Libraries Initiative Phase Two." National Science Foundation. Available from http://www.dli2.nsf.gov/.
U.S. Library of Congress. "American Memory: Historical Collections for the National Digital Library." Available from http://memory.loc.gov/.
The term "digital library" was coined relatively recently and is used to describe distributed access to collections of digital information. The terms "electronic library" and "virtual library" are sometimes also used. However, there is still considerable debate about the definition of a digital library because the term may mean different things to different groups. For example, sometimes it is used to refer to the content or collection of materials ("a digital library of historic photographs"), whereas at other times it refers to the institution or service provided ("the digital library provided electronic reference").
A unique characteristic of a digital library is that it is a collection of material organized for access by the users of the electronic documents. The material is in digital form and may consist of or incorporate various media, such as photographs, video, sound recordings, as well as text and page images. Access is provided through search engines that search the actual text of the materials, or more formal cataloging such as Library of Congress Classification or Subject Headings. Bibliographic and descriptive information about the contents is usually referred to as metadata , making the information accessible for use. Once users locate information in the form of digital documents, they are able to view or download them.
The users for whom the digital library is intended are a defined community or group of communities. They may be scattered around the world, or may be in the same geographical location but wish to access the information from off-site. Therefore, another key aspect of the digital library is that it can be accessed remotely, usually through a web browser. In general, the information contained in the World Wide Web is not considered to be a digital library (though it is sometimes referred to as such) because it lacks the characteristics of a collection organized for a specific purpose.
Because the development of digital libraries is a relatively new undertaking, research and development is being conducted even as new digital library projects are being launched. A number of organizations have taken a leadership role in integrating research and practice. For example, the National Science Foundation, along with other government bodies, funded a series of Digital Library Initiatives in order to help create a number of large-and medium-sized digital library projects with a research focus. The Association for Computing Machinery (ACM) and Institute of Electrical and Electronics Engineers (IEEE) sponsor the Joint Conference on Digital Libraries which brings together researchers and practitioners. The Institute of Museum and Library Services, a federal agency, provides funding for digital library projects at various levels. The Digital Library Federation is a consortium of libraries and organizations that attempt to identify standards and "best practices," coordinate research and development in the field, and initiate cooperative projects <http://www.diglib.org/dlfhomepage.htm>.
Advantages of the Digital Library
The digital library increases access to information in a number of ways. First, in many cases, the digital library allows documents to be searched based on content that is automatically indexed. This is true not only for text but also to some extent for images, video, and sound because content-based retrieval techniques have been developed to index digital characteristics such as image color and texture. Documents that have not received formal cataloging may still be located in a digital library, and even if cataloging information is available, the content-based information provides extra ways to search it. Once the relevant material has been found, access is again improved because the material can be viewed online, or even downloaded and viewed or printed at the user's location. This means that scholars need not travel to a distant library, or request an interlibrary loan. Instead, they have instantaneous access to the information at their desktop. Access is also improved because in many cases, through the medium of the World Wide Web, the information in the digital library is available not just to the local population, but to anyone who wishes to use it.
An additional advantage of the digital library is that because the digital information can be viewed and copied without access to the original document, it prevents wear and tear on library materials. This is particularly important when the original is valuable or fragile. The digital library, however, is not primarily concerned with preserving the original document because digitization changes the format of the document and the digital form itself may be difficult to preserve.
Types of Digital Libraries
There are many different types of digital libraries, ranging from simple collections to large-scale projects. The national libraries in many countries have been leaders in developing digital libraries of historical materials. In the United States, for example, the Library of Congress has an ongoing digital library project called "American Memory," which includes many historically important and interesting collections of photographs, sound recordings, and video. The materials are cataloged in ways similar to the library's physical collections in Washington, D.C., but, unlike those collections, they are available for viewing and downloading by anyone with a web browser and an Internet connection. The digital collection includes everything from baseball cards to Civil War photographs to video clips of Coca-Cola advertisements.
University and college libraries and many public libraries around the world are also undertaking digital library projects to make their materials more readily and widely available. The libraries of ten University of California campuses have initiated a "co-library," the California Digital Library, which provides access to faculty and students around the state. Materials include reference material such as encyclopedias and dictionaries, electronic journals, databases, and a "digital archive" of important manuscripts, photographs, and works of art held in libraries, museums, archives, and other institutions across California.
The enabling technologies for digital libraries are economical storage of large quantities of data, high-speed connectivity and networking, and technologies related to digitizing, indexing, retrieving, and using multimedia. As digital libraries evolve, many technological issues remain to be solved. Desirable characteristics of digital libraries are scalability, interoperability, and sustainability—they need to be able to grow, to interact with other digital libraries, and to continue to function as organizations and technologies change.
Builders of digital libraries consider the identification of standards important to ensure the smooth development and growth of their products. For example, standard formats are needed for digitization so digital products can be universally distributed and read. For content, metadata standards are needed for cataloging, and encoding standards for indicating. Because digital libraries are often federations of individual sites, standards for digital library architecture are also important. Often, an open architecture is specified, in which the digital library is considered to be a set of services and functions, with a specific protocol specifying what the interface to that function will be.
Social, Legal, and Economic Issues
In this new field, many questions related to social, legal, and economic issues need to be addressed. For instance, should digital materials be free? If not, what is an appropriate pricing model? Who owns digital materials? How does the copyright law in place for non-digital materials apply to digital images, sound, and text? How can intellectual property rights be protected, for example, through digital watermarks ? Is there a digital divide—do some people have the means and skills to access the digital library while others do not? How can privacy and security be ensured? These questions, like those of developing standards, are still open to research and debate.
Arms, W. Y. Digital Libraries. Cambridge, MA: MIT Press, 2000.
Borgman, C. L. From Gutenberg to the Global Information Infrastructure: Access to Information in the Networked World. Cambridge, MA: MIT Press, 2000.
Lesk, M. Practical Digital Libraries. San Francisco, CA: Morgan-Kaufman, 1997.
Impact of Digital Libraries
IMPACT OF DIGITAL LIBRARIES
Digital libraries, which provide widespread access to collections of electronic materials, are changing popular and scholarly use of textual and multimedia information. Their continued growth depends on the solution of technological problems, particularly the development of standards, as well as underlying legal, social, and economic questions.