Digital Libraries

Digital Libraries

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.

Technological Issues

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.

see also Data Mining; Database Management Software; Information Technology Standards; Library Applications.

Edie Rasmussen

Bibliography

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.