"An informal definition of a digital library is a managed collection of information, with associated services, where the information is stored in digital formats and accessible over a network. A crucial part of this definition is that the information is managed. A stream of data sent to earth from a satellite is not a library. The same data, when organized systematically, becomes a digital library collection. Most people would not consider a database containing financial records of one company to be a digital library, but would accept a collection of such information from many companies as part of a library. Digital libraries contain diverse information for use by many different users. Digital libraries range in size from tiny to huge. They can use any type of computing equipment and any suitable software. The unifying theme is that information is organized on computers and available over a network, with procedures to select the material in the collections, to organize it, to make it available to users, and to archive it."
There are many definitions of a "digital library." Terms such as "electronic library" and "virtual library" are often used synonymously. The elements that have been identified as common to these definitions are:
The working definition of digital library used by the CDLM is as follows:
A digital library is a collection of collections of electronic knowledge resources developed and maintained in order to meet the totality of information needs for a given user population.
An organized collection of selected digital resources created to support scholarship, research and teaching.
Through the use of appropriate technological standards, a Digital Library is created to facilitate permanent
access to and resource discovery of selected digital resources.
The Digital Library is:
The collection of services
And the collection of information objects
That support users in dealing with information objects
And the organization and presentation of those objects
Available directly or indirectly
Via electronic/digital means.
Providing a definition of the term "digital library" is difficult; even a recently published dictionary may not give a good one-sentence definition. In part, this confusion comes from the fact that "digital library" can mean different things to different people, depending on their perception of the concept. For example, someone with a background in computer science may view a digital library as networked or distributed information system, while a librarian may define a digital library as a digital counterpart of the physical library. Actually, a digital library may encompass either of these concepts.
Here are a few definitions of the term that have been drawn from various sources.
Digital libraries are organizations that provide the resources, including the specialized staff, to select, structure, offer intellectual access to, interpret, distribute, preserve the integrity of, and ensure the persistence over time of collections of digital works so that they are readily and economically available for use by a defined community or set of communities (Digital Library Federation, par. 1).
A library that maintains all, or a substantial part, of its collection in computer-accessible form as an alternative, supplement, or complement to the conventional printed and microfilm materials that currently dominate library collections. Used in this context, the term "collection" denotes the documents that a library acquires or maintains (Saffady, 224).
Digital libraries are a set of electronic resources and associated technical capabilities for creating, searching, and using information. In this sense they are an extension of information storage and retrieval systems that manipulate digital data in any medium (text, images, sounds; static or dynamic images) and exist in distributed networks. The content of digital libraries includes data, metadata that describe various aspects of the data, . . . and metadata that consist of links or relationships to other data and metadata, whether internal or external to the digital library (Borgman et al., "Introduction" par. 4).
While these definitions share some characteristics, they all reflect a slightly different focus. Perhaps at its most basic level, a digital library may be defined as a collection of digital resources selected according to certain criteria and made accessible for retrieval over computer networks. Various types of digital information may be incorporated into the collection, including both retrospectively converted printed materials and materials that exist only in digital form, as well as a broad range of material formats, including books, journals, sound recordings, pictures, and video.