Several aspects of these definition

Several aspects of these definitions should be noted. One is that digital libraries are viewed as databases, albeit databases of rich content, whether full text, images, or combinations of media and representations. Much digital library research, particularly that conducted in departments of computer science, focuses on `enabling technologies' such as database structure,retrieval algorithms, filtering, intelligent agents, network architecture and other necessary capabilities.

These definitions assume or require that content is collected on behalf of a user community.This aspect of the definition frames digital libraries in terms of their users, which also determines the tools and capabilities those users need to manipulate the content. Digital library research on information needs and uses, users, interface design and social context derives from these aspects of the definitions. The one deinition that mentions institutions indicates that digital libraries can be extensions of libraries, museums, archives and schools, as well as extensions of work, education and leisure environments in which information resources are used. The notion of `community' remains problematic, as none of these definitions provide criteria for identifying or determining the scope of a user community.

Another noteworthy assumption, particularly in definitions originating in the U.S., is that digital libraries exist in distributed environments. This is not surprising, given that the U.S.digital libraries initiatives are closely related to information infrastructure development (Office of Science and Technology Policy, 1994; National Science and Technology Council, 1998). The DLI-1 (National Science Foundation, 1993) call for proposals begins by defining the Internet and setting the need for DL research in a network context. By the time DLI-2 was announced five years later (National Science Foundation, 1998), technical issues of operating digital libraries on computer networks had become core research concerns. These include interoperability, portability, data exchange, scalability, federation, extensibility and open network architectures.