The broad goal of the Digital Libraries Initiative
is to dramatically advance the means to collect, store, organize, and use
widely distributed knowledge resources containing diverse types of information and content
stored in a variety of electronic forms.
(DLI Interagency Coordinating Committee, in Fox and Urs 2002:509)

Streams: sequences of elements
Structures: arrangement and organization
Spaces: objects and rule-based operations
Scenarios: services performed
Societies: communities, individual users
(Fox and Urs 2002:519)